1999 Catalog of Practical Papers

Design and Construction of Transportation Facilities

Click on any of the headings below to link to articles on that subject.

  1. Bridge Design and Performance
  2. Construction: General
  3. Construction: Pavements
  4. Construction: Structures
  5. Bituminous Materials
  6. Cement and Concrete
  7. Mineral Aggregates
  8. Pavement Management, Design and Performance
  9. Roadside Safety
  10. Soils, Geology and Foundations

Do you have suggestions or comments about/ this catalog? Write us: mailto:fejl@nas.edu

991118 "Analysis of Paving Construction Quality for Urban Highway Weekend Closures"
Phillip S. Dunston, Bonnie M. Savage, and Fred L. Mannering

991497 "Evaluation of Rigid Pavement Joint Seal Movement"
Dennis A. Morian, Nadarajah Suthahar, and Shelley Stoffels

991442 "A Regression Model for Resilient Modulus of Subgrade Soils"
Louay N. Mohammad, Baoshan Huang, Anand Puppala, and Aaron Allen

I. BRIDGE DESIGN AND PERFORMANCE

990008 "Construction Of A Full-Scale Soundwall Using Recycled Plastic"

Abstract: A full-scale, recycled plastic soundwall is constructed and its structural behavior analyzed to determine the feasibility of using recycled plastics in place of conventional building materials. A design process that allows selection of recycled plastic support columns that limit lateral deflection of a prototype soundwall due to wind loading is introduced as are techniques that are used to fabricate and install components of the barrier. Analysis of the prototype structure includes monitoring of response to environmental factors such as exposure to ultraviolet radiation and testing of acoustic insertion loss. Conclusions: A modularized form of design was developed that allows construction of a soundwall that has a variety of modules. With exception of concrete footings, steel reinforcing bars inside plastic columns, and a modest number of metal connections, the barrier utilizes 100% recycled plastic products. Structurally, all modules in the prototype barrier have maintained their integrity over the course of approximately one year. An exception, mostly aesthetic, is the warping of some plastic sheet panels. In contrast, plastic lumber boards show no detrimental effects from weathering and exposure to ultraviolet radiation. Also, there is no noticeable deformation of the structure indicating that the internal framework is capable of withstanding long-term thermal loadings. Acoustically, insertion loss of the recycled plastic soundwall is exceptional giving a noise reduction of approximately 17 A-weighted decibels. This reduction far exceeds insertion loss for soundwalls specified by state transportation agencies. Given the adequate levels of performance, both structurally and acoustically, implementation of the proposed design for a recycled plastic soundwall is recommended.

Paul N. Roschke, Associate Professor, Department of Civil Engineering, Texas A&M University, College Station, TX 77843-3136, Telephone: (409) 845-1985, FAX: (409) 845-6554, Email: p-roschke@tamu.edu; and Steven T. Esche, Engineer-In-Training, J. Ray McDermott Engineering Houston, L.L.C., 801 N. Eldridge Street, Houston, TX 77079, Telephone: (281) 870-5000, FAX: (281) 870-5045, Email: steve.esche@mcdermott.com.

990028 "Quality Improvement Review of Jointless Bridges and Bridge Deck Joints in Washington State"

Abstract: This paper summarizes highlights of a 1997 Quality Improvement Review of jointless bridges and bridge deck joints in Washington State. The purpose of the QIR is to determine, assess, and disseminate the current state of the practice and to share this information with the other FHWA Region 10 states and other FHWA regions. The inspection team included personnel from FHWA, Oregon DOT (ODOT), and Washington DOT (WSDOT). Interviews were conducted with design, construction, inspection, and maintenance personnel. During the QIR, eighteen WSDOT bridges were inspected in the field to gauge the performance of jointless bridges and bridge deck joints. Background information on jointless bridges is given and current bridge deck joint practices are presented. The use of jointless bridges eliminates the need for expansion joints and the need for joint maintenance. The QIR found WSDOT's semi-integral jointless bridges with overall lengths of 122 m and skews less than 30 degrees to have performed well. Approach slabs are recommended for jointless bridges to minimize the effects of approach settlement. Quality improvement recommendations are presented. WSDOT has developed a new sawcutting procedure for compression seals as well as a second generation fatigue-based modular bridge expansion joint specification to improve long-term durability. Conclusions: Joints: WSDOT should continue to have a full-time expansion joint specialist to serve as an expert and resource contact. New joints, design, and detailing require more time and understanding than can reasonably be expected of bridge designers. Provide education and training for WSDOT's construction inspectors and contractor's personnel. One education approach is to use videos to emphasize critical preparation and installation procedures to ensure high quality and a durable joint. Develop construction inspection guidelines on joint installation for the WSDOT Construction Manual. Proper joint installation appears to be the single most important factor in determining satisfactory long-term performance of joints. Consider using warranties for joints to improve quality during installation. Warranties were used on two contracts. The use of warranties may be beneficial to obtain a quality installation. Reconsider the use of steel finger joints and sliding plate expansion joints. Although WSDOT's current policy is to provide a sealed deck system for environmental reasons, these older joint systems have a good overall performance history. Maintenance personnel and bridge inspection personnel favor their use. The minimal damage caused by joint leakage may be offset by their simple design and good performance. Invite WSDOT construction project personnel to the annual WSDOT bridge maintenance meetings and encourage bridge maintenance personnel to attend yearly construction conferences. The interviews suggest that both parties will benefit from this exchange of concerns, information, and ideas. These annual meetings can be very effective in transferring information to a wide range of users. Provide construction tolerances in specifications for preparing concrete surfaces and installation of expansion joints. This will enable both designers and construction personnel to use reasonable construction tolerances for joints. Continue to develop innovative methods for constructing reliable joints such as the sawcutting procedure for compression seals. Additional work still remains to refine this procedure into a standard method. However, this quality improvement process will help improve the long-term durability of compression seal joints. Place WSDOT's Qualified Products List on the WSDOT Internet home page as a resource to other state DOTs. Develop one day training seminars for FHWA Region 10 DOT joint specialists, construction inspectors, bridge inspectors, and maintenance personnel. This provides a networking opportunity to share lessons learned in improving the quality and durability of expansion joints.

Jointless Bridges: Encourage the use of jointless bridges. This review confirms that jointless bridges types are preferred to jointed designs for the short to medium span ranges. The maximum skew limit of thirty degrees seems an appropriate upper limit for skew angle. The semi-integral abutment detail is performing very well. The decision to install an approach slab should be made by the bridge designers after consultation with the Geotechnical Branch. This decision should be based upon long-term performance and life cycle costs, rather than initial first cost to the project. There was unanimous support from all disciplines for using approach slabs on jointless bridges.

John A. Van Lund, Bridge and Structures Office, Washington State Department of Transportation, Olympia, WA 98504-7340, Tel: 360-705-7217, Fax: 360-705-6814, Email: VanLunJ@wsdot.wa.gov.us; Barry B. Brecto, Region10 FHWA - Washington, 711 South Capitol Way, Suite 501, Olympia, WA 98501-0943, Tel: 360-753-9482, Fax: 360-753-9889, Email:

Barry.Brecto@fhwa.dot.gov.us.

990065 "Bending Tests of Bridge Deck Planks"

Abstract: This paper presents results of timber plank tests, for planks used in highway bridge decks. They are oriented and loaded flat-wise. Tests were carried out to determine the flat-wise use factor, which is represented by the ratio of modulus of rupture (MOR) for flat-wise loading to MOR for edge-wise loading. The tests were carried out at the University of Michigan on the most common species used for plank decks in Michigan, Red Pine. Four sizes were tested, two are typical for bridge planks: 100x250mm (4"x10") and 100x300mm (4"x12"), and the other two sizes have good potential for future applications: 100x150mm (4"x6") and 100x200mm (4"x8"). A total of 169 edge-wise and 177 flat-wise specimens were tested. The resulting MOR's are presented in the form of cumulative distribution functions on normal probability paper. For comparison, MOR values were calculated, using actual dimensions and dressed sizes. The tests confirmed that MOR for flat-wise loading is considerably larger than for edge-wise loading for the larger planks tested and that flat-wise use factor increases for larger plank width. The flat-wise use factor in the current bridge design code is overly conservative for typical plank sizes. Conclusions: The wood plank tests performed at the University of Michigan confirmed that the modulus of rupture (MOR) for flat-wise loading is considerably larger than for edge-wise loading for the larger plank sizes tested. Flat-wise use factor increases for larger plank width. The flat-wise use factor in the current bridge design codes is overly conservative, for typical bridge plank sizes. New flat-wise use factors are recommended for the design of wood plank decks for highway bridges. The recommended values vary from 1.10 for 100x150mm (4"x6") to 1.6 for 100x300mm (4"x12").

Andrzej S. Nowak, Department of Civil and Environmental Engineering, 2370 G.G. Brown Building, University of Michigan, Ann Arbor, MI 48109-2125, tel. (734) 764-9299, fax (734) 764-4292; Pawel Stankiewicz, ADAPT Corp., Redwood City, CA 94061, tel. (650) 306-2400, fax (650) 364-4678; and Michael A. Ritter, Forest Products Lab, Madison, WI 53705, tel. (608) 231-9229, fax (608) 231-9303.

990133 "Simplified Method for Shear Design of Prestressed Concrete Girders"

Abstract: The new AASHTO LRFD Bridge Design Specifications incorporate the modified compression field theory for shear design of prestressed and non-prestressed concrete members. This method is based on the variable-angle truss analogy model and takes into account the inclination of diagonal shear cracks, strain in longitudinal steel and the applied shear stress on a section. This is a realistic approach to predict the shear resistance of any section of a concrete member. However, for prestressed concrete sections, an iterative process is required to determine the shear resistance of the sections. In an effort to simplify the process, Washington State DOT has completed a parametric study, resulting in a simplified method using fixed shear design parameters for WSDOT standard girders. A detailed step by step shear design based on the current AASHTO LRFD Specifications and the simplified method is given. The simplified method saves significant time in shear design of prestressed girders, especially when it is applied to standardize the shear reinforcement in a series of standard prestressed concrete girders. Shear cracking is a complex problem because of the complexity factors that contribute to the cracking mechanism. Some of the controlling factors are: the compressive and tensile strength of the concrete, the span to depth ratio of the member, the magnitudes of axial force, shear and moment at the section, the amount of shear and longitudinal reinforcement, and so on. Conclusions: The LRFD Specifications predict the shear resistance of prestressed girders more accurately than the LFD Specification and resulting in higher shear capacity of the sections. The LRFD requires less shear reinforcement in prestressed girders than LFD for the current WSDOT Standard prestressed girders. A simplified method using fixed shear design parameters of q and b may be utilized to simplify the LRFD shear design of prestressed girders. For the WSDOT Standard Prestressed Girders, q equal to 35 degrees and b equal to 2.4 are found to meet the shear design requirements of the LRFD. Similar fixed design parameters may be obtained for other sets of standard prestressed girders used by other states. The simplified method saves significant time in shear design of prestressed girders using the LRFD. Further time and cost savings may be realized by applying the simplified method of using fixed shear design parameters to standardize the shear reinforcement in a set of standard prestressed girders. The vertical components of harped or draped strands contribute as much as 10% of the total shear resistance of the section.

M. Myint Lwin, Bridge and Structures Office, Washington State Department of Transportation, Phone: (360) 705-7207, Fax: (360)705-6814, and Email: lwinm @wsdot.wa.gov; and Bijan Khaleghi, Bridge and Structures Office, Washington State Department of Transportation, Phone: (360) 705-7181, Fax: (360) 705-6814, and Email: khalegb@wsdot.wa.gov.

990266 "Simplified Method for LRFD Shear Design"

Abstract: Determination of the shear strength of prestressed concrete beams has become complicated in recent years. Much of the complexity comes from determining the concrete contribution, Vc, to the overall shear resistance. Because of the empirical nature of Vc calculation by various codes and specifications and because of the insignificant cost impact of shear reinforcement, the complexity is not warranted. A simplified shear design method is proposed. A detailed example is given to demonstrate design based on the current AASHTO LRFD Specifications and the proposed method. Another important issue in shear design of thin-web precast prestressed concrete members is the maximum allowed shear reinforcement. AASHTO Standard Specifications require that Vs not exceed (fc’ in MPa) (fc’ in psi). This limit has become a controlling design factor when wide beam spacing and high performance concrete are utilized. It is almost always a controlling parameter in the design of post-tensioned I-beams. Recent experiments have shown that: (1) This limit is too conservative; and (2) The limit of 0.25fc’bvdv on (Vc + Vs) in the AASHTO LRFD Specifications can be reached if adequate anchorage of the prestressing steel at member ends is provided. A summary of the full-scale test results is presented. Conclusion: In conclusion, the proposed simplified LRFD shear design method is a safe and simple method that does not require any iterative process as the current AASHTO LRFD does. There is no need for tables and charts. It is a more reasonable method in the sense that it predicts a uniform shear reinforcement pattern which follows the factored shear force diagram. It is simple to understand and to use in both simply supported bridge beams and continuous bridge beams. In comparison with our full-scale tests as well as other experimental data available in the literature, with proper reinforcement the maximum shear capacity of 0.25 fc’ bvdv can be easily reached. This limit represents a lower bound fit to the experimental results when the longitudinal reinforcement has enough anchorage as specified. The maximum shear reinforcement limit specified in AASHTO Standard Specifications is too restrictive.

Zhongguo (John) Ma, University of Nebraska-Lincoln, Engineering Building, Room # 129, 60th & Dodge Streets, Omaha, NE 68182, Tel: (402) 554 – 2820, Fax (402) 554 – 3288, Email: zma@unomaha.edu; Maher K. Tadros, University of Nebraska-Lincoln, Engineering Building, Room # 129, 60th & Dodge Streets, Omaha, NE 68182, Tel: (402) 554 – 2985, Fax (402) 554 – 3288, Email: mtadros@unomaha.edu.

990331 "Verification of Girder Distribution Factors for Short-Span Bridges by Field Testing"

Abstract: This paper presents the procedure and results of field tests that were performed on five simply supported short span steel girder bridges to verify girder distribution factors. Prior analytical studies have shown that in most cases currently used girder distribution factors are too conservative. However, these studies also showed that for short spans and short girder spacings, the girder distribution factors can be too permissive. Therefore, this paper focused on experimental evaluation of girder distribution factors for short span steel girder bridges. The research work involved formulation of the testing procedure, selection of structures, installation of equipment, measurements, and processing of the results. Strains and deflections are measured and filtered to calculate girder distribution factors. The results were compared with the distribution factors specified by AASHTO Standard (1996) and AASHTO LRFD Code (1994). It has been found that the measured girder distribution factors are lower than AASHTO values in all cases. Conclusions: Five short-span two lane bridges were tested. The field measurements confirmed that the actual (measured) girder distribution factors are smaller than those specified by AASHTO Standard (1996) and AASHTO LRFD Specifications (1994). For three bridges, the measured GDFs for two side-by-side 11-axle trucks were close to but less than S/3.36 (where S is in meters), and for two other bridges they were approximately S/5. FEM analyses provided GDFs close to S/3.36. For comparison, the GDF's obtained in field tests as a part of this study, are plotted versus analytical values calculated using AASHTO Specifications (1996), and AASHTO LRFD Code (1994). The results are presented for a single truck (one lane loaded), and for two trucks (two lanes loaded).

Andrzej S. Nowak, Junsik Eom and Ahmet Sanli, Department of Civil and Environmental Engineering, 2370 G.G. Brown Building, University of Michigan, Ann Arbor, MI 48109-2125, tel. (734) 764-9299, fax (734) 764-4292. Roger Till, Michigan Department of Transportation, P.O. Box 30049, Lansing, MI 48909, tel. (517) 322-5682, fax (517) 322-5664.

990411 "Subjective and Objective Evaluations of Bridge Damage"

Abstract: A decommissioned 40+ year old reinforced concrete deck on steel girder bridge was subjected to a series of induced damages, nondestructive field tests, and visual evaluations in order to compare objective and subjective methods of bridge condition assessment. Subjective evaluations of bridge condition produced highly variable results - inspectors with different backgrounds and field experience disagreed on how severely deterioration and damage influenced bridge behavior/safety and, consequently, generated different assessments of bridge condition. Furthermore, a load-rating of the as-is state of the bridge, e.g., the state prior to any induced damages, based on current Ohio DOT procedures indicated that the bridge could only support truck-loads of 227,804 N (51,192 lbf). However, for this particular bridge state and when subjected to truck-loads of 282,130 N (63,400 lbf), objective data acquired during nondestructive field testing revealed maximum superstructure deflections and live-load stresses of 0.190 cm (0.075 in.) and 15,985 kPa (2,320 psi), values well within AASHTO limits. These values also imply that the bridge can support loads much greater than those indicated in the load-rating. Comparing the subjective and objective assessments for the induced damage scenarios yielded results similar to those for the as-is bridge condition. Essentially, it was revealed that subjective bridge evaluation, unlike objective methods of condition assessment, was unable to properly characterize neither intrinsic bridge mechanisms nor the influence that such mechanisms have on bridge behavior. Condition assessment of typical reinforced concrete deck on steel girder bridges should therefore include objective evaluations of bridge condition and behavior. Conclusions: In-situ bridge mechanisms, such as flexibility, were successfully characterized from the objective data acquired through nondestructive field test methods such as dynamic impact testing and truck-load testing. Such data revealed that the decommissioned test-bridge could support service truck-loads - measured deflections and strains (stresses) were considerably less than AASHTO serviceability and stress requirements. However, the subjective results of an Ohio DOT inspection performed prior to any field research were used to decommission the bridge. This and other numerous subjective evaluations performed on the bridge during the course of this research apparently did not capture the true nature of intrinsic bridge mechanisms nor the influence that such mechanisms have on bridge behavior such as load distribution and structural flexibility. Using a 3-D field-calibrated finite element model to incorporate the objective characterizations of these mechanisms into the load-rating process consequently yielded ratings that indicated the bridge could support truck-loads greater than those predicted by current Ohio DOT load-rating procedures. Objective methods of bridge assessment, such as nondestructive field test methods, should therefore be included as part of the condition assessment process.

Michael S. Lenett, University of Cincinnati, Dept. of Civil and Environmental Engineering, 741 Baldwin Hall, Mail Location #71, Cincinnati, Ohio 45221-0071, email: lenettms@email.uc.edu, phone: 513-556-3687 or 513-556-3679, fax: 513-556-2599.

990430 "Steel Orthotropic Decks - Developments in the 1990's"

Abstract: Paper summarizes recent developments in the field of orthotropic decks which are indispensable in the design of very long span bridges. European research results and recommendations are discussed. Fatigue susceptibility of decks with closed ribs and thin deck plates is highlighted by catastrophic cracking of decks in Holland in 1997. The writer discusses the cause which is stress flow constriction in the deck plate not previously considered and proposes a solution for future designs. Open rib decks are less efficient but have much better fatigue resistance. Such decks are widely used on railway bridges in Europe. Surfacing failures are due to excessive deck flexibility. Conclusions: 1. In decks with closed ribs internal diaphragms at intersections with floorbeams eliminate stress concentrations in floorbeam webs and in the deck plate. V-shaped ribs are more efficient than traditional trapezoidal ribs. 2. Open-rib decks deserve more consideration in future designs. 3. Stresses in surfacing due to composite action with the deck must be considered and rib deflections minimized as required by AASHTO LRFD specifications. Thick surfacings are more vulnerable to effects of deck flexibility. Surfacings with low elastic modulus and little variability with temperature are desirable. 4. Practical design for fatigue should be based on semi-empirical rules for "distortion-induced" fatigue.

Roman Wolchuk, Consulting Engineers, 26 Journal Square, Jersey City, NJ 07306, Tel. 201 659-7428, Fax 201 659-6370, Email: wolchukeng@juno.com.

990485 "Steel Girder Bridge Field Test Procedures"

Abstract: Research has shown that in most cases, bridges exhibit capacities higher than analytical load capacity rating predictions. These rating procedures are based on conservative design assumptions that do not always represent the true bridge behavior. Testing bridges in the field has demonstrated this additional capacity and bridge field testing has become an acceptable means to determine a more accurate estimate of a bridge’s safe capacity. Many factors not considered in the design process contribute to the response of a tested bridge. Several of these, like the actual load distribution and additional system stiffness from curbs and railings, are welcome benefits and can be used to increase weight limits on bridges. However, there are also contributions from bearing restraint forces and unintended composite action that may not be reliable during the service life of the structure. Determining how much of the increase in capacity is acceptable is difficult. This paper presents systematic field test rating procedures that separates and quantifies these contributing factors so that owners may remove unwanted contributors and retain the reliable benefits. An efficient test plan is applied to a three-span steel girder bridge to demonstrate the procedures. Conclusions: Field testing provides the engineer with valuable knowledge of system response, load distribution, actual section properties, bearing restraint effects, and dynamic impact for the tested bridge. The standardize field testing procedures were developed from a series of diagnostic tests on the steel girder bridge to separate and quantify the factors tending to increase the load to (1) remove the unwanted contributions and (2) confirm the origin of the useable benefit. The results indicate that the current analytical single unit weight limit can be increased 67% after removing the questionable benefits from bearing restraint forces. The rating equation procedures presented have been optimized for time effort and cost.

Michael G. Barker, University of Missouri – Columbia, E2509 Engineering Building East, Columbia, Missouri, 65211, Tel: (573) 882-2467, Fax: (573) 882-4784, email: barkerm@missouri.edu.

990757 "Design Of An 11-Span Isolated Steel Structure For Serviceability, Puente Sobre El Rio Tempisque"

Abstract: The purpose of this paper is to discuss the design process and studies that were required to develop the design for the bridge across the Tempisque River in Costa Rica that would be serviceable under various seismic loads. Required levels of performance for various bridge components will be discussed. Costa Rica is located on the Caribbean tectonic plate - a very seismically active area that is currently in the midst of an intensive seismic cycle which began in 1982. The western coast is in a region of subduction between the Caribbean, the Cocos, and the Nazca Plates. The Tempisque River separates the resort laden western shores of Costa Rica from the country’s capital, San Jose, and the rest of the country east of the river to the Caribbean Ocean. While the country has relatively modest economic resources, a design must be developed that for this important transportation link that: meets the country’s stringent seismic design criteria; is relatively inexpensive; and, has a high potential of re-use following an earthquake. The bridge will be built and operated by the contractor. While this process reduces the initial costs for the owner, it can have implications on the required level of performance during the concession portion of the structure’s useful life. This will also be discussed. Conclusion: A design for a steel bridge that meets a "serviceable" performance criteria is discussed. Specific performance criterion for the structural components are defined. A strategy for achieving the serviceable design is elaborated on. Central issues to the serviceable design for a steel bridge are proposed to be; limiting the inertial loads in both the superstructure and substructure through the use of isolation bearing devices, tuning the structure through variation of substructure and bearing design, and addressing the performance requirements of the expansion joints. The reduced risk to the contractor during construction is shown, for this location, to be essentially defined by the same seismic event as the Design Earthquake. This implies that no additional analysis (other than for temporary works) is required by the designers to address the reduced risk during the construction and concession period. The design follows the philosophy that seismic design is not an exact science, that a bounded performance based design defines risks more clearly, and that a clear definition of risk is a strong foundation for any design.

Thomas R. Cooper, P.E., Senior Supervising Engineer, Parsons Brinckerhoff Quade & Douglas, Inc., 3840 Rosin Court, Suite 200, Sacramento, CA 95834, 916-567-2522, Fax: 916-925-3517, email: cooper@pbworld.com; and Cristoforo D. Subrizi, P.E, Lead Engineer, PBQ&D, Inc., Marathon Plaza, 303 Second Street, San Francisco, CA 94107, 415-243-4718, Fax: 415-243-9501, email: subrizi@pbworld.com.

990797 "Forced Vibration Testing of A Full Scale Bridge Span"

Abstract: A nine-span three-lane freeway overpass structure was demolished leaving an isolated single span supported by two bents. These concrete bents were subjected to lateral load capacity testing and retrofitting using carbon fiber composite wrapping. This testing provided the opportunity to perform forced vibration dynamic testing between each episode of damage or retrofit. This sequence resulted in a series of seven dynamic tests performed on the same structure in seven different conditions of damage or retrofit. This work focused on horizontal forced vibration utilizing an eccentric mass shaking machine. Frequency sweeps were conducted in each orthogonal horizontal direction. Data was collected with an array of accelerometers. This paper presents the natural frequencies determined for the structure at each of the seven damage states as well as some mode shape data. The natural frequencies correspond to the first three mode shapes for the structure, namely, the two translational modes and a torsional mode. Significant decreases in the natural frequencies occurred in the structure. Since the mass of the structure remained essentially constant throughout the testing, these decreases can be attributed to a significant lowering of the structural stiffness. A slight increase in structural stiffness occurred as a result of the carbon fiber retrofit and bridge repair. Changes in both the amplitude as well as the shapes of the modes were noted in the experimental results. Conclusions: Significant change occurred in the natural frequencies in the seven structural conditions. The substantial changes in the natural frequencies correspond to substantial changes in the structural stiffness. Loss of stiffness (decrease in natural frequencies) is demonstrated as a result of damage to the structure. The natural frequencies changed by 38%, 49%, and 52% for the fundamental, second, and third modes respectively. The inflicted damages and repairs at specific locations on the structure result in larger response for the same loading levels because of structural softening. Changes in mode shapes are currently being investigated and compared with analytical models. The use of epoxy crack repair and the application of carbon fiber composites at columns and beams result in detectable increases in structural stiffness.

Ikhsan Muhammad, Marvin W. Halling, and Kevin C. Womack, Department of Civil and Environmental Engineering, Utah State University, Logan, Utah 84322-4110, Tel. (435)797-3179, Fax. (435)797-1185, Email: halling@lab.cee.usu.edu.

990822 "Comparison of Experimental and Analytical Load Rating Methodologies for a Pony-Truss Bridge"

Abstract: Due to the limited resources of county and district bridge owners, the evaluation and rating of aging structures must be conducted to facilitate suitable bridge maintenance, repair, replacement, and posting strategies. The present study evaluates the effect of increasingly refining rating evaluation parameter inputs to the analysis of a 1937 riveted pony-truss bridge in Pennsylvania. The study considers results of experimental field testing of the bridge, a detailed section loss inspection, and refined analytical modeling using STAAD III to increase the accuracy of the rating analysis. Where a rating indicates an under-capacity, increasing the refinement of the analysis, or even an experimental evaluation of several parameters, may be justified. The present study evaluates the relative effect of utilizing: (1) allowable stress vs. load factor design methodologies; (2) experimentally derived vs. code specified impact and distribution factors; (3) experimental stress measurements vs. manual and computer stress calculations, and (4) member fixity and composite action for both inventory and operating rating with an AASHTO HS20-44 and ML-80 rating vehicle. Results are presented for selected truss members, floor beams, and stringers. Conclusions: The study found that the rating increases with each increasingly refined parameter input of dynamic load allowance, distribution factor, and refined analytical evaluation, with the rating factor increasing as much as 60% over a standard manual rating analysis by utilizing an experimentally based rating analysis. The best analytical computer model agreement with experimental results was obtained using a reduced deck stiffness to model deck deterioration, fully composite action between stringers and deck, pinned stringer-floor-beam connections, and fixed floor beam to truss connections. The procedures described here-in can be generalized and applied to other similar bridge structures.

Timothy S. Schenck, Structural Engineer, HLW International, LLP, 115 5th Ave, New York, NY 10003, Email: tschenck@hlw.com, Tel: (212) 353-4870, Fax: (212) 353-4896; Jeffrey A. Laman, Ph.D., P.E., Assistant Professor of Civil Engineering, Department of Civil and Environmental Engineering, Pennsylvania State University, University Park, PA 16802, Email: jlaman@psu.edu, Tel: (814) 863-0523, Fax: (814) 863-7304; Thomas E. Boothby, Ph.D., P.E., Associate Professor of Architectural Engineering, Department of Architectural Engineering, Pennsylvania State University, University Park, PA 16802, Email: tebarc@engr.psu.edu, Tel: (814) 863-0523, Fax: (814) 863-4789.

990888 "Transverse Cracking in Bridge Decks"

Abstract: The purpose of this study was to determine the dominant parameters that lead to premature transverse cracking in bridge decks and to make recommendations expected to reduce cracking tendency in bridge decks. The project was divided into two main parts: a field study and a parametric study. The objective of the field study was to determine the correlation between the observed cracking and available design, material and construction-related data. Seventy-two bridges located in the Minneapolis-St. Paul area were included in the field study. The objective of the parametric study was to investigate the relative influence of the factors that affect transverse deck cracking through a controlled analytical study. The variables included: end restraint, girder stiffness, shrinkage, supplemental steel bar cutoff, cross frames, splices, deck concrete modulus of elasticity, and temperature history. In addition, four bridges from the companion field study were modeled using the available design, material and construction information to correlate the analytical results with the actual crack patterns. Conclusions: Based on the results of the study and correlation with other research, the following dominant factors affecting transverse cracking were identified: longitudinal restraint, deck thickness, top transverse bar size, cement content, aggregate type and quantity, air content, and ambient air temperature at deck placement. Concrete decks on prestressed girder bridges never cracked in the parametric study and rarely cracked in the field study. The factors that had the greatest influence on the steel bridge deck cracking were end restraint and deck shrinkage. Recommended practical improvements to bridge deck construction include: reducing the shrinkage of the deck concrete through mix design and/or better curing practices, and minimizing continuity over interior supports.

Catherine French, P.E., Professor and Associate Head, Dept. of Civil Engrg., University of Minnesota, 500 Pillsbury Drive S.E., Minneapolis, MN 55455-0220. Phone: (612) 625-3877, Fax: (612) 626-7750, Email: cfrench@tc.umn.edu; Laurice Eppers, TT-CBM Engineers, 5 N. Wabash Ave., Chicago, IL 60602. Phone: (312) 346-0190, Fax (312) 346-0638, Email: Leppers@tt-cbm.com; Quoc Le, Opus Engineers, Minneapolis, MN. Phone: (612) 934-4608, Email: Lexx0051@tc.umn.edu; and Jerome Hajjar, Associate Professor, Dept. of Civil Engrg., University of Minnesota, 500 Pillsbury Drive S.E., Minneapolis, MN 55455-0220. Phone: (612) 626-8225, Fax: (612) 626-7750, Email: hajja001@tc.umn.edu.

990935 "Why AASHTO LRFD"

Abstract: The AASHTO LRFD is based on new development in bridge engineering, sound principles and logical approach to assure constructability, safety, serviceability, inspectability, economy and aesthetics. It incorporates the best of Working Stress Design (WSD) and Load Factor Design (LFD), which are familiar to practicing bridge engineers. It is a comprehensive, well organized, and practical specification with commentary to provide explanation and background information. New bridges designed in accordance with LRFD has the inherent advantage of a more uniform level of safety, resulting in low life-cycle cost. LRFD allows the use of advanced methods in design and analysis. It provides flexibility for maintaining good and successful engineering practices or customizing load and resistance factors to meet the demands of a project. There are many good reasons and motivations to use LRFD. College classes, training courses, design examples, workshops and computer softwares are now available to ease the implementation of AASHTO LRFD. Conclusions: The new AASHTO LRFD Bridge Design Specification is the result of continuous improvement since AASHTO adopted the first national bridge code in 1931. The code had changed from Working Stress Design (WSD) in 1931 to Load Factory Design in 1975 and now to the Load and Resistance Factor Design (LRFD). LRFD is a modern and comprehensive bridge specification, which puts U.S. practice at the leading edge of bridge engineering. The AASHTO LRFD is based on technological advances in bridge engineering, sound scientific principles and systematic approach to ensure constructability, safety, serviceability, inspectability, economy and aesthetics. The AASHTO LRFD has the inherent advantage of a more uniform level of safety in new bridges, which means low maintenance and repair and low life-cycle cost. The parallel commentary in the AASHTO LRFD helps the bridge engineers in understanding the rationale and background of the specifications. It takes the "black box" out of the specification requirements. The AASHTO LRFD fulfills the vision to design and build quality bridges for the 21st Century.

Myint Lwin, Washington State Department of Transportation, P.O. Box 47340, Olympia, WA 98504-7340, Phone: 360-705-7207, Fax: 360-705-6814, Email: lwinm@wsdot.wa.gov.

990940 "Field Performance of Integral Abutment Bridges in Tennessee"

Abstract: The use of integral abutments in highway bridges is not new; the pioneering efforts of bridge designers in California, Ohio, Oregon, and South Dakota have demonstrated the efficacy of this design approach because of the elimination of troublesome joints. While not a "pioneer" in the sense of being the first, the Tennessee Department of Transportation (TDOT) has extended the use of integral abutments to longer and longer spans and is currently the national leader in applying this design concept. This paper consists of two sections: (1) current practice and related field experience and (2) research in progress. Consistent with these two sections, the paper has two objectives: (1) to provide specific examples of TDOT’s experience with integral abutment bridges and (2) to describe research designed to investigate the behavior of integral abutments and to provide some preliminary test results. The longest bridges in Tennessee to incorporate integral abutments are recently built bridges of 1,150 feet (350 m) in concrete and 525 feet (160 m) in steel. While these bridges are still too young to provide definitive information regarding potential problems, the current status of the bridges is described in the paper and details of the abutments are given. Experience with other, older bridges are discussed Field tests are currently in progress at The University of Tennessee, Knoxville, to study the effects of lateral movement due to temperature change on the behavior of an integral abutment. Lateral pile displacements of greater than one inch (25 mm) have been introduced with essentially no damage to the concrete abutment. Conclusions: The paper presents the results of a visual inspection of a number of integral abutment bridges in Tennessee and preliminary results of a field research project which is ongoing. The primary conclusion from the visual inspection of bridges in service was that deck cracking is no more of a problem in integral abutment bridges than in other continuous bridges. The trend in Tennessee toward longer jointless bridges has led to no significant problems. The results of the field research also support the trend to longer jointless bridges. Cracking of the test abutments under large lateral displacements has not compromised the structural integrity of the pile - abutment interface.

Edwin G. Burdette, Professor of Civil Engineering, The University of Tennessee, Knoxville, TN 37996, Tel: (423) 974-7704, Fax: (423) 974-2669, Email: eburdett@utk.edu; Edward P. Wasserman, Director of Structures Division, Tennessee Department of Transportation, Nashville, TN 37243-0339, Tel: (615) 741-3351; David W. Goodpasture and J. Harold Deatherage, Professors of Civil Engineering, The University of Tennessee, Knoxville, TN 37996, Tel: (423) 974-7703 and 974-0724, Fax: (423) 974-2669, Email: David-Goodpasture@utk.edu and hdeath@utk.edu.

991027 "Railing Systems for Use on Timber Deck Bridges"

Abstract: Bridge railing systems in the United States have historically been designed based on static load criteria given in the American Association of State Highway and Transportation Officials (AASHTO) Standard Specifications for Highway Bridges. In the past decade, full-scale vehicle crash testing has been recognized as a more appropriate and reliable method of evaluating bridge railing acceptability. In 1989, AASHTO published the Guide Specifications for Bridge Railings which give the recommendations and procedures to evaluate bridge rails by full-scale vehicle crash testing. In 1993, the National Cooperative Highway Research Program (NCHRP) published Report 350, Recommended Procedures for the Safety Performance Evaluation of Highway Features, which provides criteria for evaluating longitudinal barriers. Based on these specifications, a cooperative research program was initiated between the University of Nebraska-Lincoln and the Forest Products Laboratory, and later the Federal Highway Administration, to develop and crash test eleven bridge rails for wood deck bridges. This paper describes the research that resulted in the successful development and testing of eleven bridge railing systems for longitudinally- and transversely-laminated wood bridge decks in accordance with the AASHTO Performance Level 1 and 2 (PL-1 and PL-2) requirements, and the Test Levels 1, 2, and 4 (TL-1, TL-2, and TL-4) requirements of NCHRP Report 350. Conclusions: This program clearly demonstrates that crashworthy railing systems are feasible for both longitudinal and transverse wood decks. Even at high-impact conditions required by AASHTO PL-2 and NCHRP 350 TL-4, the railing systems performed well with no significant damage to the bridge superstructure. With the development of crashworthy railing systems, a significant barrier to the use of longitudinal and transverse wood deck bridges has been overcome. At the onset of this research program, only one crash tested bridge railing was available for use on wood deck bridges. Over the last ten years, this cooperative research program has resulted in the development of eleven crash tested bridge rails for use on both longitudinally- and transversely-laminated timber deck bridges.

Ronald Faller, Midwest Roadside Safety Facility, University of Nebraska-Lincoln,1901 Y St., Building C, Lincoln, Nebraska 68588-0601, Phone: (402) 472-6864, Fax: (402) 472-0506, Email: rfaller@unlinfo.unl.edu; Barry Rosson, Civil Engineering Department, University of Nebraska-Lincoln, W348 Nebraska Hall, Lincoln, Nebraska 68588-0531, Phone: (402) 472-8773, Fax: (402) 472-8934, Email: brosson@unlinfo.unl.edu; Michael Ritter, Forest Products Laboratory, USDA - Forest Service, One Gifford Pinchot Drive, Madison, Wisconsin 53705, Phone: (608) 231-9229, Fax: (608) 231-9303, Email: mritter@facstaff.wisc.edu; Sheila Duwadi, Turner-Fairbank Highway Research Center, Federal Highway Administration, 6300 Georgetown Pike, McLean, Virginia 22101-2296, Phone: (703) 285-2472, Fax: (703) 285-2766, Email: sheila.duwadi@fhwa.dot.gov.

991065 "Effects of Horizontal Web Reinforcement on Shear Capacity, Shear Ductility and Strand Anchorage"

Abstract: Simple truss models demonstrate that the inclusion of horizontal reinforcement can improve shear capacity in end regions of pretensioned girders where the prestressing strands may not be fully effective. The same truss models can demonstrate that the inclusion of horizontal reinforcement within the web could increase shear capacity within the web, and could limit propagation of shear cracking that occurs in the end regions of pretensioned girders. Previous experimental evidence has indicated that beam failures result when shear cracking propagates through the anchorage zones of pretensioned strands, thus destroying the capacity of the strands to develop the tensioned required to support shear forces. An experimental program was performed to investigate the effectiveness of horizontal shear reinforcement in improving shear capacity, improving shear ductility and preventing strand anchorage failures near end regions of pretensioned concrete bridge girders. Four pretensioned I-shaped girders were cast with varying shear reinforcement details in the end regions. The results of the experiments are studied and compared to the shear provisions in current ACI and LRFD bridge codes. The results from two of the beams are presented in this paper. Conclusions: Test results demonstrate that the inclusion of horizontal steel in the end regions of pretensioned concrete girders improved both shear capacity and shear ductility. In beam ends without horizontal steel, shear failure coupled with strand anchorage failure occurred almost immediately after the formation of the first web shear crack. Conversely, in the beam ends containing horizontal shear, web shear cracking was limited in size, strand anchorage was less affected and the beams were able to develop flexural capacity.

Bruce W. Russell, Assistant Professor, University of Oklahoma, 202 W. Boyd St., Norman, OK 73019, Tel:(405)325-1416, Fax:(405)325-6826; John Jacob, Graduate Research Assistant, University of Washington.

991191 "Proposed Revisions to AASHTO Standard Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals"

Abstract: The 1985 AASHTO Standard Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals has been revised in its entirety with significant additions made to its content and scope. The main objective of the study was to update the previous edition of the Supports Specifications. From a design safety standpoint, all materials for structural supports were treated on an equitable basis. While safety, aesthetics, and economy were three main guidelines in developing the provisions of the Supports Specifications, manufacturing practices and experiences were also taken into consideration. The purpose of this paper is to present highlights of the proposed revisions to the specification. The supporting information, scope, and basis for the proposed changes are also discussed. Conclusions: The proposed specification is the result of an extensive research study performed under NCHRP Project 17-10. Considerable effort was made to specify the best practice, realizing the characteristics and limitations of each material. The document is presented in a specification/commentary side-by-side format that will enable the engineer to review with ease the basis of specification’s provisions. References are updated to provide a resource for research studies related to the structural behavior and performance of structural supports. Overall, the proposed specification represents a vast improvement over the previous editions. It is hoped that the revised specification and the comprehensive information it contains would result in enhancing the design and use of structural supports for highway signs, luminaires, and traffic signals.

Fouad H. Fouad, Ph.D., P.E., Professor and Chairman, Department of Civil and Environmental Engineering, University of Alabama at Birmingham, 1075 13th Street South, Birmingham, AL, 35294, Phone: (205) 934-8430, Fax: (205) 934-9855, Email: ffouad@eng.uab.edu.

991238 "Fatigue Design of Modular Bridge Expansion Joints"

Abstract: The results of NCHRP Project 12-40, Fatigue Design of Modular Bridge Expansion Joints, are described in this paper. This research included experimental and analytical research to develop performance-based specifications and commentary for the fatigue design of modular bridge expansion joints (MBEJ). Field testing was conducted to measure static strain distribution and dynamic response of MBEJ subjected to truck loads. In addition, static load and strain distributions were also measured in the laboratory by applying loads through a truck axle and tires. The proposed fatigue design and test specifications are intended to be integrated with the present LRFD bridge design code. In order to be consistent with these bridge design specifications, the proposed MBEJ fatigue-design specifications used the same fatigue-design truck as the present AASHTO bridge specifications. One important modification of the AASHTO truck loading for MBEJ however, is the explicit recognition that the rear axles of the HS series trucks actually represent tandem axles. A simplified method to estimate the distribution factor, i.e. the fraction of the design wheel load range assigned to a single centerbeam, was recommended. Suggested fatigue test acceptance methods are also included. MBEJ designed in accordance with the proposed specifications should not be susceptible to fatigue cracking and will not cost significantly more than currently designed systems. Conclusions: The proposed specification provides an established fatigue design procedure and a procedure for carrying out the required fatigue tests. The proposed specifications are reasonably easy to use but are sophisticated enough to account for the complex dynamic behavior of the MBEJ as a system. In addition, the specifications are sufficiently general so that innovative new designs for MBEJ are not excluded from consideration. A higher level of confidence in long-term joint performance and possible decreased life-cycle costs will be realized.

Robert J. Connor, Graduate Research Assistant, ATLSS Engineering Research Center, Lehigh University, 117 ATLSS Drive, Bethlehem, PA, 18015; Tel: (610)758-6103 Fax: (610)758-5553 Email: rjc3@lehigh.edu; Robert J. Dexter, Associate Professor Civil Engineering, University of Minnesota, 122 CivE 500 Pillsbury Drive S.E. Minneapolis, MN 55455-0116, Tel: (612) 624-0063 Fax: (612) 626-7750 Email: dexter@tc.umn.edu

991370 "Long-Term Performance of Elastomeric Bridge Bearings"

Abstract: This report summarizes effects of long-term service on steel laminated elastomeric bearings placed on twin structures carrying the Aurora Expressway (New York State Route 400) over Conrail and NY 16, Erie County. Expansion-joint bearings replaced as part of rehabilitation project on these bridges were recovered for evaluation. Generally, the bearings were found to be in good condition, with only a few test values out of specification. NYSDOT's current accelerated-test procedures were were evaluated by comparing mean ratings of 1969 acceptance testing for these bearings after simulated aging, with results of the same tests in 1996 on the as-received samples after their removal from thses bridges. The Materials Bureau's acceptance tests (as used for the recovered samples) were validated by the comparison with results for the original, artifically aged bearings in 1969. Lastly, acceptance tests were done on the recovered bearings to evaluate performance on current specification tests. Included in this study is an analysis of mean ratings of acceptance test results from 1969 compared to mean ratings of the same tests to judge the effect of the years in service. The bearings used in the project had problems in design, construction, and materials properties, yet performed very well in service and are relatively insensitive to deficiencies in these areas. Conclusions: Neoprene's resistance to shear, weather aging, and compression set ensures a long service life and no maintenance in bridge bearing applications. This is borne out by the performance of the bearings on acceptance tests after 22 years' service. The value of NYSDOT's rigorous material specification and aging-test process of elastomeric properties is verified by the bearings' performance in the testing after service compared to initial aged-test results. The initial compressive deflection the bearings were subjected to, and subsequent performance, reinforces the need for proper design of the bearing (shape factor) to maintain effective rubber thickness to deflect shear stresses, as well as properly specified material properties.

Michael E. Doody, New York State Department of Transportation, 84 Holland Ave., Albany, NY 12208, Tel:(518) 474-6377 Fax: (518) 474-9963.

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II. CONSTRUCTION: GENERAL

990072 "Analysis of the Impacts of Freeway Re-Construction Closures in Urban Areas"

Abstract: The intent of this paper is to evaluate the traffic- and business-related impacts of a weekend closure of a major urban freeway. Data were gathered from a 9-km section of Interstate 405 (I-405) in Seattle that was closed to traffic in a single direction for two consecutive weekends, August 15-17 and August 22-24, 1997 for repaving operations. In evaluating this approach to highway reconstruction (i.e., total directional closure), we estimate the impact on the vehicle travel time and total emissions including carbon monoxide, oxides of nitrogen, and volatile organic compounds. Also, a survey was conducted asking travelers how their travel patterns changed in response to the weekend closure of this section of I-405. In addition to asking questions about changes in travel patterns, questions relating to the traveler's overall impressions were asked. Limited dependent analysis techniques including ordered probit and binary logit models were used in the survey analyses. Finally, a small sample of businesses was interviewed to get a quick sense of their impressions of the closure. Conclusions: The findings show that the impacts of total directional weekend closures are not excessive. From a traffic impact perspective, computer-generated simulations suggest travel-time impacts for the Seattle closure to be on the order of an 11-13% increase in system-wide travel time, which is quite reasonable when compared to other closure options (i.e., partial closure). The user survey indicated that only 12.7% of the users surveyed thought the closure had a major impact on their travel plans and 88.7% indicated a preference for total closures over partial closures. The statistical analyses showed that socioeconomics and geographic location affected the extent to which individual users were impacted but that few consistently adverse impacts were detected. The survey of local businesses also indicated only minor impacts.

Doohee Nam, Jinsun Lee, Phillip Dunston and Fred Mannering, Department of Civil and Environmental Engineering, University of Washington, Box 352700, Seattle, WA 98195-2700, Tel: (206) 517-3139, Fax: (206) 543-8935, Email: flm@u.washington.edu.

990516 "Current Use of Warranties in Highway Construction"

Abstract: The transportation industry is investigating non-traditional and innovative contracting practices that can lead to improvement in the areas of quality, safety, and the reduction of State Highway Agency (SHA) resources. Warranty contracting, best value, and A+B+I/D are some examples of the non-traditional and innovative practices currently being investigated by the highway construction industry. Warranty contracting has several advantages, including potential for reduced delivery costs, lower total construction costs, focus on performance outcomes rather then material outputs, improved quality, and an opportunity to provide SHAs with another contracting option. This paper reviews the history of warranty contracting in the United States, offers an assessment of the current status of SHA warranty contracting, presents issues to consider in drafting a model specification, and develops a framework for implementation of warranty contracting. Conclusions: Despite its advantages, warranty contracting is not appropriate for all situations. Therefore, an in-depth study should be conducted to determine what project, SHA, and contractor characteristics are necessary to have a successful warranty project. Data must also be collected and analyzed on on-going and future projects in order to determine the best practices regarding warranty contracting. SHAs will continue to increase the number of projects warranted and length of the warranty, tighten thresholds on performance indicators, and warrant more end products. Cooperation is very important in the development of a warranty program. The goals, risks and new responsibilities of all the parties involved need to be clearly defined and understood. With open communication between the SHA, the contracting community, and the surety companies, the warranty program can be successful.

Jeffrey S. Russell, Assoc. Professor, University of Wisconsin- Madison, Department of Civil and Environmental Engineering Room 2304 1415 Engineering Dr. Madison, WI 53706 Phone: 608-262-7244, Fax: 608-262-5199, russell@engr.wisc.edu; Awad S. Hanna, Assoc. Professor, University of Wisconsin- Madison, Department of Civil and Environmental Engineering Room 2260 1415 Engineering Dr. Madison, WI 53706 Phone: 608-262-0614, Fax: 608-262-5199, ashanna@facstaff.wisc.edu; Stuart D. Anderson, Assoc. Professor, Texas A&M University, Department of Civil Engineering CE/TTI Building Spence Street College Station, TX 77843-3136 Phone: 409-845-4414, Fax: 409-845-6554, sda4823@acs.tamu.edu; Patrick W. Wiseley, Project Engineer, EMCS Design Group, 205 W. Highland Ave. #501, Milwaukee, WI 53201 Phone: 414-347-1617; and Robert J. Smith, Attorney, Wickwire Gavin, Suite 300, 2 East Gilman St. P.O. Box 1683, Madison, WI 53701-1683 Phone: 608-257-5335, Fax: 608-257-2029, rsmith@wi.wickwire.com.

990579 "Use of Best Value Selection"

Abstract: Carter and Burgess, Inc., was selected by the Utah Department of Transportation (UDOT) to evaluate several aspects of the I-15 Design/Build Reconstruction project under construction in Salt Lake City. The evaluations are being completed in part to fulfill commitments made to the Federal Highway Administration as they granted a Special Experimental Project 14 (SEP-14) status to the I-15 project permitting design/build contracting methods. This report presents information about the selection process used by UDOT to hire a design/build team to work on this project. UDOT decided to use a "best value" selection process rather than low cost to select a contractor. The report discusses comparison between design-bid-build and design/build processes. It describes the "best value" selection process used by UDOT to evaluate and select a contractor, using the detailed selection process. A description of the organizational structure required to prepare and review the proposals is presented. Unique features of the UDOT process are discussed, including use of stipend, risk sharing, ISO 9000 certification, design life, performance specifications, "best and final offer" (BAFO), award fees and use of CD-ROM’s used to distribute the proposal information. Lessons learned in the process are also presented.

Stanley S. Postma, Carter & Burgess, Inc., 420 E. South Temple, Suite 345, Salt Lake City, UT 84040, email: postmass@c-b.com; Frank Carlisle, Carter & Burgess, Inc., 420 E. South Temple, Suite 345, Salt Lake City, UT 84040; James E. Roberts, CALTRANS, 1801 30th Street, 5th Floor, P.O. Box 942874, Bin #9, Sacramento, CA 94274, Tel: 916-227-8808, Fax: 916-227-8251, email: jroberts@trmx2.dot.ca.gov; and David Downs, Utah Department of Transportation.

991403 "In-House versus Consultant Design Costs in State Departments of Transportation"

Abstract: The use of consultants in providing pre-construction engineering designs services for state Department’s of Transportation has increased over the last 20 years. This has resulted in several investigations into the cost-effectiveness of this trend. This paper reviews past studies, examines their methodology, suggests improvements to certain parts of the commonly-used investigative process, and demonstrates their use in an application to the Louisiana Department of Transportation and Development. The suggested improvements include using the same project to compare in-house and consultant design costs (rather than the use of similar projects, as in most studies), performing a detailed analysis of overhead rates that are comparable between state and consultants, and measuring comparative design costs as the ratio of in-house to consultant design costs rather than as the ratio of design to construction cost commonly used in past studies. Conclusions: Most studies in the past have concluded that consultant design costs are higher than in-house costs or that there is not a significant difference in cost between the two. The Louisiana study found that consultants are approximately 20 percent more expensive than in-house staff in producing road and bridge designs but that the difference was almost entirely due to the extra cost of contract preparation and in-house supervision required for consultant designs. The study also identified factors other than cost that are used in decision-making to employ consultants.

Chester G. Wilmot, Department of Civil and Environmental Engineering, Louisiana State University, Baton Rouge, Louisiana 70803, Tel: (225) 388 4697 Fax: (225) 388 8652 Email:

cewilm@eng.lsu.edu.

Donald R. Deis, Department of Accounting, E.J. Ourso School of Business, Louisiana State University, Baton Rouge, Louisiana 70803, Tel: (225) 388 6214 Fax: (225) 388 5256 Email:

acdeis@unix1.sncc.lsu.edu.

Helmut Schneider, Director, Information Services and Decision Sciences, E.J. Ourso School of Business, Louisiana State University, Baton Rouge, Louisiana 70803, Tel: (225) 388 2126 Fax: (225) 388 2511 Email:

hschnei@lsu.edu.

Charles H. Coates, Jr., Consulting Civil Engineer, 2730 Tall Timbers Road, Baton Rouge, Louisiana 70816, Tel: (225) 292 8337.

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III. CONSTRUCTION: PAVEMENTS

990031 "The Development Of Smoothness Specifications For Flexible Pavements In The State Of Florida"

Abstract: Initial pavement smoothness has been shown to improve the overall pavement performance. This combined with the importance of providing a comfortable ride for the driving public justifies the importance of achieving high initial pavement smoothness. FDOT has recently developed smoothness specifications for asphalt pavements. These smoothness specifications will be used on high-speed facilities and they will be based on measurements obtained with laser road profilers. The ultimate goal is to include incentive/disincentive specifications aimed at rewarding the contractor for a high quality ride and simultaneously providing a financial deterrent to providing a poor quality ride. Conclusions: Ride Numbers measured with a laser profiler can be used to rank the level of rideability on rural projects with some limitations. The sections evaluated should be at least 0.100 mile in length. Roadway sections at bridges, railroad crossings, intersections, etc. will need to be tested using a rolling straightedge. Acceleration and deceleration lanes will also need to be tested with a rolling straightedge. Limitations that affect the use of the laser profiler for collecting ride data are stop and go driving due to traffic lights, traffic flow, etc. The laser profiler must operate at fairly constant speeds above 15 miles per hour. The laser profiler also must be operated at constant speed when it enters and leaves the test section. About twenty five percent of the new sections tested will have ride numbers less than 4.30. These sections are targeted for improvement with the newly developed specifications.

Khaled Ksaibati, University of Wyoming, PO Box 3295, Laramie, WY 82071-3295, 307-766-6230, Fax: 307-766-2221, khaled@uwyo.edu.

990229 "Summary of the 1996 PCC Performance-Related Specification Shadow Field Trial—Iowa State Route 23"

Abstract: This paper summarizes the results of a "shadow" field trial (actual contractor pay was not affected) conducted to demonstrate a "Level 1" prototype performance-related specification (PRS) for jointed plain concrete pavement (JPCP) construction. The Level 1 PRS (the most practical PRS method at this time) is believed to be immediately implementable because it uses currently practiced sampling and testing procedures. The future pavement performance is represented by distress indicators that are predicted based on measured quality characteristic (QAC) values. Pay factors are determined independently for each QAC from simulated pay factor vs. QAC curves and corresponding equations. The overall lot pay factor is determined from a simple mathematical manipulation of the individual QAC pay factors. The specific objectives of the field trial were to verify/confirm the draft specification's effectiveness, identify potential problem areas, and determine its reasonableness. This paper discusses all aspects of the field trial including the relevant definitions, selection of lots and sublots, sampling and testing plan, calculation of "shadow" PRS pay adjustments, problems encountered, and a summary of lessons learned. Conclusions: The successful completion of this first shadow field trial demonstrated that the current Level 1 PRS approach is both a reasonable and practical PRS method. It is believed that the current Level 1 PRS approach could be implemented by most State Highway Agencies (SHAs) with little change to an SHA's current QAC sampling and testing procedures. Valuable experience was obtained at the Iowa field trial, specifically in the area of developing practical QAC sampling and testing plans. The current PRS demonstration software (PaveSpec 2.0) was also revised to reflect the lessons learned at the Iowa field trial.

Todd Hoerner, and Michael Darter, ERES Consultants, Inc., 505 W. University Ave., Champaign, Illinois 61820, Tel: (217) 356-4500 Fax: (217) 356-3088. Email: thoerner@eresnet.com; mdarter@eresnet.com.

990230 "Nuclear Density Readings and Core Densities: A Comparative Study"

Abstract: This paper presents the findings of an investigation performed to identify possible correlations between nuclear density gauge readings and core density results. The nuclear density data was collected on a Superpave section of Interstate Highway I-95 in Brevard County. Core samples were also obtained from this section for laboratory density determination. Five gauge units (Troxler models 3401, 3440 (2 units), 3450, and 4640) and three core density methods (Florida test method FM 1-T 166, ASTM D 1188 using parafilm, and dimensional analysis) were considered. The relationships among the core density results were first analyzed. Then an investigation of the correlation among the different gauges used in this study was evaluated. Finally, the performance of each of the units with respect to the core density results was assessed. Conclusions: The findings of this study indicated that the five nuclear gauge density units did not always produce similar results and did not consistently correlate with the core densities. The nuclear density testing variability did not only differ from gauge to gauge but also from location to location within each gauge. In addition, a higher degree of correlation existed between core density methods than between the core and nuclear readings (an indication of a higher variability in nuclear density data as compared to that in core densities). The findings also suggest a need to correct the readings of all nuclear gauges, including the thin lift gauges, for the density of the underlying materials.

Bouzid Choubane, Patrick Upshaw, Gregory Sholar, Gale Page and James Musselman, Florida Dept. of Transportation, State Materials Office, 2006 N.E. Waldo Road, Gainesville, FL 32609, Tel: (352) 337-3100, Fax: (352) 334-1649, Email: bouzid.choubane@dot.state.fl.us.

990990 "Application Of Fiber Reinforced Concrete For Thin And Ultra-Thin Whitetopping On I-20 In Mississippi"

Abstract: A thin, portland cement concrete whitetopping project was constructed on Interstate 20 near Jackson, Mississippi in August 1997, as a test of this technology on a high traffic, high speed roadway. The primary objective of this project was to evaluate the potential of the 3M fibers to expand thin whitetopping (TW) applications to compete economically on routine roadways by extending slab length, since sawing and sealing joints is a significant part of the cost of constructing a TW. This project contained sections utilizing plain concrete, concrete containing 3M polyolefin fibers (50/63 fiber), and concrete containing fibrillated polypropylene fibers. Joint spacing for the 50/63 fiber section ranged from 1.82 m to 12.2 m. Joint spacings for the plain and fibrillated fiber sections were 3.65 m and 1.82 m, respectively. The whitetopping was done as an inlay in the truck lane of a hot mix asphalt pavement with a history of rutting despite 4 rehabilitations since 1983. Total project size was 1220 m long and 3.65 m wide and involved thicknesses of 100 mm, 150 mm, and 200 mm. This project involved partnering with industry and various branches of government. Monitoring data includes distress surveys, deflection surveys, and skid measurements. At 11 months of age, there are several corner cracks in the fibrillated fiber and 50/63 fiber sections. Some of the corner crack areas in the 50/63 section are deteriorating while those in the fibrillated fiber section appear stable. Conclusions: The plain and fibrillated fiber sections will perform well if proper sawing is done. It is obvious the 50/63 fiber sections, for all slab lengths, will require patching of many of the slab corners.

Alfred Crawley, Mississippi Department of Transportation, P. O. Box 1850, Jackson, MS 39215-1850, Tel: (601) 359-7650 Fax: (601) 359-7634, Email: acrawley@mdot.state.ms.us.

991118 "Analysis of Paving Construction Quality for Urban Highway Weekend Closures"

Abstract: This paper presents the results of an analysis of paving quality that was achieved through the implementation of a full weekend closure strategy for constructing an asphalt overlay. The pilot project was an approximately 8.87-km (5.5-mi) section of Interstate 405 (I-405) in Seattle that was closed to traffic in a single direction on two consecutive weekends, planned for August 15-18 and August 22-25, 1997, so that overlay construction could be performed. The Washington State Department of Transportation (WSDOT) used this approach as an alternative to frequent partial closures during nighttime hours. Quality parameters that were quantitatively examined for the mainline paving in this study were surface smoothness (rideability), in-place density, and gradation. Other factors such as the presence of "cyclic" segregation, the condition of longitudinal joints were assessed by observation. Since project-to-project comparisons are difficult to validate, the primary question of the analysis was whether consistent quality could be achieved between the night and day cycles of the paving operations. Comparisons with historical data were used to establish benchmarks for assessing quality in the general sense. The major findings were that consistent quality through the night and day cycles may be achieved with the weekend closure strategy, and the level of quality achieved on this project exceeds average reported quality levels in the parameters examined. It is noted that these results were achieved with high paving production rates.

Phillip S. Dunston, Bonnie M. Savage, and Fred L. Mannering, Department of Civil and Evironmental Engineering, University of Washington, Box 352700, Seattle, WA 98195-2700, Tel: 206-685-1795, Fax: 206-543-1543, Email: pdunston@u.washington.edu, bonmae@u.washington.edu, flm@u.washington.edu.

991160 "Development of A Method For Early Prediction Of The Asphalt Content Of Hot Mix Asphalt (HMA) By Ignition Test"

Abstract: The ignition test, developed by the National Center for Asphalt Technology (NCAT), has proved to be a fast, pollution free, automated and inexpensive method of determining the asphalt content of a hot mix asphalt (HMA) sample. The time required to perform this test is about 30 to 40 minutes, which is significantly less than the time required to perform a solvent extraction test procedure. However, having the ability to determine asphalt content in 10-15 minutes would allow the technician to identify any problem in mix production much earlier, and thus save a significant amount of time and money. This paper presents the results of a study carried out to develop a method for estimating the asphalt content of hot mix asphalt (HMA) sample within 10to 15 minutes after testing begins. The method consists of determining the prediction factor on the basis of test results from two samples and then predicting the asphalt content of additional samples on the basis of the prediction factor and the asphalt content loss at 10-15 minutes of test. Use of this method is expected to provide a good estimate of the measured asphalt content in less than half the test time. This short cut method should be used for quality control only and should not be used for acceptance or rejection of the mixtures. Conclusions: A simple practical method has been developed to predict the asphalt content of a HMA sample after 10-15 minutes. The method consists of determining the prediction factor on the basis of test results from two samples and predicting the asphalt content of additional samples on the basis of the prediction factor and the asphalt loss after 10 to 15 minutes of test. Use of this method is expected to cut down the testing time by 15 to 30 minutes for quality control testing. This means that with the use of proper prediction factors, the user will be able to determine any change in asphalt content within 10 to 15 minutes of starting the ignition test. The substantial savings in time will translate to early detection of any change in asphalt content and hence significant monetary savings. It should be understood that this procedure is meant for quality control (QC) only, and is not recommended as a tool for quality assurance (QA).Rajib Mallick, CEE Department, Worcester Polytechnic Institute, 100 Institute Road, Worcester, MA 01609, Tel: (508) 831 5289, Fax: (508) 831 5808, Email: rajib@wpi.edu; Elton Ray Brown, National Center for Asphalt Technology, 211 Ramsay Hall, Auburn University, AL 36849, Tel: (334) 844 6244, Fax: (334) 844 6248, Email: rbrown@eng.auburn.edu.

991222 "Rehabilitation Of Ellaville Weigh Station With Ultra-Thin Whitetopping"

Abstract: The Florida DOT constructed the first Ultra-Thin Whitetopping (UTW) to rehabilitate the Ellaville Truck Weigh Station on I-10 in Northwest Florida. This rehabilitation project included the placement of UTW on the existing asphalt pavement which had severe rutting and cracking problems. Nominal layer thicknesses for the UTW were 80 mm and 100 mm. The joint spacings for the UTW panels were 1.2 m and 1.6 m. High early strength concrete was used in this project. Polypropylene fibers were included in the concrete for the sections on the west side of the weighing platform and plain concrete was used on the east sections. Panel joints on the east sections were sealed with silicone sealant while the joints in the west sections were left unsealed. This paper discusses the implementation of the UTW in Florida which includes design, specification and construction. Also addressed is the performance the Ellaville Weigh Station after one year of truck loading, and the predicted life of the UTW. Conclusions: Primary emphasis should be placed on ensuring maximum bond between the UTW and asphalt. Specifying compressive strength, shearing strength at UTW/asphalt interface and rideability as acceptance criteria can produce better performance and ensure smoother ride. UTW panels with 1.2 m and 1.6 m joint spacing seem to provide equal performance. Placing UTW on a 32 mm thick asphalt layer did not show any premature cracking. A preconstruction conference with the contractor is essential to discuss the specific details of UTW. The effect of fibers on performance of the UTW could not be determined. Sealing the joints did not make any difference in the performance of the UTW sections. A one year service life of the UTW at the weigh station is equivalent to 4.8 years of service life on an intersection with medium traffic.

Jamshid Armaghani, and Diep Tu, Florida Department of Transportation, 2006 Northeast Waldo Road, Gainesville, Florida 32609, Tel: (352) 337-3200, Fax: (352) 334-1648, jamshid.armaghani@dot.state.fl.us.

991357 "A Contractor's Experience with Polymer Modified Asphalt in Alabama"

Abstract: The use of polymer modified asphalt binder has increased in the state of Alabama with the requirement for higher Performance Graded (PG) asphalt on high-volume roadways. In 1997, four types of polymer modified asphalt binders (PMAB) were available from suppliers in Alabama: one modified with plastomer wax (EE2), one modified with a reactive elastic plastomer (GEA), and two modified with an elastomer polymer (SBS). A laboratory investigation was undertaken to compare three of the polymer modified asphalts (only one elastomer modified asphalt binder was tested) in terms of: force ductility at 4*C, separation of polymer and asphalt, and laboratory rutting performance of hot mix asphalt (HMA) prepared with each asphalt. Performance testing was also performed on the elastomer polymer (SBS) and the GEA during asphalt production for two roadways in Alabama. Conclusions: Laboratory testing indicates that the use of PMAB in hot mix asphalt can greatly enhance performance of the HMA in comparison to the use of PG 64-22. However, proper production and storage procedures must be followed when using PMAB to prevent separation. Daily separation testing by the PMAB suppliers should be required by the DOT due to the fact that when separation of the PMAB occurs it is a problem for everyone involved. Unforeseen expenses, equipment damage, and possible asphalt pavement failure can occur. The testing results have shown that some PMAB's are more prone to separation than others but that the final product "Hot Mix Asphalt" should benefit from the use of PMAB if the PMAB is handled and produced properly.

Paul Messersmith, Chris Jones and Chris Wells, Superfos Construction (U.S.), Inc. 715 Twitchell Road, Dothan, AL 36303, Tel: (334) 794-2631 Fax: (334) 794-2631 Ext. 310 Email: paulm@Superfos-usa.com.

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IV. CONSTRUCTION: STRUCTURES

991422 "Epoxy Jointing of Precast Prestressed Concrete Segments"

Abstract: Epoxy is normally used between precast segments to fill voids, to keep water from seeping in the joint, to prevent grout from bleeding into the joint from the post tensioning ducts, and to act as a lubricant between the segments. Better and more efficient means of ensuring a good seal between ducts are needed for enhanced protection against rain water, de-icing salts and cross grouting, which may lead to corrosion of prestressing steel. Two new experimental epoxy applications were tested in this study: a top strip recess at the joint that was formed into the concrete during the precast process, and a recessed annulur groove around the duct which provides a distinct guide for the proper amount of epoxy application. The joints were tested with water tanks placed above the joints to measure the seepage of water. Pressurized water was subsequently applied through the ducts, and the amount of pressure loss was measured. The joints were inspected for water that may have escaped from the ducts. Conclusions: Results showed that the current practice of one face epoxy application performed well when properly applied. The epoxy filled annuli provided good protection against grout penetration, coupling between segments, and automatic epoxy clearance around ducts. The epoxy filled top strip was very effective in resisting water penetration, and provided a convenient way to correct alignment and handling damage at the edges. It is recommended that the use of the one face epoxy application should be continued, with the annulus feature added. The top strip feature may not be practical because of maintenance and grinding problems.

Nur Yazdani, Professor of Civil Engineering, Florida A&M University – Florida State University, 2525 Pottsdamer Road, Room 129, Tallahassee, Florida 32310, Phone: (850) 410-6125, Fax: (850) 410-6142, Email: yazdani@eng.fsu.edu.

V. BITUMINOUS MATERIALS

990080 "An Evaluation Of Stripping In Virginia’s Pavements"

Abstract: Virginia has struggled with stripping of asphalt mixes since the 1970’s. Initially, chemical antistripping additives were used; eventually, hydrated lime was required, under certain conditions, when it proved to be effective in a limited set of field tests. The specifications were then changed to require hydrated lime or a chemical additive that could produce a tensile strength ratio (TSR) equivalent to that obtained by using hydrated lime. Because of this change, it was believed that chemical additive manufacturers made improvements to produce a new generation of additives that were superior to those previously available. In 1991, a small field study was initiated in Virginia to determine the performance of the new-generation additives and hydrated lime. The pavements showed significant stripping; therefore, a follow-up survey including 74 sites scattered throughout the state was conducted to verify these findings. Conclusions: The follow-up survey indicated that stripping of asphalt mixes continues to be a problem in Virginia. A high degree of stripping was observed in 30 to 50 percent of the pavements surveyed. Although the initial small field study indicated that hydrated lime was more beneficial than chemical additives the follow-up survey that included a large number of sites did not verify this finding. Also, there was no significant difference in stripping between different types of mixes. The air voids level of the pavements was higher than desirable which might have contributed to some of the excessive stripping.

George W. Maupin, maupingw@vdot.state.va.us.

990110 "Use of RAP in Superpave HMA Applications"

Abstract: This research program evaluated the possibility of splitting RAP stockpiles then using the coarser RAP fraction in a typical 12.5 mm below the restricted zone Superpave gradation. The finer RAP fraction was used in an above the restricted zone 12.5 mm Superpave gradation. Two sources of RAP (Georgia and Minnesota) were used so that a wide range of asphalt and aggregate properties would be represented. Screening the RAP allowed up to 40 percent of the coarse RAP fraction to be used and still meet below-the-restricted zone Superpave gradation and volumetric requirements. This was mainly due to the significant reduction in the finer aggregate fractions, especially the minus 0.075 mm material. The use of RAP in these mixtures resulted a savings in the required neat asphalt of between 18 to 25 percent. A noticeable increase in mixture tensile strength with as little as 15 percent RAP was seen. This change in mixture properties suggested that a softer grade of neat binder might be needed. A maximum of 15 percent of the fine RAP fraction was used to produce an acceptable above-the-restricted zone Superpave gradation. The net savings in neat asphalt content was 25 percent. Little change was seen in tensile strengths due to the addition of this RAP fraction. However, there was a substantial increase in mixture stiffness at intermediate to warm temperatures. This increase was also seen as a 20 percent reduction in the APA rut depth when RAP was used. The indirect tensile creep compliance decreased when RAP was added. While there was little difference in compliance at -20oC, there was a decrease of about 30 and 50 percent at -10 and 0oC test temperatures, respectively. Conclusions: Using RAP in mixtures, even at low percentages, require an evaluation of the composite mixture properties in order to accurately assess the need for a change in neat asphalt grade.

Mary Stroup-Gardiner, and Chris Wagner, National Center for Asphalt Technology, 211 Ramsay, Auburn University, Alabama 36849; Phone (344) 844-6280, Email: marysg@eng.auburn.edu.

990163 "Blending Charts Based on the Performance-Graded (PG) Asphalt Binder Specification"

Abstract: In this study, one binder was laboratory aged with the RTFO and PAV to simulate the aged binder in the RAP. The aged binder was blended with two soft binders and two rejuvenated materials. Ten blended and rejuvenated binders were characterized with the PG binder parameters such as G* (complex shear modulus), d (phase angle), S (stiffness), and m-value (creep rate). The relationship of the PG binder criteria (G*/sin d, G*.sin d, S, and m-value) versus amount of soft binders and rejuvenators in the blends was studied. Conclusions: A linear relationship was found sufficient accurate for prediction of the PG parameters and criteria of blended and rejuvenated binders versus proportion of new binder/recycling agents in blends. Two type of blending charts can be used for selection of proper type or amount of soft binder/recycling agents in the design of mixtures containing RAP. The first method is based on a linear relationship for PG performance criteria (G*/sin d, G*.sin d, S and m-value) versus proportion of soft binder/recycling agents. The second method is based on linear relationship for change in temperatures that PG criteria were satisfied versus proportion of soft binder/recycling agents in blends. In prediction of the PG testing parameters for blended binders, the interaction criteria a lower coefficient of correlation (R2) and higher standard error of mean were found for binders blended with recycling agents than binders blended with soft binders. This can be attribute to blending two materials with high viscosity differences.

Hamid R. Soleymani, North Central Superpave Center, Purdue University West Lafayette, IN. 47906 Tel # 765 463-2317 Email: soleyman@ecn.purdue.edu; Hussain U. Bahia, University of Wisconsin-Madison, Email: bahia@engr.wisc.edu Arthur T. Bergan, University of Saskatchewan, Saskatoon, Canada.

990498 "Collaborative Evaluations of Low Temperature Superpave PG Asphalt Binders"

Abstract: Superpave developed the specifications and selection of Performance Graded Asphalt Binders to address performance in the field. To facilitate the implementation of Superpave, highway agencies are sharing information and working with industry. Wisconsin, Iowa, and Minnesota have collaborated to develop a joint certification program to streamline the process and promote partnering with suppliers. The low temperature grading of the Superpave asphalt binders is of special interest in very severe climates. This paper looks at several projects which have incorporated Superpave asphalt binders, including new construction, reconstruction, overlays on rehabilitated highways and overlays on existing highways. The projects vary from low volume highways to high volume interstates to an airport in an extremely severe climate. The projects, which have been in place several years, have been evaluated for their field performance, especially for behavior at low temperature. The new asphalt binders have been found to increase the resistance to thermal cracking on newly constructed roads and to inhibit reflective cracking on overlays. Conclusions: Of specific interest in the severe climates, the low temperature performance of the Superpave Performance Graded Asphalt Binders has shown significant reduction in thermal cracking on both new construction and reconstruction. 1) On overlays over rehabilitated pavement applications such as pulverized base, the PG asphalt binders have shown value by reduction in thermal cracking. 2) Similarly, PG asphalt binders have shown value by retarding reflective cracking for up to three years on overlays such as the International Falls Airport, CSAH 30 in Blue Earth County, Minnesota, and TH 63 in Lake County, Wisconsin. It is important to use this information in comparison with newer asphalt binder selection guidelines adopted with the new low temperature algorithm.

Dan Wegman, Koch Materials Company, P.O. Box 64596 St. Paul, MN 55164-0596; Jack Weigel, Payne and Dolan, P.O. Box 781, Waukesha, WI 53187; and Alan Forsberg, Blue Earth County Engineer, 35 Map Drive, Mankato MN 56001.

990512 "The Difficult Nature of Minimum VMA: A Historical Perspective"

Abstract: Several researchers have recently discussed problems achieving the minimum voids in the mineral aggregate (VMA) requirements specified in Superpave volumetric mix design. The minimum VMA requirements are often difficult to achieve; they can "fail" mixes that have acceptable performance records, and they may require a higher asphalt content leading to higher project costs. To address these issues the background and logic behind the minimum VMA requirement are re-examined. A review of asphalt mix design methods shows that a minimum VMA requirement was not used until the 1950s, when Dr. Norman W. McLeod almost single-handedly advanced VMA to a critical design parameter. In 1962, The Asphalt Institute specified VMA as a Marshall mix design requirement, but as late as 1985 it was still misused by many highway agencies. Only through the Strategic Highway Research Program (SHRP) and the implementation of Superpave has the minimum VMA requirement become a design standard. The literature review uncovered several problems with specifying minimum VMA: (1) The field data from which the minimum VMA requirements were established could not be found in the literature, (2) The original VMA requirements were based on Marshall compaction, and (3) The precision of the testing necessary for measuring VMA is not good enough for rigid enforcement of VMA specifications. In light of the information presented, it seems clear that the minimum VMA requirements need to be re-examined in light of Superpave and validated with field data.

Brian J. Coree, Ph.D., P.E., Assistant Professor, Iowa State University, 484 Town Engineering Building, Ames, IA 50011, Tel: 515-294-3973, Fax: 515-294-8216, Email: bcoree@iastate.edu; and Walter P. Hislop, Graduate Assistant, Iowa State University, 484 Town Engineering Building, Ames, IA 50011.

990513 "HMA Volumetrics Revisited - A New Paradigm"

Abstract: As early as 1905, Richardson recognized the importance to performance of the relative proportions, by volume, of the material components of bituminous mixtures. In the 1940's Marshall explicitly addressed the volumetric percentages of air voids, Va, and of the degree of void saturation by asphalt, (VFA). In the late 1950's McLeod clearly demonstrated and justified the appropriate aggregate specific gravities to be used in volumetric computations, and emphasized the importance of the combined volumes of the air voids and effective asphalt binder (VMA). These various volumetric parameters have since formed a principal part of the Marshall design method and have, more recently been enshrined into the Superpave system. This paper seeks to revisit the definitions of the various volumetric parameters and their inter-relationships. It develops an instructive and useful chart with which mixtures of different volumetric characteristics may be compared, and through trajectory analysis, reduced to a common basis. A further simple graphical method is developed that may be used to analyze, volumetrically, mix designs both Marshall and Superpave. This latter method can be used as a point-estimate method to identify the binder content which will yield any given air void content. While the paper offers no new technology, it presents old information in a new way - a new paradigm.Brian J. Coree, Ph.D., P.E., Assistant Professor, Iowa State University, 484 Town Engineering Building, Ames, IA 50011, Tel: 515-294-3973, Fax: 515-294-8216, Email: bcoree@iastate.edu.

990842 "Evaluating Asphalt Mixtures Using Superpave Performance Tests"

Abstract: Recent research has indicated that the Superpave performance models, and some of the tests, have critical errors that make performance prediction impossible. Still, a substantial amount of testing has been conducted since 1994 to analyze the performance properties of asphalt mixtures. This data can be used to calculate mechanical properties that permit relative determinations of asphalt mixture stiffness and rutting susceptibility. The objective of this paper is to provide documentation of performance test results of various asphalt mixtures tested since 1994. It is intended that these values can provide guidance to the user indicating how an asphalt mixture compares to other mixtures with performance history. The paper also considers the effect of changes in mixture components, sample reheating, and type of Superpave gyratory compactor on the mechanical properties. Conclusions: The complex shear modulus (G*) and maximum shear strain (gmax) of an asphalt mixture, determined from the FSCH and SSCH tests respectively, appear to react as expected with changes in asphalt content. Values from testing of laboratory-produced mixtures generally indicate that G* decreases and gmax increases as asphalt content increases. The type of SGC and sample type (original or reheated) did not appear to have a consistently significant effect on the G* and gmax of the field-produced asphalt mixture samples. Data collected from one project indicates that the performance test results can be used to indicate changes in material properties. Analysis performed to date generally indicates that specimens prepared from field-produced asphalt mixture, using the SGC, have lower G* and higher gmax values (measured at 40(C) than specimens produced from laboratory prepared mixture.

R. Michael Anderson, Asphalt Institute; John R. Bukowski, FHWA; and Pamela A. Turner, Asphalt Institute, P.O. Box 14052, Lexington, KY, 40512, Tel: (606) 288-4984 FAX: (606) 288-4999 Email: manderson@asphaltinstitute.org.

990955 "Evaluation of the Use of the Hamburg Wheel-Tracking Device for Moisture Susceptibility of Hot Mix Asphalt"

Abstract: Laboratory testing of hot mix asphalt (HMA) evaluating moisture susceptibility has improved over the past several decades. Within the past 8 years, the Hamburg Wheel-Tracking Device (HWTD) has gained notoriety in evaluating HMA for moisture susceptibility. There are no standard test methods or specifications established for this testing device. This study evaluated laboratory repeatability of the test, testing configuration, test temperature, and capability to evaluate effects of anti-stripping additives in HMA. The HWTD has shown to be very repeatable where six replicate tests provided consistent test results. The device yielded repeatable results for mixtures produced with different aggregates and with test specimens fabricated by different compacting devices. The conventional testing configuration was altered such that cylindrical test specimens fabricated with a Superpave Gyratory Compactor (SGC) could be used in lieu of rectangular slabs. Results indicate that cylindrical specimens compacted with the SGC could be used for moisture evaluation in the HWTD for comparative evaluation of one material to another. Typically, testing with the HWTD is performed at 50oC. Six mixtures were fabricated with and without anti-stripping additives and tested at 40oC and 50oC. Mixtures were modified with hydrated lime and a liquid anti-stripping additive and all mixed with AC-20. Test results have shown mixtures with hydrated lime to perform the best followed by those modified with liquid anti-stripping additive and worst were those without any additive at 40oC. Inconsistent trends were seen at 50oC. The HWTD properly predicted performance of the mixtures modified with anti-stripping additives at 40oC.

Richard Izzo, Texas Department of Transportation, 2311 W. Rundberg Lane, Suite 100, Austin, TX 78758, Tel: (512) 232-1904, Fax: (512) 232-1939, Email: rizzo@mailgw.dot.state.tx.us; and Maghsoud Tahmoressi, Texas Department of Transportation, 2311 W. Rundberg Lane, Suite 100, Austin, TX 78758, Tel: 512-232-1903, Fax: 512-232-1939, Email: mtahmor@mailgw.dot.state.tx.us.

991321 "Recovery and Testing of RAP Binders from Recycled Asphalt Pavements"

Abstract: Extraction and recovery of asphalt cement from mixtures is a routine task in most asphalt laboratories. Characterization of extracted asphalt binder and aggregate is important for design, quality control, performance prediction and research purposes. Different methods, equipment and solvents for extraction of asphalt binders have significant effects on the properties of the extracted asphalt binder and aggregate. Under NCHRP 9-12, Incorporation of Reclaimed Asphalt Pavement in the Superpave System, a study was conducted to review the variables in extraction and recovery methods. One objective of this study was to evaluate different extraction and recovery methods and determine the best to use for the NCHRP 9-12 study. The second objective was to determine if additional aging of recovered binders is necessary when conducting mix designs in the laboratory. The experimental matrix developed included two different extraction procedures, two recovery methods and three different solvents. Properties of extracted aggregates and asphalt binders from two different Reclaimed Asphalt Pavements (RAP) were studied. The results demonstrate significant variability on properties of extracted asphalt binder with different solvents, extraction and recovery methods. However, the extracted RAP aggregate gradation was not significantly different with different methods and solvents. The aging of the recovered binders demonstrated insignificant changes for the blending of RAP binders. Conclusions: There was no significant difference in the gradation of the extracted aggregates. The asphalt content varies with different methods, probably due to residual solvent or fines in the asphalt binder. The DSR showed the Centrifuge-Abson-TCE method had the highest coefficient of variance, however, all methods exhibited linear behavior. The Asphalt Institute modification of AASHTO TP-2 was selected for use in the 9-12 project because of repeatability and health and safety issues. Testing showed that no additional aging of RAP binders is necessary for use in laboratory blending charts.

Robert L. Peterson, R. Michael Anderson, Hamid R. Soleymani, Rebecca S. McDaniel Asphalt Institute 2696 Research Park Dr. Lexington, KY 40511, Tel: 606-288-4977 Fax: 606-288-4999 Email: bpeterson@asphaltinstitute.org.

991336 "Effect of Gradation on Asphalt Mixture Performance"

Abstract: Phase I of the National Pooled Fund Study No. 176, "Validation of SHRP Asphalt Mixture Specifications Using Accelerated Testing," has been completed. One topic addressed in this project was the effect of gradation on asphalt mixture performance. The purpose of Phase I was to evaluate sensitivity of tests to changes of gradations within the framework of Superpave aggregate specifications. Tests reported in this paper are prototype scale accelerated pavement tests, laboratory scale wheel tracking tests and triaxial tests. Test results are reported for mixtures prepared with one common asphalt (PG 64-22), two coarse aggregates (limestone) and one limestone. These materials were combined to produce mixtures with gradations above, through and below the restricted zone. Analysis indicates that the tests are sensitive to changes in gradations and aggregate types. Conclusions: Test results show both compaction level and asphalt content influence mixture strength. In general, higher compaction results in higher strength. This statement is only valid when the asphalt content is equal to or lower than the design asphalt content selected through Superpave mixture design criteria. As a result, the triaxial compression test can be used to evaluate the stability (rutting potential) of asphalt mixtures with different gradations, bulk densities, and asphalt contents. Test results from APT, PURWheel and triaxial tests indicate that the accelerated tests being used are in fact sensitive to changes in the volumetric properties of asphalt mixture. However, the effect of mixture gradation is compounded with the interrelationships between aggregate properties and mixture volumetric properties as well as the selection of design asphalt content.

John Haddock, Changlin Pan, Aiwen Feng, and Thomas D. White, School of Civil Engineering, Purdue University, West Lafayette, IN 47907, Tel: (765) 494-2215, Fax: (765) 496-1364, Email: tdwhite@ecn.purdue.edu.

991338 "Effect of Flat and Elongated Coarse Aggregate on Characteristics of Gyratory Compacted Samples"

Abstract: This investigation examined the impact of varying levels of Flat and Elongated (F&E) particles on the gyratory compaction characteristics in a standard bituminous mixture. Compaction characteristics involve the effect of F&E particles on the void development in the gyratory compactor as well as the breakdown characteristics. F&E particles could also impact the performance characteristics of the compacted mixtures. This investigation examined F&E particles in typical Illinois surface mixtures. Two coarse aggregate sources, a dolomite and a crushed gravel were used in this study. A cubical mixture was prepared using all particles having a F&E ratio less than 3:1 and baseline compaction characteristics were established. Coarse aggregates were individually measured to produce aggregate particles with measured F&E ratios less than 3:1, between 3:1 and 5:1, and greater than 5:1. The coarse aggregates in the cubical gradation were replaced with varying percentages of the same size aggregate with F&E ratios in the 3:1 and 5:1 range. These mixtures were compacted and the volumetric and gyratory characteristics were compared. Solvent extractions and binder ignition samples were obtained to indicate the relative breakdown in aggregates achieved with the varying percentages of the F&E particles. The testing indicates the changes produced when differing percentages of F&E particles are introduced into a mixture. When combined with performance testing, these data will provide a valid base upon which to base recommended levels of allowable F&E particles in an asphalt mixture. Conclusions: increased levels of F&E particles give increased air voids in gyratory compacted HMA samples; increased levels of F&E particles give increased VMA and VFA in gyratory compacted HMA samples; the gyratory compaction slope is increased with increased levels of F&E particles; the locking point of the compacted mixture is not effected by the amount of F&E particles with the use of dolomite aggregates; the locking point of the compacted mixture is changed when gravel aggregates are used because of the change to the coarse aggregate structure; increased amounts of F&E give more breakdown and fracture of aggregate particles during gyratory compaction; using soft F&E aggregates caused breakdown of the coarse aggregate to produce a coarse fine aggregate which increased the void structure of the mixture; using hard F&E aggregates caused breakdown of the coarse aggregate to produce a void in the coarse aggregate structure.

S. H. Carpenter, 205 N Mathews, Urbana, IL 61801, Phone 217-333-4188, Fax: 217-333-1924, email: scarpent@uiuc.edu.

991390 "Low Temperature Evaluation of Kentucky PG 70-22 Asphalt Binders"

Abstract: A research study was initiated to ascertain if all PG 70-22 binders would perform the same in an asphalt mixture in Kentucky, regardless of method of manufacture of the binder. Five PG 70-22 binders and one PG 64-22 binder (control) were incorporated into an asphalt mixture through a hot-mix asphalt plant. Test sections were placed for each binder. Mixture mechanical property tests included repeated shear test at constant height (RSCH), frequency sweep test at constant height (FSCH), and indirect tensile creep test (ITC). These tests were chosen to evaluate the high, intermediate, and low temperature properties of the asphalt mixtures. Only low temperature properties are discussed in this paper. Thermal stress analysis techniques permitted the critical mixture temperature for thermal cracking to be compared to critical binder temperatures. Conclusions: While the critical binder temperature (calculated from BBR stiffness) matched reasonably well with the critical mixture temperature, the critical binder temperature calculated from BBR m-value did not match as well. The m-value critical temperature underestimates the mixture critical temperature. Since m-value normally controls the low temperature grade of the asphalt binder, it appears that the binder specification is conservative with respect to single-event thermal cracking compared to mixture results. The broad range in mixture critical temperatures indicates that not all of the asphalt binders in this research study may perform the same. Although testing indicated that these asphalt binders were nominally PG xx-22 binders, the actual low temperature grade of the asphalt binders in this study varied from -15(C to -28(C. The apparent relationship between critical binder temperature (calculated by BBR stiffness) and critical mixture temperature, indicates that differences in estimated performance for the asphalt binders in this study may be more related to actual binder stiffness than method of manufacture.

R. Michael Anderson, Pamela A. Turner, and Dwight E. Walker, Asphalt Institute, P.O. Box 14052, Lexington, KY, 40512, Tel: (606) 288-4984 FAX: (606) 288-4999 Email: manderson@asphaltinstitute.org.

991419 "Municipal Implementation of Superpave Technology"

Abstract: The reconstruction of 30 kilometres of County Road 2 by the County of Frontenac in 1996, provided the opportunity for municipal implementation of Superpave performance graded asphalt cement and volumetric mix design technology. The Superpave surface course mix was placed over the cold in-place recycled asphalt pavement and compacted in a manner similar to conventional asphalt mixes, with the application of light soap solution on the compaction equipment to avoid pick-up associated with the polymer modified performance graded asphalt cement. The Superpave mix properties for trial batches, prior to paving, were verified using a Superpave gyratory compactor. Basic mechanistic properties (resilient modulus, permanent deformation and resistance to fatigue) of the Superpave surface course mix were measured using the Nottingham Asphalt Tester (NAT). Three long-term performance monitoring test sections were established at representative locations on County Road 2. The test sections performance monitoring includes: visual distress surveys; structural capacity testing using the Falling Weight Deflectometer; and transverse profiles using the digital incremental profilometer (DipstickR).

Conclusions: The reconstruction of 30 kilometres of deteriorated asphalt pavement by the County of Frontenac in 1996 using a Superpave 12.5 mm nominal size asphalt mix over the cold in-place recycled asphalt pavement is considered to be very successful. Three years after reconstruction, the pavement is in very good condition, exhibiting no significant surface distresses or rutting. There are no reflective or low temperature cracks visible. The pavement’s structural condition is also good to very good. Further monitoring of pavement condition for the test sections has been recommended to the County.

Don Brooks, County of Frontenac, Ontario, Canada; John Emery, David Hein, and Ludomir Uzarowski, John Emery Geotechnical Engineering Limited, Consulting Engineers #1, Woodbine Downs Boulevard, Toronto, Ontario M9W 6Y1, Canada, Tel: (416) 213-1060 Fax: (416) 213-1070 Email: jegel@comnet.ca.

991429 "Evaluation of Aggregate Size Characteristics in Stone Matrix Asphalt (SMA) and Superpave Mixtures"

Abstract: With any hot-mix asphalt (HMA) pavement, the applied loads must ultimately be carried by the aggregate. In addition to meeting minimum aggregate quality requirements, the proper aggregate grading must be used if the HMA is to perform satisfactorily in service. The aggregate gradation is important to ensure that the proper aggregate structure and mixture volumetric properties are achieved. This paper presents the findings of an evaluation of aggregate size characteristics, namely nominal maximum aggregate size (NMAS) and gradation, in Stone Matrix Asphalt (SMA) and Superpave mixtures. The study objectives were: 1) Verify that the SMA mix design procedure developed for the NCHRP 9-8 (1) project was applicable to nominal maximum aggregate sizes other than 19 mm, and 2) Compare mixture properties of SMA and Superpave mixes having the same NMAS. Mixture volumetric properties, wheel tracking and permeability tests were used to make comparisons. The test data indicated that the NCHRP 9-8 mix design approach for SMA mixes was indeed appropriate for various nominal maximum aggregate sizes. Differences in the wheel tracking and permeability results of the SMA and Superpave mixes were observed. Permeability results for the SMA mixes showed that for a given NMAS, mixes with smaller break point sieves were less permeable. The Superpave mixes having gradations above the restricted zone exhibited the least amount of rutting and were the most impermeable. Conclusions: The data generated by this study support the following conclusions and recommendations: The SMA mix design procedure developed for NCHRP Project 9-8 is applicable for various nominal maximum aggregate size (NMAS) mixtures including 19 mm. Based on this work, SMA gradation bands were developed for the following NMAS: 25 mm, 19 mm, 12.5 mm, 9.5 mm and 4.75 mm. These gradation bands have been submitted to AASHTO for acceptance. APA wheel tracking results indicated that all mixtures rutted less than 5 mm when tested at 55oC. This is significant since this is the APA criterion used by the Georgia Department of Transportation as one of the design acceptance requirements for high performance mixes. While all the mixtures exhibited good resistance to rutting, it was observed that Superpave mixes having gradations above the restricted zone (ARZ) generally performed better than the others tested. An exception to this was the 25 mm gradation below the restricted zone (BRZ) which performed as well as the ARZ mixture. These data suggest that gradations above the restricted zone should not be ignored when designing Superpave mixes. The Superpave mixes were determined to be less permeable than the SMA mixes. Of the two Superpave mix types, the ARZ gradations were less permeable than the BRZ gradations. Also, the 9.5 mm NMAS mixtures were determined to be less permeable than the 25 mm NMAS mixes. This is important since excessive permeability of HMA pavements can result in serious moisture damage problems. It was noted that the permeability test used in the study is still currently being developed. However, the data generated indicated that SMA and coarse graded Superpave mixes (i.e. those having gradations below the restricted zone) may require more compaction in the field to achieve lower in-place voids. Specifying lower in-place voids should minimize permeability and the susceptibility for water damage.

Todd A. Lynn, APAC Materials Services, 3005 Port Cobb Drive, Smyrna, Georgia, 30080, Tel: (404) 603-2777, Fax: (404) 603-2770, Email: talynn@ashland.com; E. Ray Brown, and L Allen Cooley, Jr., National Center for Asphalt Technology, 211 Ramsay Hall, Auburn University, Alabama, 36849, Tel: (334) 844-6228, Fax: (334) 844-6240, Email: coolela@eng.auburn.edu.

991456 "Comparison of Laboratory Wheel Tracking Test Results to WesTrack Performance"

Abstract: In 1990, members of the Federal Highway Administration (FHWA) participated with other industry and highway agencies in a European Asphalt Study Tour to examine pavement technology. One of the technologies brought back from this tour was laboratory wheel tracking devices. However, the ability of these devices to predict or rank field performance has been questioned. WesTrack provides a unique opportunity for comparing accelerated laboratory wheel tracking devices to full scale pavement performance under controlled conditions. The three devices examined in this paper are the Asphalt Pavement Analyzer (APA), the French Pavement Rutting Tester (FPRT), and the Hamburg Wheel-Tracking Device (HWTD). WesTrack is a 2.9-km oval test track with each tangent consisting of 13-70m sections. Samples for laboratory evaluation using three wheel-tracking devices were taken from the 5-m sampling segments of the rehabilitated sections; ten sections placed in the summer of 1997. Based on the data and analyses in this study, the three laboratory devices studied examined satisfactorily correlate with the permanent deformation of the WesTrack sections studied. The correlations are 89.9%, 83.4%, and 90.4% for the APA, FPRT, and HWTD, respectively. The devices, although not perfect in predicting and/or ranking section performance, did exhibit increased variability with poorer performance. This increased variability with mean permanent deformation or creep rate, allows for a rational method to establish mixture design specifications for all three devices. The procedure exhibited in this paper is flexible, allowing for an agency to select the level of performance desired. It should be stressed that the examples for the three devices used an arbitrary level of performance. There are two very important criteria that need to be emphasized. The first criteria is the selection of an appropriate test temperature that reflects the in-service temperature which the pavement will be expected to perform. The second issue not discussed is the assumption of laboratory compaction simulating field compaction. Studies are currently being conducted at the FHWA have shown significant discrepancies between field compaction and several laboratory compaction devices. This compaction issue should be resolved before implementing a performance test in a mixture design process.

R. Christopher Williams, Federal Highway Administration, Turner-Fairbank Highway Research Center, 6300 Georgetown Pike, McLean, VA 22101, 703-285-1018 (voice), 703-285-2767 (fax), Ronald.C.Williams@fhwa.dot.gov; and Brian D. Prowell, P. E., Virginia Transportation Research Council, 530 Edgemont Road, Charlottesville, VA 22903, 804-293-1919 (voice), 804-293-1990 (fax), ProwellBD@vdot.state.va.us.

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VI. CEMENT AND CONCRETE

990400 "The Virginia Approach to Evaluation ASR-Resistant Concrete"

Abstract: Difficulties have been encountered in accurately classifying Virginia aggregates with regard to their potential reactivity. Consequently, VDOT instead is attempting to identify and use cementitious materials that prevent or hinder ASR. These materials, pozzolans and slag, have been shown to reduce both ASR and permeability, resulting in more durable concrete. Two newly developed tests were used to evaluate the effects of cementitious materials (ASTM C 1260 and C 1293) on the ASR potential of construction aggregates. The results of these tests were compared with the results of a more accelerated test (ASTM C 441) that uses an extremely reactive synthetic aggregate. Differences in test results were noted: the C 441 test, using more stringent criteria, predicted higher replacement levels for a given pozzolan or slag with a portland cement of a given alkali content than are interpreted from the C 1260 or the C 1293 tests. However, although a greater degree of confidence in long-term performance can be placed in material levels that "pass" the C 441 test, the material replacement levels that meet the criteria specified in the C 1260 and C 1293 tests have been generally observed to provide acceptable performance in the field. Conclusions: In addition to using ASTM C 441 to evaluate cementitious materials; they can also be tested with the proposed construction aggregates using C 1260 and C 1293. The replacement levels predicted by C1260 and C1293 for Virginia aggregates are in order with levels generally observed to provide good field performance. These levels are lower than those predicted by C 441 results using the VDOT limit of 0.10% at 56 days.

D. Stephen Lane, Sr. Research Scientist, Virginia Transportation Research Council, 530 Edgemont Rd., Charlottesville, VA Tel: 804-293-1953; Fax: 804-293-1990; Email: dsl5e@virginia.edu or dslane@vdot.state.va.us.

990544 "Cracking Damage/ Deterioration and Rehabilitation Considerations of Some Birmingham, AL Interstate Bridge Decks"

Abstract: The Alabama Department of Transportation (ALDOT) has over 4,830 m (3 miles) of major interstate bridges (3 - 5 lanes wide) near downtown Birmingham with significant levels of deck cracking and deterioration. The bridges are part of the I65 and I59 interstate highway system through the city, and are approximately 27 years old. It appears that the deck cracking is primarily the result of (1) early drying and thermal shrinkage, (2) early concrete obstructed settlement, (3) thin and flexible decks, (4) light and flexible superstructures, and (5) heavy traffic volume and loadings. Deck condition rating vs. age and crack classification/width vs. age curves are presented for three typical bridge decks, along with a photographic portrayal of the state of deck cracking and deterioration. Comparisons of experimental and theoretical load-deflection behavior of two of the bridges are also presented. The rehabilitation or replacement (R/R) of the bridge decks (approximately 55,740 m2 (600,000 ft2)) is a matter of great concern to the ALDOT. Actions that they are currently taking, and/or plan to take are also presented. Conclusions: The ALDOT must make a decision on rehabilitation actions for the Birmingham decks in the near future. Toward this end, they are looking closely into the following: what other states and highway agencies do in similar cases; traffic demands and planning to identify the need for additional lanes on these bridges in the near future (if additional lanes are justified, they will be added first to ease the traffic congestion during later staged-construction deck R/R); an assessment of remaining fatigue/service life of the steel girder superstructures through field strain gage measurements, and by laboratory fatigue testing of girders extracted from bridges being take out of service; developing the capabilities to perform punching shear load testing within their Bridge Load Testing Section to allow the assessment of punching shear capacity and the imminence of deck structural failure via punching shear; assessing the state of delaminations and deterioration of the existing decks in order to assess the viability of employing deck overlays as a viable and effective rehabilitation strategy; placement of test sections employing different rehabilitation strategies (deck replacements and deck overlays) to evaluate their construction friendliness, requirements for traffic constraints, costs, and performance and estimated longevity when placed in a staged and rapid construction manner.

G. E. Ramey, Feagin Professor of Civil Engineering, Dept. of Civil Engineering, Harbert Engineering Center, Auburn University, AL 36849, Tel: (334) 844-6292, Fax: (334) 844-6290, Email: geramey@eng.auburn.edu.

990770 "Investigation of Design Parameters Affecting Transverse Cracking in Jointed Concrete Pavements (JCP’s): A Field Study"

Abstract: Environmental effects and repetitive traffic applications can lead to the development of transverse cracks in JCP’s. Maintaining adequate aggregate interlock load transfer across these cracks is essential to preserving the functional and structural integrity of these pavements. The objectives of this study were to determine the design parameters that significantly affect transverse cracking and to demonstrate methods available for evaluating cracked pavements. Field data collected from in-service JCP’s located throughout southern Michigan was used to accomplish these objectives. Joint spacing, coarse aggregate type, shoulder type, and pavement temperature were found to have significant effects on transverse crack development and/or performance. The surface texture of crack faces was assessed using a promising new test method called Volumetric Surface Texture (VST) testing. VST results provided an indication of the aggregate interlock potential of pavements containing various aggregate types. Three performance parameters capable of mechanistically characterizing crack performance were discussed. A relatively simple procedure was described for determining these parameters and evaluating crack condition. Field data was also used to demonstrate and validate a voids analysis procedure. This procedure estimates the potential for loss of support near cracks and joints, thus allowing for proper rehabilitation actions to be taken prior to manifestation of additional distresses. Conclusions: Several findings were made regarding the effects of JCP design parameters on traverse cracking: Longer joint spacing leads to a greater number of transverse cracks per slab; pavements containing slag or recycled concrete coarse aggregate appear to have more transverse cracks than those using natural gravel or carbonate aggregates; natural gravel pavements having tied concrete shoulders demonstrated significantly fewer transverse cracks than those having asphalt shoulders; recycled pavements having concrete shoulders with sympathy joints were found to have a significantly greater number of cracks than those having concrete shoulders without such joints; VST testing proved to be a promising means of assessing crack face surface textude and aggregate interlock potential. Results agreed with the intuitively reasonable notion that cracks propagating round aggregates lead to a rougher surface texture than cracks propagating through aggregates. Carbonate and slag specimins were found to have smooth surface texture, wheras natural gravel specimins had rough texture; LTE, AGG and Pt were noted to be three parameter that characterize crack performance. A simple procedure was described for determining parameter values and assessing crack condition. This procedure requires developmnet of LTE-AGG and LTE-Pt plots for selected combinations of k and ? ;a voids analysis procedure, which allows for detection of loss of support near cracks and joints, was described. Data from this study showed that faulted cracks had a significantly higher average x-intercept than cracks without faulting.

Michael A. Frabizzio, Graduate Research Assistant, Department of Civil and Environmental Engineering, Michigan State University, 3546 Engineering Building, East Lansing, MI 48824; Neeraj J. Buch, Assistant Professor, Department of Civil and Environmental Engineering, Michigan State University, 3546 Engineering Building, East Lansing, MI 48824.

990934 "Investigation of Very Early Strength Portland Cement Concrete Suitable for Patching Rigid Pavements"

Abstract: The time required for a concrete mixture to achieve a minimum compressive strength influences the timing of opening a repaired road to service. Drying shrinkage causes stress in the patch that leads to early failure. An investigation was performed to develop concrete mixtures capable of developing high early strength combined with relatively low shrinkage characteristics. These concrete mixtures are intended for patching portland cement concrete, rigid pavement and bridge decks. The investigation involved varying the mixture proportions with different combinations of accelerator and superplasticizer and assessing concrete properties in both the hardened and fresh states. The superplasticizer used is a polycarboxylate comb polymer based admixture. Based on results from the experimental program, mixture designs are recommended for patching concrete pavement where very early strength with minimal shrinkage is required. This paper also highlights prominent differences between the recommended concrete mixture proportions and a concrete material in commercial use. Conclusions: A Very Early Strength concrete was achieved that possesses significantly reduced shrinkage and improved finishing and workability characteristics when compared with a mixture design based on the SHRP-C-363 report. Reducing the cement factor in the mixture can significantly reduce drying shrinkage. At high dosage rates the polycarboxylate comb polymer superplasticizer retarded the mixtures at early age.

Chris Ramseyer, Graduate Research Assistant, The University of Oklahoma, 202 West Boyd, Room 334, Norman, OK 73019, Tel. (405) 843-9843 Fax: (405) 840-1990 Email: ramseyer@ou.edu; Bruce Russell, Ph.D., Assistant Professor, The University of Oklahoma, 202 West Boyd, Room 334, Norman, OK 73019, Tel. (405) 325-1416 Fax: (405) 325-6826, Email: brussell@ou.edu; and Tom Bush, Ph.D., Assistant Professor, The University of Oklahoma, 202 West Boyd, Room 334, Norman, OK 73019, Tel. (405) 325-1415 Fax: (405) 325-5911.

990939 "Influence of Alkaline Earth Silicate Admixture on Durability of Pennsylvania Turnpike Bridges"

Abstract: Chlorides from deicing salts are the primary cause of premature corrosion of reinforcement in concrete bridge decks. An alkaline earth silicate admixture can reduce the permeability of concrete preventing ingress of chlorides, delaying the onset of rebar corrosion, and therefore increasing the design life of bridges. The performance of an alkaline earth silicate admixture in bridge decks in-service for greater than twenty-five years is compared to identical control bridges of comparable age. Visual inspection reveals serious deterioration in the control specimens. Control bridge decks reveals cracks, delaminations and spalling in many of the precast deck panels. In the bridges with the alkaline earth silicate admixture, there is minimal visible deterioration. The goal of this research is to identify and characterize the effect of this alkaline earth silicate admixture in in-service bridge decks. Chemical and microscopic techniques are used to determine the nature of the alkaline earth silicate admixture in hardened concrete. Water and chloride ion permeability tests are performed to quantitatively determine the relative effects between control concrete and concrete containing the alkaline earth silicate admixture. Testing has shown that the alkaline earth silicate admixture has chemical characteristics enabling it to react with portland cement and control the microstructural development in concrete. Quantitative tests for permeability and Environmental Scanning Electron Microscopy (ESEM) reveals a microstructure that is more continuous and interlocked than that of control samples, indicating that the alkaline earth silicate admixture reacts with cement to provide a microstructure that is less permeable. The resulting microstructure has resulted in a nearly pristine bridge deck after twenty five years, wheras the control decks are at the very end of their service life because of severe corrosion and delamination.

Paul J. Tikalsky, Ph.D., P.E., Associate Professor, The Pennsylvania State University, Research Office Building, University Park, PA 16802 (814) 863-5615 Fax: (814) 865 – 3039, Tikalsky@psu.edu; Barry Scheetz, Ph.D., Professor of Materials, Materials Research Lab, The Pennsylvania State University, University Park, PA 16802 (814) 865-3539, bes1@alpha.mrl.psu.edu.

991064 "Influence of Total Aggregate Gradation on Freeze-Thaw Durability and Other Performance Measures of Paving Concrete"

Abstract: Transportation-related agencies are experimenting with increased control of aggregate gradation in their concrete pavement specifications. This laboratory study examined the influence of total aggregate gradation on the freeze-thaw durability of concrete test specimens that employed a variety of sedimentary and igneous aggregates common in Wisconsin. Optimized gradations consisted of increased amounts of aggregate particles in the No. 4 to 16 sieve size range and decreased amounts of fines in the No. 50 to 200 size range. A near-gap gradation was fabricated by removing some particles in the No. 4 to 16 size range and increasing the amount of fine material in the No. 30 to 100 size range. A control gradation utilized a 60-40 blend of coarse/fine aggregate with gradations determined by the naturally-occurring particle sizes. The concrete specimens prepared in this study were subject to strength, shrinkage, permeability and accelerated-freeze-thaw testing. All concretes had well-controlled water-cement ratios and showed excellent freeze-thaw durability. Conclusions: Although we considered a variety of methods for optimizing gradations in the context of practical constraints to enable field application, we did not identify an optimized gradation that provided a consistent benefit compared to the naturally occurring control gradations over all performance measures. The near-gap concrete tended to perform measurably worse than comparable control and optimized gradation concrete. Compressive strengths, shrinkages, and permeabilities were worse in near-gap concrete by single or double-digit percentages compared to the control mixes. Although in some cases, differences were very small, in all cases, the near-gap mixes showed the lowest freeze-thaw durabilities.

Steven M. Cramer, Ph.D., P.E., and Andrea Carpenter, Professor of Civil & Environmental Engineering and former Graduate Assistant, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706, Tel: (608)262-7711, Fax: (608)265-8213, email: cramer@engr.wisc.edu.

991176 "Proposed Guidelines for the Prevention of Alkali-Aggregate Reactivity in New Concrete Structures"

Abstract: A new approach is presented that is currently being considered by the Canadian Standards Association (CSA) Technical Group on Alkali-Aggregate Reaction (AAR) for the prevention of the risk of deterioration associated with the use of potentially reactive aggregates in concrete. This approach involves a risk evaluation process based on the following factors that are considered critical for the development of damage in concrete structures due to ASR: (1), the degree of reactivity of the particular reactive aggregate to counteract (i.e. non reactive, moderately reactive and highly reactive), (2), the exposure conditions to which a concrete elements will be exposed in the field (i.e. thin element in a dry environment, massive element in a dry environment, and any concrete element exposed to humid air, buried or immersed), and (3), the expected service life of the structures (i.e. temporary (< 5 years), service life from 5 to 50 years, and service life > 50 years). The proposed preventive actions against AAR will depend on the actual risk level thus determined (i.e. 1 (no risk) to 4 (high)), and will involve one or a combination of the following approaches: (1), reject the proposed aggregate, or use (1) or (2) below, (2), limit the alkali content of the opc concrete to specified values (the specified alkali content decreases with increasing preventive level), (3), use a sufficient amount of an effective supplementary cementing material (SCM), or combination of effective SCMs (minimum replacement levels are suggested as a function of the preventive level required).

Benoit Fournier, Ph.D., Research Scientist, CANMET, Department of Natural Resources Canada, 405 Rochester Street, Ottawa, Canada, K1A 0G1, Tel: (613) 992 8394 Fax: (613) 992 9389 email: bfournie@nrcan.gc.ca.

991190 "Field Installation in Pennsylvania to Assess SHRP Recommendations for ASR Control"

Abstract: At the close of the Strategic Highway Research Program (SHRP), several specific suggestions were made in regard to the prevention of alkali-silica reacitvity (ASR) in new concrete. One recommendation was that additional research on the field performance of highway structures should be performed. Another was that agencies should consider the addition of LiOH.H2O as a means of preventing ASR in new concrete. In May of 1997, the Pennsylvania Department of Transportation placed a test section of pavement on the Lackawanna Valley Industrial Highway (LVIH) in order to test some of the recomendations from SHRP regarding the prevention of ASR in new concrete. In addition to a control section which contained high alkali cement and highly reactive coarse and fine aggregates, eleven other sections were placed, most of which contained the same high alkali cement, the same reactive aggregates, and different proportions of Class F fly ash, ground granulated blast furnace slag, and/or LiOH.H2O. One of the eleven sections contained low alkali cement. The follow-up monitoring program for this ASR pavement test section is described. In addition, there is a laboratory testing program for the materials utilized on the job, which is intended to help correlate laboratory test results with field test results. The various laboratory test results planned by both PaDOT and The Portland Cement Association are outlined, as well. Conclusions: Although difficult, the placement of an ASR test pavement which incorporates varying percentages of ground granulated blast furnace slag, Class F fly ash, and other admixtures for ASR remediation can be accomplished without the use of high range water reducers.

Margaret C. Thomson, PG, Senior Civil Engineer, Materials and Testing Division, Pennsylvania Department of Transportation, 1118 State Street, Harrisburg, PA 17120. Ph.: 717-787-1931; Fx.: 717-783-5955, Email: margaret_thomson@hotmail.com; and David B. Stokes, FMC Corp., Lithium Division, Highway 161, Box 795, Bessemer City, NC 28016. Ph.: 704-868-5492; Fx.: 704-868-5496, Email: david_stokes@fmc.com.

991311 "An Evaluation of Concrete Flatwork Durability Problems in Minnesota"

Abstract: A high number of exterior concrete flatwork problems were reported in Minnesota following the winter of 1996-97. A panel was assembled to examine and test hardened concrete samples, analyze the resulting data, and develop recommendations for improving the quality of future concrete construction in Minnesota. Some panel members also contributed data from their own in-house studies of similar problems. The controllable factors that appear to have contributed to the premature deterioration of the greatest number of study projects include: the use of aggregate containing nondurable particles; high water-cementitious ratios, low cementitious contents; long transit times; mix retempering; finishing problems; inadequate curing; and late season paving. In addition, the large number of freeze-thaw cycles experienced during the winter of 1996-97 probably acted to accelerate the onset of the observed distresses. There was no evidence that the cement used in any of the projects was inferior, although there is evidence that cement brand can strongly influence air entrainment. Conclusions: It was often impossible to point to a single factor as the source of distress on any given project, and it could not be said that any one factor was primarily responsible for all of the problems observed. However, there was not an increase in durability-related distresses on Minnesota highway paving projects following the winter of 1996-97. This was attributed to differences in mix design (lower w/(c+p)), finishing and curing. Test results indicate that the most effective way to minimize scaling is to limit w/(c+p) to 0.45 or less. Burlene curing was also effective in reducing scaling severity. The report findings lead to a series of recommendations for suppliers, contractors and operators. Some of these recommendations may already be standard practice for certain suppliers, operators and contractors, and many simply advocate the adoption of what has always been considered good practice.

Mark B. Snyder, Ph.D., P.E., Associate Professor, University of Minnesota Department of Civil Engineering, 500 Pillsbury Drive SE, Minneapolis, MN 55455-0220, Tel: (612)-626-7843 Fax: (612)-626-7750, Email: mbsnyder@tc.umn.edu.

 

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VII. MINERAL AGGREGATES

990325 "Tests for Evaluating Fine Aggregate Particle Shape, Angularity and Surface Texture"

Abstract: Particle shape, angularity and surface texture are critical properties in assessing fine aggregate quality for asphalt concrete. The index for aggregate particle shape and texture, and uncompacted voids tests indirectly measure these properties. Several sources of fine aggregate from Alabama are evaluated with both tests. Modifications are suggested to current test procedures to include all particle sizes normally considered fine aggregate. Particle index and uncompacted voids are affected by gradation, and this effect should be eliminated in assessing fine aggregate quality. Testing individual size fractions and computing composite indexes or void contents, or testing samples with standard gradations are viable options for eliminating gradation effects. Particle indexes or uncompacted voids of blends of two aggregates may be assessed by linear proportioning of individual component values. Conclusions: Uncompacted voids are influenced by the size particles tested. The general trend is that smaller particle sizes have higher UV. This effect is not so prominent on particle index. Gradation affects measured voids and, therefore, also particle index. Testing individual size fractions and computing values for graded samples eliminates this effect and provides reasonable assessments of aggregate particle shape, angularity, and surface texture. Standard gradations may be used if they approximate actual gradations. The uncompacted voids and index of particle shape and texture tests provide comparable measures of fine aggregate quality. During the aggregate selection portion of mix design, UV for blends may be reasonably estimated with source UVs and linear proportions. However, after a blend is selected, material from each source should be combined in appropriate percentages and the composite sample broken down into required individual size fractions for testing. A weighted UV should be computed based on blend gradation.

M. Shabbir Hossain, Frazier Parker, Jr. and Prithvi S. Kandhal. Auburn University, Auburn,

AL 36849, Tel.: (334)-844-6284, Fax: (334)-844-6290, Email: fparker@eng.auburn.edu

991070 "Evaluation of Constructing Increased Single-Lift Thicknesses of Unbound Aggregate Bases: A Case Study in Georgia"

Abstract: A study was conducted to evaluate the feasibility of compacting unbound aggregate base courses in thicker lifts than currently permitted by state departments of transportation (DOTs). Most DOTs allow a maximum thickness of 8 in. (20.3 cm) or less. This project describes work conducted in conjunction with the widening of a state road in Georgia. Three test pads of the same material were constructed and evaluated: one Target Strip and two Test Sections. The Target Strip was placed in two lifts: a 7-in. (17.8-cm) lift followed by a 6-in. (15.2-cm) lift. Each Test Section was constructed in a single, 13-in. (33-cm) lift. Compaction was evaluated by a Nuclear Density Gage (NDG). Additionally, nondestructive seismic testing was used to evaluate base and subgrade stiffness profiles using the Spectral-Analysis-of-Surface-Waves (SASW) technique. Conclusions: NDG and SASW results show that a 13-in. (33 cm) thick layer can be compacted as dense and as stiff as a 6-in. (15-cm) layer. Measured stiffnesses results for the upper 3 in. (7.6 cm) are less than for the bottom 10 in. (25.4 cm). This is due to lower effective stresses and possible disturbance during compaction. Higher compaction moisture contents yield lower stiffnesses with negligible effect on density. Results indicate that thick (13-in. (33 cm)) single lifts can provide stiffness and density profiles equal to, or better than, those for two thinner lifts. The construction decision (lift thickness and moisture control) becomes somewhat subjective and depends on the contractor's judgement as to the construction effort required. Given adequate compaction equipment, the decision can depend primarily on which procedure requires the least time and equipment operations.

Kenneth Stokoe, II, University of Texas at Austin, Department of Civil Engineering, Austin, TX 78712, Tel: (512) 471-4929, Fax: (412) 471-6548, Email: k.stokoe@mail.utexas.edu.

991224 "Precision Of Flat And Elongated Particle Tests: ASTM 4791 And VDG-40 Videograder"

Abstract: The design procedures for Superpave and stone-matrix asphalt mixtures emphasize the importance of aggregate shape. The current test procedure for characterizing aggregate shape, ASTM D 4791, lacks a precision statement and is extremely time-consuming. A round robin was conducted with 15 laboratories, five materials, and two replicates to determine a precision statement for ASTM D 4791. The results from the round robin, and two additional materials, were compared with a promising automated device for measuring aggregate shape: the VDG-40 videograder. Although a correlation was indicated, further research is needed to relate the measurements of aggregate shape using both tests to hot-mix asphalt performance. Conclusions: Measurements made with ASTM D 4791 using the 2:1, 3:1 and 5:1 ratios are highly variable. The VDG-40 videograder indicates particle shape, and a correlation with ASTM D 4791 was determined (R2 = 69%). Preliminary work indicates very good repeatability for the VDG-40. Recommendations are made to continue research to relate aggregate shape measurement by either method with performance.

Brian D. Prowell, Senior Research Scientist, Virginia Transportation Research Council, 530 Edgemont Road, Charlottesville, VA 22903, (804) 293-1919, Fax (804) 293-1990, Email: bdp6q@virginia.edu; and Randy Weingart, Director of Quality and Product Research, Luck Stone Corporation, P.O. Box 29682, Richmond, VA 23242-0682, (804) 784-6345, Fax (804) 784-4781, Email: luckqc@access.digex.net.

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VIII. PAVEMENT MANAGEMENT, DESIGN AND PERFORMANCE

990010 "Rubblization Of Concrete Pavements"

Abstract: The Florida Department of Transportation (FDOT) is in the process of evaluating rubblizing concrete pavements as an effective rehabilitation technique in eliminating reflected cracks in asphalt overlays on top of concrete pavements. As part of that evaluation, a nationwide survey was performed to gather information about the practices of other DOTs with regard to rubblization and to determine the overall performance of rubblized sections in various states. This paper describes the findings of the survey. Conclusions: The survey indicated that most states have a relatively small number of rubblized sections with the exceptions of three states that have over ten sections each. AASHTO is the most widely used design procedure by state DOTs. The layer coefficient of the rubblized layer varied between 0.1 and 0.3. Most states require the majority of rubblized concrete particles to be 25.4 - 76.2 mm (1"-3") in size. The construction techniques, overlay thickness, and field performance varied significantly from state to state. However, it was clear that almost all states are highly satisfied with rubblization as a good mean for eliminating reflected cracks. Only a few states indicated problems with rubblization due to mainly weak subgrade.

Khaled Ksaibati, University of Wyoming, PO Box 3295, Laramie, WY 82071-3295, 307-766-6230, Fax: 307-766-2221, khaled@uwyo.edu.

990105 "Experimental Verification of Rigid Pavement Joint Load Transfer Modeling with EverFE"

Abstract: In this study, the joint load transfer modeling capabilities of EverFE, a recently developed rigid pavement 3D finite element analysis tool, are verified through comparisons with existing experimental data. Dowel joint load transfer is examined via comparison of displacements predicted by EverFE with results from laboratory tests of two small-scale doweled pavement systems, and dowel looseness is shown to be a probable cause for experimentally observed discrepancies in joint displacements. Results of finite element analyses using EverFE's nonlinear, two-phase aggregate interlock constitutive model are shown to agree well with available experimental data. A parametric study is performed that examines the effect of joint opening on aggregate interlock load transfer, and illustrates the importance of considering nonlinearities in joint load transfer when predicting pavement response. Recommendations for future research on joint load transfer modeling are also discussed. Conclusions: Using EverFE, dowel looseness is shown to be a probable cause of the differential vertical joint displacements observed in small-scale experimental tests of concrete pavements. Further comparisons with available experimental data indicate that EverFE's two-phase aggregate interlock model captures variations in joint load transfer with joint opening with reasonable accuracy. The importance of modeling nonlinear joint load transfer is underscored with a parametric study on the effect of joint opening on pavement response. Future research issues are also identified, including the need for mechanistic predictive models of joint load transfer degradation and controlled laboratory studies under high-cycle, low stress conditions.

Bill Davids, Department of Civil and Environmental Engineering, University of Maine, 5711 Boardman Hall, Orono, ME 04469-5711, Tel: (207) 581-2116, Fax: (207) 581-3888 Email: wdavids@umeciv.maine.edu; Joe P. Mahoney, Department of Civil Engineering, University of Washington, 121 More Hall, Seattle, WA 98195, Tel: (206) 685-1760 Fax: (206) 543-1543 Email: jmahoney@u.washington.edu.

990211 "Overview of Hot In-Place Recycling of Bituminous Pavements"

Abstract: A general definition of hot in-place recycling (HIPR) is provided. The three basic types of HIPR including multiple-pass and single-pass operations are briefly described and their benefits and shortcomings are discussed. Reasons for using HIPR as a tool for rehabilitation of asphalt pavements along with its limitations are summarized. The types of pavements that are suitable candidates for HIPR are addressed. Significant results from a telephone survey, conducted in 1992 to determine the extent of HIPR use by state DOTs, are discussed. Current HIPR asphalt mixture design philosophy and procedures for are summarized. The need for uniform mixture design procedures, construction specifications, and construction guidelines are indicated. Performance of HIPR pavements relative to conventional new overlays discussed in terms of correcting pavement surface distress, serviceability, structural value, comparative cost, and energy savings. The paper points out that considerable research is needed to furnish the paving industry with appropriate mixture design procedures (particularly with regard to sample curing), materials and construction specifications, general construction guidelines. Conclusions: The source of any problems must be corrected before or during HIPR or the problem will reoccur. A proper candidate for HIPR must be structurally sound. Strength equivalencies for pavement design are essentially equal to those of conventional mixtures. Failure to test viscosity of recovered binder from the recycled mixture may permit premature hardening of the asphalt. Sometimes it is difficult to add enough rejuvenator without overasphalting the mixture. The ideal candidate for HIPR is a pavement where the existing asphalt can be rejuvenated to its original, as-placed consistency. Two or three seal coats at the surface may cause the HIPR material to smoke and even catch fire. Seal coats act as insulation that prevents heat penetration. None of the HIPR methods currently in use are designed to provide major corrections in grade.

Joe W. Button, Texas Transportation Institute, Texas A&M University, College Station, Texas 77843-3135, Tel: 409/845-9965 Fax: 409/845-0278 Email: J-Button@tamu.edu; Cindy Estakhri, Texas Transportation Institute, Texas A&M University, College Station, Texas 77843-3135, Tel: 409/845-9551 Fax: 409/845-0278 Email: C-Estakhri@tamu.edu; Dallas N. Little, Texas Transportation Institute, Texas A&M University, College Station, Texas 77843-3135, Tel: 409/845-9963 Fax: 409/845-0278 Email: D-Little@tamu.edu.

990251 "Experimental Cold In-Place Recycling With Hydrated Lime"

Abstract: The Kansas Department of Transportation (KDOT) cold in-place recycles (CIR) approximately 120 to 160 km of pavement a year as a part of their 1-R maintenance program. Originally KDOT utilized asphalt emulsions as the additive in CIR mixtures but based on performance concerns currently utilize type C fly ash. Recent research indicates that the use of CIR with asphalt emulsion and hydrated lime, introduced as hot slurry, provides improved performance. KDOT constructed two test sections on US-283 using type C fly ash and CSS-1 with hot lime slurry. Samples of the materials were obtained and laboratory evaluations undertaken to evaluate the performance of CIR with hot lime slurry. Two additional mixing grade asphalt emulsions were evaluated as well, CMS-1 and HFE-150. Laboratory samples were tested for tensile strength, moisture sensitivity and resilient modulus. Laboratory compacted samples were tested for rutting resistance and moisture damage using the Asphalt Pavement Analyzer (Georgia Rut Tester). Results indicate that the use of hot lime slurry resulted in an improvement in material properties that affect the performance of CIR pavements, regardless of the emulsion used, and that CIR with hot lime slurry could be an alternative to the use of type C fly ash. Conclusions: The use of HLS resulted in increased unit weight, increased tensile strength, increased conditioned tensile strength, and increased resilient and conditioned resilient modulus, regardless of the AE. The APA testing showed that the use of HLS resulted in decreased wet and dry rut depths. The effectiveness of HLS in reducing the wet rut depths was much better with CMS-1 and CSS-1 than HFE-150 mixtures.

Stephen A. Cross, 2006 Learned Hall, Civil & Environmental Engineering Department, University of Kansas, Lawrence, Kansas 66045, Tel: (785) 864-4290, Fax: (785) 864-3199, Email: sac@kuhub.cc.ukans.edu.

990260 "Structural Coefficients for Fractured Concrete Slabs"

Abstract: A study was conducted to recommend appropriate ranges of structural coefficient values for fractured (rubblized, crack and seat, and break and seat) concrete slabs, for use in the AASHTO method of overlay design. The major activities conducted for this study were a review of the structural coefficient concept, a review of existing recommendations for structural coefficients for fractured slabs, and development of recommendations for ranges of structural coefficients for fractured slabs, for use with the current AASHTO overlay design procedure. The Structural Number by which flexible pavements are characterized in the AASHTO design procedure is a linear model in which the contribution of each layer above the subgrade is weighted by a structural coefficient. Despite evidence of nonlinearity of layer effects in the original AASHO Road Test data, and similar findings of several research studies in the decades after the AASHO Road Test, the Structural Number model is still used for flexible pavement design in the AASHTO Guide. The Guide also recommends that asphalt overlays of all types of fractured concrete slabs—rubblized, crack and seat, and break and seat—be designed using the Structural Number model. This paper describes the development of an appropriate range for the structural coefficient of fractured concrete, taking into consideration the performance of rubblized, crack and seat, and break and seat projects, compared to that of (a) conventional flexible pavements and (b) conventional asphalt overlays of intact concrete slabs; and presents a range of structural coefficients which produces reasonable overlay thicknesses for fractured slabs from either the rigid or flexible pavement design perspective. Conclusions: On the basis of the analyses done for this study, a range of 0.15 to 0.25, with a midrange value of 0.20, is recommended for use in the current AASHTO method for design of asphalt overlays for all three types of fractured concrete. For a given design serviceability loss, values at the low end of this range are more appropriate for larger future thickness requirements, while values at the high end of this range are more appropriate for smaller future thickness requirements. Structural coefficient values within the recommended range will yield asphalt overlay thicknesses for fractured concrete slabs which are consistent with both the rigid model and flexible model approaches to overlay design in the current AASHTO methodology. Nevertheless, both the structural coefficient concept and the structural deficiency approach to overlay design are areas, among many, in which the AASHTO methodology is clearly in need of improvement.

Kathleen T. Hall, Proyekta Ingeniería Ltda., Avenida Libertador Bernardo O'Higgins 1977, Oficina 32, Santiago, Chile, phone/fax 56-2-696-9906. US address: 1174 Beech Lane, Highland Park, IL 60035, phone/fax 847-433-2994. email: kthall@wwa.com

990339 "Performance of Bonded Concrete Overlays"

Abstract: A bonded concrete overlay (BCO) is a concrete pavement rehabilitation method used to extend the life of an existing concrete pavement. The BCO should bond fully with the existing concrete, leading to a thicker composite pavement section, a much stiffer pavement, and a considerable decrease in pavement stresses. For one project, cost estimates for a BCO were half as much as for full-depth replacement of a pavement. In some cases BCOs have debonded shortly after construction. If this occurs, the design assumptions are violated and the increase in pavement life may not be achieved. This paper discusses some of the causes of early age debonding in BCOs. The early age behavior of newly constructed BCOs is examined. The factors affecting the long-term performance of the BCO include the quality of the surface preparation, the materials used in the BCO, and the curing of the BCO. Research conducted by the University of Texas at Austin has led to recommendations for quality control to ensure satisfactory performance. Weather monitoring during BCO construction is recommended to identify time periods when weather conditions threaten bond development, and construction should be halted. Some methods of detecting and mapping debonding are discussed. The recommendations are used to analyze case studies of BCO. The lessons learned are useful not only for investigating BCO performance but also for understanding and preparing BCO construction specifications. Conclusions: A BCO is a cost-effective and efficient method for rehabilitation of a concrete pavement, although the risks of debonding have made some agencies reluctant to use them.

Norbert J. Delatte and John T. Laird, II, Department of Civil and Environmental Engineering, The University of Alabama at Birmingham, 1075 13th Street South, Suite 120, Birmingham, AL 35294-4440Telephone: (205) 934-8436, Fax: (205) 934-9855, Internet: ndelatte@eng.uab.edu and lairdj30@eng.uab.edu.

990409 "Ten Year Performance Review of In-Situ Hot Mix Recycling in Ontario"

Abstract: In today’s climate of environmental and economic constraints coupled with a diminishing aggregate supply, in-situ hot mix recycling provides an important alternative to conventional pavement rehabilitation. In-situ hot mix recycling, including hot in-place recycling (HIR) and cold in-place recycling (CIR), is proving to be an economical rehabilitation technique that conserves granular materials, energy, and results in zero waste. The Ministry of Transportation (MTO) and the Regional Municipality of Ottawa-Carleton (RMOC) have rehabilitated in excess of 80 projects utilizing in-situ hot mix recycling techniques since 1987. The HIR process is suitable for roadways exhibiting a variety of surficial non-structural distresses. CIR is suitable for roadways with moderate to severe distresses where reflection cracking is a concern. This paper provides an overview on the design, construction procedures, test results and pavement performance to date of in-situ recycling. Ten years of performance monitoring of the in-situ recycling projects has resulted in the evolution of design strategies and performance specifications. Their effectiveness, limitations, and future utility on highway contracts are also discussed in this paper. Conclusions: Overall the performance to date of the in-situ recycling processes has been comparable to pavements rehabilitated conventionally. In-situ recycling that uses 100% of the reclaimed asphalt product, shows potential to address the concerns of future zero waste environmentally conscious roadway rehabilitation contracts. Ongoing refinements in equipment and rejuvenator technology, evolution of mix design/specification requirements, incorporation of emission control systems, and improvements in field operations will ensure the long term performance of pavements rehabilitated using in-situ recycling technology.

Tom Kazmierowski, P.Eng., Manager, Pavements and Foundations Section, Ministry of Transportation, Ontario, Room 232, Central Building, 1201 Wilson Avenue, Downsview, ON M3M 1J8, Phone: (416) 235-3512, Fax: (416) 235-3919, Email: kazmiero@mto.gov.on.ca.

990627 "Structural Adequacy of Rubblized PCC Pavements"

Abstract: The objective of rubblization is to eliminate reflection cracking in HMA overlay by the total destruction of the existing slab action. Rubblization is applicable when there is little potential of retaining slab integrity and structural capacity of the original JRCP. It has also been used successfully for rehabilitation of other PCC pavement types. Typically, the slab is reduced into pieces less than 300mm in size. Subsequently, the slab is converted to a high-strength granular base. Restoration of the structural capacity is accomplished with an overlay of HMA. In 1991, INDOT awarded a contract to apply the rubblization technique to a portion of US-41 in Benton County, Indiana. The pavement sections were evaluated prior to and after rubblizing and overlay to estimate the AASHTO layer coefficient of rubblized concrete pavements. Conclusions: 1. Rubblizing appears to provide a uniform, stable/high-strength granular base/subbase for asphalt concrete overlays. 2. To ensure structural adequacy, a layer coefficient of 0.22 appears to be reasonable for rubblized PCC pavements with similar conditions. This layer coefficient is set within two standard deviation of the mean (mean = 0.25). 3. Rubblization appears to be a valid option for INDOT to use in the rehabilitation of PCC pavements. 4.If INDOT continues to use rubblization in the rehabilitation of PCC pavements, further studies are recommend. These studies should encompass slabs of different thicknesses on different subgrades. The effect of the rubblizing equipment should also be examined.

Khaled A. Galal, Brian J. Coree, John E. Haddock, and Thomas D. White, Indiana Department of Transportation - Division of Research, 1205 Montgomery Street, P.O. Box 2279, West Lafayette, Indiana 47906, Tel. (765) 463-1521 Ext. 253, Fax (765) 497-1665, Email: khaled_galal@hotmail.com

990693 "Westergaard Curling Solution Reconsidered"

Abstract: An in-depth and systematic examination is presented of the effect of temperature gradients on slab-on-grade pavements, whose main objective has been the development of practical design tools for use in a typical engineering office. This has been achieved by a critical reconsideration of the literature, a synthesis of currently available analytical resources, and the implementation of recent technological achievements promulgated in related areas of engineering. Prominent among these are the application of the principles of dimensional analysis, the finite element method (FEM), advanced statistical regression analysis, and artificial neural networks (ANN). A number of ANNs have been trained for the curling problem, and in several instances they are found to be more efficient predictive tools than corresponding statistical regression equations. Conclusions: It is found that the most important shortcomings of the Westergaard curling solution are his assumption of continuous contact between slab and subgrade (infinite slab self-weight), and his explicit treatment only of day-time conditions. Although Westergaard's curling-only predictions are significantly inferior to those from ANN and statistics, his load-plus-curling predictions exhibit approximately the same scatter as those from these two more modern and nominally more sophisticated tools. The case of Westergaard's curling solution can serve as an example pointing to the usefulness and desirability of theoretical solutions, even when these are only achievable on the basis of considerable abstraction and simplification.

Anastasios M. Ioannides, Department of Civil and Environmental Engineering, University of Cincinnati (ML-0071), P.O. Box 210071, Cincinnati, OH 45221-0071, tel.: (513) 556-3137, fax: (513) 556-2599, Email: aioannid@boss.cee.uc.edu; Craig M. Davis, and Christopher M. Weber

990704 "Rehabilitation Performance Prediction Models For Concrete Pavements"

Abstract: Successful implementation of a pavement management system requires the necessary simulation tools, among which deterioration prediction models form an important part. These models can be either aggregate or incremental. Aggregate models calculate total accumulated deterioration, and require knowledge of the past history of the pavement in order to predict future behavior. Incremental models, on the other hand, only require a knowledge of the current pavement conditions. For this reason, incremental models are generally more advantageous when historical pavement condition data are not available. One of the most well known and widely used methods for pavement evaluation is the World Bank program HDM, whose latest version, HDM 4, attempts to accommodate the analysis of both asphalt and concrete pavements. In the case of concrete pavements, the models used are of the aggregate type. Incremental prediction models are used for asphalt pavements. As part of research into the application of incremental models for the prediction of distresses in concrete pavements, rehabilitation performance prediction models in incremental form have been developed and are presented in this paper. Rehabilitation performance refers to pavements that have already received repair or rehabilitation to enhance their structural or functional capabilities. The rehabilitation models presented here have been developed using mathematical combinations of models for new concrete pavements, derived as function of time. The results of validation analyses of the models are also presented, along with a discussion of the advantages and disadvantages of the proposed models with respect to existing methods. Conclusions: The main accomplishment of the research project on which this paper is based, was the development of the first incremental models for deterioration of rehabilitated jointed plain and jointed reinforced concrete pavements. This represents an important innovation in the development of deterioration models used for pavements management. A series of alternative models is presented, that provides a new and different approach to the prediction of concrete pavement deterioration. These incremental deterioration models offer important advantages, mostly for evaluation of pavements in service, because, as indicated many times before, they do not require historical background for the prediction.

Hernan De Solminihac T., Associate Professor, School of Engineering, Pontificia Universidad Católica de Chile. Casilla 306.Correo 22. Santiago, Chile, Tel (56-2) 686-4245, FAX (56-2) 686-4806, email: hsolmini@ing.puc.cl; Ricardo Salsilli M., Assistant Professor, School of Engineering, Universidad de Chile, Plaza Ercilla 883, Tel (56-2) 678-4177, FAX (56-2) 678-4142, email: rasm@cmet.net; Juan Pablo Covarrubias T., General Manager, Instituto Chileno del Cemento y del Hormigón, Pio X Providencia, Tel (56-2) 232-6777, FAX (56-2) 233-9765, email ichmail@ich.cl; and Mariana Vidal M., Research Engineer, School of Engineering. Pontificia Universidad Católica de Chile, Casilla 306.Correo 22, Santiago, Chile, Tel (56-2) 686-4245, FAX (56-2) 686-4806.

990731 "Field Performance Of CRCP In Illinois"

Abstract: This paper reviews the design and performance of continuously reinforced concrete pavement (CRCP) in Illinois. Illinois has built over 4,267 two-lane km (2,650 miles) of CRCP on the Interstate system since the mid-1950s. CRCP has been constructed on nearly all urban freeways in the Chicago area and has shown excellent performance under sever weather and heavy traffic conditions. The effect of key design and construction parameters on long-term CRCP performance is investigated using a database that was compiled based on field surveys conducted from 1977 to 1994 by the Illinois Department of Transportation (IDOT). Conclusions: Analysis of the data shows the following variables have significant effects on performance: longitudinal reinforcement content (greatest effect of all variables), slab thickness (also very significant), traffic load applications, depth of reinforcement, base type, and D-cracking of concrete. CRCP built with tubes or chairs exhibited overall about the same performance. Experimental field studies in Illinois showed that depth of reinforcement has a large effect on crack width and, eventually, on punchouts. Specifically, the investigation indicated that CRCP sections with a slab 178 mm (7 in) thick and steel content less than 0.6 percent developed the most structural failures. CRCP sections with a slab 254 mm (10 in) thick and steel content from 0.7 to 0.8 percent developed the fewest failures. However, all the CRCP sections in this study, regardless of thickness designs and steel content, have typically carried more traffic than they were designed for and have lasted longer than their design traffic life.

Nasir G. Gharaibeh, ERES Consultants, Inc., 505 West University Avenue, Champaign, IL 61820, Tel: (217)356-4500, Fax: (217)356-3088, Email: ngharaibeh@eresnet.com; Michael I. Darter, ERES Consultants, Inc., 505 West University Avenue, Champaign, IL 61820, Tel: (217)356-4500, Fax: (217)356-3088, Email: mdarter@eresnet.com; Laura B. Heckel, Illinois Department of Transportation, 126 East Ash Street, Springfield, IL, 62704, Tel (217) 782-8582, Fax: (217) 782-2572, Email: HeckelLB@nt.dot.state.il.us.

990878 "Mechanistic Reappraisal of the Current Design Methodology for Rigid Airfield Pavements"

Abstract: The main objective of this study is to reevaluate the current design methodology for rigid airfield pavements in attempts to accommodate the new-coming Boeing 777 airplanes based on the plate theory approach. The differences of the conventional FAA design method and the newly developed LEDFAA design methodology are investigated. The original concept of pass-to-coverage ratio is reevaluated. The prediction models developed by Lee, et al. (1997) are utilized for the estimation of critical edge stresses for design. The problems and difficulties of the conventional method especially in the conversions of different aircraft types are identified. The concept of cumulative damage factor should be used to account for the combined damages of different aircraft types and departures. Structural deterioration relationships are compared and tentative modification alternatives are explored. Consequently, the concept of an equivalent stress factor is introduced and an alternative structural deterioration model is proposed for trial design applications. Further investigations and verifications should be conducted as well. Conclusions: The "unduly conservative" aspect of the present design methodology when analyzing the main gear assembly of B-777 airplanes is probably tied to the manner in which critical tensile stress was determined. The well recognized effect of stress reduction due to the wandering of the centerline location of the lateral wheel load placement (Lc), moving away from the maximum tensile stress location, is totally neglected by the use of P/C concept. Thus, the Corps of Engineers accelerated traffic data provided by Gucbilmez and Yuce (1995) was reanalyzed. An equivalent stress factor (f3) based on the equivalency of the cumulative fatigue damages to account for the lateral wandering effect of the Lc within the full tire print area is introduced. An alternative structural deterioration relationship is obtained. Continuous research effort is underway to implement the proposed approach into a user-friendly computer program.

Ying-Haur Lee, Department of Civil Engineering, Tamkang University, E725, #151, Ying-Chuan Rd., Tamsui, Taipei, Taiwan 251, Republic of China; Tel: (886-2) 2623-2408, Fax: (886-2) 2620-9747, Email: yinghaur@mail.tku.edu.tw.

990922 "Hot Mix Asphalt Overlay Design Concepts For Rubblized PCC Pavements"

Abstract: The Illinois Department of Transportation's (IDOT) first interstate concrete rubblization project (150-mm and 200-mm Hot Mix Asphalt Overlays [HMA OL]) was constructed in 1990 on I-57 near Pesotum, IL as part of the SHRP LTPP SPS-6 PCCP rehabilitation study. The Pesotum sections have provided excellent performance and have accomodated approximately 7.5 million ESALs through 1998. Three additional IDOT Interstate rubblized PCCP projects have been constructed since 1990. IDOT utilizes Mechanistic-Empirical (M-E) flexible pavement design procedures for full-depth asphalt and conventional flexible pavements. HMA OL fatigue considerations control the HMA OL thickness requirement for rubblized PCCPs. Pesotum FWD data and HMA OL fatigue performance information are utilized in the initial development of the two M-E based HMA OL design procedures described in this paper. Results from the other three Rubblized PCCP projects are used to refine and validate the M-E design concepts. In the design procedures, the HMA OL tensile strain and a HMA strain-based fatigue algorithm are used to consider fatigue. An FWD deflection basin parameter (AUPP [Area Under Pavement Profile]) is used to estimate the HMA OL tensile strain. Thus, AUPP data for HMA OLs over rubblized PCCPs can be used to estimate HMA strain without utilizing backcalculation and structural modelling procedures. FWD data for the IL projects indicate AUPP can be estimated from ET3 (E - HMA modulus; T - HMA OL thickness]. As ET3 increases, AUPP and HMA strain decrease (increased HMA fatigue life). Conclusion: Two M-E based procedures are presented. One procedure estimates the HMA OL fatigue life from a HMA strain-based fatigue algorithm. An alternative approach is to extrapolate the HMA OL performance of existing rubblized PCCP pavements to new design conditions (differing Es and Ts).

Marshall R. Thompson, University of Illinois, 205 North Mathews, Urbana, IL 61801-2352, PH: 217-333-3930, FAX: 217-333-1924, Email: mrthomps@uiuc.edu.

990936 "Cost-Effective Rehabilitation of Portland Cement Concrete Pavement in Nevada"

Abstract: The purpose of this research, was to evaluate the feasibility of several

rehabilitation strategies for Portland Cement Concrete (PCC) pavement. Recommendations were made for future rubblization, crack and seat, and reconstruction projects based on a review of specifications from several other states, the data gathered during the Interstate 80 project, the experience gained during the construction phase of the project, and review of several overlay design procedures. The results of the study, based on 4 years of field performance, indicate rubblization, crack and seat, and reconstruction techniques are all viable options. The economic analysis indicates crack and seat has the lowest initial cost. However, based on projected future performance, both rubblization and crack and seat have approximately the same life-cycle cost over a 35 year analysis period. Pavement performance monitoring is continuing in order to evaluate long term performance and cost-effectiveness of each strategy. Conclusions: The functional and structural performance of the pavements indicate both the cracked and seated and rubblized sections are performing equally well. The ride quality, rut depths, and structural capacities of both techniques are still rated within the good to excellent range. Rubblization and crack and seat are effective methods for delaying reflective cracking if designed and constructed properly. However, their long-term performance in Nevada must still be analyzed. Empirical design procedures should be used to determine the initial overlay thickness. However, deflection measurements should be taken after the project is completed in order to verify the design assumptions. Structural coefficient values should be adjusted accordingly based on the deflection values.

Sohila Bemanian, Principal Materials Engineer, Nevada Department of Transportation,

1263 S. Stewart Street, Carson City, NV 89712, Tel: (702) 888-7520 Fax: (702) 888-7501, Email: h9026sll@dot.state.nv.us.

991016 "Ten Year Evaluation of a Concrete Pavement Rehabilitation Project in Ontario"

Abstract: In the summer of 1989, the Ministry of Transportation of Ontario (MTO) undertook the rehabilitation of an exposed concrete pavement exhibiting various distress manifestations. Highway 126 in Southwestern Ontario is a four-lane divided arterial with 25,000 AADT and 15% commercial traffic. The existing pavement constructed in 1963, consisted of 230 mm mesh reinforced Portland Cement Concrete pavement with doweled joints at a spacing of 21.3 m. The rehabilitation of the highway in the northbound lanes consisted of using the latest developments in Portland Cement Concrete (PCC) rehabilitation design techniques, material specifications and construction methods. The rehabilitation techniques included full depth repair, partial depth repair, diamond grinding, and joint sealant replacement on the northbound lanes which had experienced moderate deterioration. The southbound lanes received a 180 mm thick plain jointed unbonded PCC overlay to address the severe ‘D’ cracking and spalling at all the joints and cracks. This paper will discuss the ten year evaluation of this rehabilitated pavement in terms of roughness measurements using the Portable Universal Roughness Device, frictional resistance measured with the ASTM brake-force trailer, Pavement Condition Ratings and crack surveys. Also include will be a discussion on subsequent localized concrete pavement repair work completed on the highway during the ten years. Conclusions: Monitoring the performance of the pavement over the last nine years has indicated that locations for partial depth repairs must be chosen judiciously to ensure that they are not greater than one-third of the slab depth. Where existing pavement joints have seized and full depth repairs are constructed at mid-slab further deterioration of secondary minor transverse cracks can occur, consideration should be given to carrying out full depth repairs at these locations during initial construction. Although diamond grinding significantly improved the ride of the rehabilitated pavement, the initial improvement in skid resistance has dissipated so that after nine years it is 10 units lower that the burlap dragged/tined surface. The nine year performance of the unbonded 180 mm thick overlay has been excellent with good ride quality and skid resistance and no reflection cracking.

T. J. Kazmierowski P.Eng., Manager, Pavements and Foundations Section,

Tel: (416) 235-3512, Fax: (416) 235-3919, Email: kazmiero@mto.gov.on.ca; and Alison Bradbury P.Eng., Senior Pavement Design Engineer, Pavements and Foundations Section, Tel: (416) 235-3513, Fax: (416) 235-3919, Email: bradbury@mto.gov.on.ca, Ministry of Transportation, Ontario, Room 232, Central Building, 1201 Wilson Ave., Toronto, Ontario, Canada, M3M 1J8.

991209 "The Full Depth Reclamation Process"

Abstract: Today’s increased traffic volumes and wheel loadings have caused many roads and streets to fail structurally because of inadequate roadbase strength. For this reason, public agencies throughout the world are making full depth reclamation (FDR) one of the most popular pavement rehabilitation methods. The FDR process allows complete reconstruction utilizing 100 percent of the existing pavement materials, while correcting grade, cross-slope, and underlying pavement problems at the same time. In FDR, a new base is produced by pulverizing the existing asphalt pavement and mixing it with some of the underlying granular materials. Additional structural strength can be achieved by incorporating new crushed aggregates, asphalt emulsion, foamed asphalt and chemical stabilizers such as Portland Cement, fly ash, hydrated lime, and calcium chloride or a combination of these and other specialized additives. Lab testing of the reclaimed asphalt pavement (RAP), the subgrade soils and a mixture of the two will dictate whether an additive is needed and the type and amount to be applied. A thorough project evaluation including a pavement condition survey, traffic study, and structural design is essential to assure success. Finally, proper construction procedures and quality control plus an experienced contractor are necessary. Conclusions: FDR is an environmentally sound, cost effective and long lasting pavement rehabilitation treatment. Since it is completed in-place with existing pavement materials, energy and natural resources are conserved.

Edward J. Kearney, PE , Gorman Brothers Inc,Church St, Port of Albany, Albany, NY 12202 Tel: (518) 462-5401 Fax: (518) 462-1296; John E. Huffman, PE , Brown & Brown Inc , PO Box 2000, Salina, KS 67402-2000 Tel: (785) 827-4439, Fax (785) 825-2457, Email browninc@midusa.net.

991220 "Longevity of Diamond-Ground Concrete Pavements"

Abstract: Diamond grinding restores a smooth riding surface with the desirable friction characteristics on concrete pavements. This technique was first used in 1965 on a 19-year-old section of I-10 in southern California to eliminate excessive faulting. Since then, diamond grinding has become a major element of concrete pavement restoration (CPR) projects. Despite this long history, very little valid documentation of the performance of diamond-ground pavements exists. In recognition of the critical need for such information, the Portland Cement Association (PCA), in association with American Concrete Pavement Association (ACPA) and International Grooving and Grinding Association (IGGA), sponsored a study of performance of diamond-ground pavements. The study involved conducting a comprehensive review of existing information on diamond grinding, data collection, data analysis, and documentation of the study findings. Extensive field surveys were conducted to obtain the performance data needed for the analysis. In all, 60 pavement sections in 18 States were surveyed. In addition, performance data for 133 sections were obtained from an earlier study of the performance of diamond-ground pavements. The LTPP database was also used because the SPS-6 sections (CPR) provide opportunity for the direct, side-by-side comparison of the performance of diamond-ground pavement sections and other rehabilitation alternatives. Various analyses were conducted to document the performance of diamond-ground pavements, including an evaluation of faulting performance, longevity of diamond-ground texture, and the effects of diamond grinding on service life. This paper presents a brief description of the work conducted and a summary of the findings. Conclusions: The results of this study show that CPR with diamond grinding is an effective means of extending service life of concrete pavements.

Shreenath Rao, H.T. Yu, M.I. Darter, L. Khazanovich, and J.W. Mack, ERES Consultants, Inc., 505 W. University Ave., Champaign, IL 61820, Phone: (217)356-4500, Fax: (217)356-3088, Email: srao@eresnet.com.

991341: "Design and Construction Guidelines for Unbonded PCC Overlays"

Abstract: An effective method of rehabilitating PCC pavements is by resurfacing them with an unbonded PCC overlay. This type of overlay is a cost-effective method for increasing the structural strength of badly deteriorated existing pavements and provides a new surface with improved riding quality. Other advantages include its suitability for use without extensive repair of the existing pavement and an interlayer that minimizes the occurrence of reflective cracking. Also, no special techniques are necessary during construction and conventional paving methods and equipment can be used. In addition, conventional CPR techniques can be applied to improve performance during service. Because of these advantages an unbonded overlay is an attractive option for rehabilitation. However, there is a lack of guidance on the design features and construction practices for building long-lasting and cost-effective unbonded overlays. Consequently, several highway agencies often do not consider it as a viable rehabilitation option and are unfamiliar with its design and construction. To address this deficiency improved guidelines have been developed for the design, construction, and performance evaluation of unbonded overlays. The guidelines were developed from a review of current worldwide practice and the results of analytical investigations of many in-service unbonded overlays. The paper presents the findings of the study and provides a summary of the guidelines that can be used to design and construct long-lived unbonded concrete pavements. Conclusions: Unbonded concrete overlays are effective for restoring badly deteriorated concrete pavements for any level of future traffic. Some pavements evaluated carry as much as 3 million ESALs per year. However, the design procedures commonly used often provide insufficient thickness that can lead to early failures. Therefore, careful consideration of design features that enhance performance is critical. Guidelines are provided on preoverlay repair, interlayer properties and thickness, overlay thickness, joint spacing, joint load transfer, mismatching of joints, subdrainage, shoulders, reinforcement, and pavement widening.

E.B. Owusu-Antwi, Dept. of Civil & Environmental Engineering, Arizona State University, P.O. Box 875306, Tempe, AZ 85287, Tel: (602)965-0199, Fax: (602)965-0557, Email: Emmanuel.OwusuAntwi@asu.edu.

991389 "Lessons Learned: Performance of Utah’s Original I-15 Concrete Pavement in Salt Lake City"

This paper is not included on the 1999 Preprint CD-ROM. Please contact author for information.

Abstract: The jointed plain concrete pavements on Utah’s I-15 in Salt Lake City were constructed in the 1960s and represent Utah’s first concrete pavement on a major expressway. Over the past 33 years, this heavily trafficked section of I-15 has provided outstanding service and has required very little maintenance and rehabilitation. What makes this success story interesting is that some of the pavement’s design features are not what are thought of today as "best practices" in concrete pavement design. The use of narrow transverse joints, the omission of dowel bars at transverse joints, relatively thin slabs, and the use of large aggregates in the portland cement concrete mixes are not in line with current major highway practices; however, I-15 has performed remarkably, indicating that these nontraditional design features can work in some cases. Some critical factors, however, are in line with current best practices. This paper identifies the various design and construction parameters used in the original I-15 pavement and highlights those characteristics that have resulted in its exceptional performance. This paper is based on a detailed pavement investigation that was performed on I-15 in 1993 to identify future rehabilitation strategies. The results from this effort led to several of the design parameters for the new I-15 concrete pavement and provide valuable information for all concrete pavement designers and builders. Conclusions: This paper illustrates that the original jointed plain concrete pavements on Utah’s I-15 have provided outstanding service, while requiring very little maintenance and rehabilitation. Although many of the pavement’s design features are not what are thought of today as "best practices" in concrete pavement design, this pavement has performed remarkably. In 1993, the subject I-15 pavements had provided almost 30 years of service and accommodated over 20 million ESALs while experiencing minimal amounts cracking, spalling, pumping, and faulting. This high-performing, low-maintenance pavement has provided the Utah DOT and the traveling public a dual benefit. First, they reduced actual pavement maintenance costs, and second, they minimized the number of lane closures and associated users delays and costs. The reduction in user costs can be very significant in urban areas such as Salt Lake City. A summary of the key features and their associated effects are provided below. Design feature Effect Granular embankment beneath CTB Eliminated erosion and pumping beneath the CTB. Durable CTB that was bonded to JPCP for some time Bonding of CTB to JPCP resulted in a monolithic slab/CTB system that provided greater resistance to traffic loadings. The bonding also minimized the erosion between the CTB and the JPCP. Use of the CTB allowed for successful use of a relatively thin JPCP slab. Short transverse joint spacing Reduced curling and warping stresses in the JPCP. Narrow single joint sawcut Minimal spalling and reduce tire noise. Durable PCC No D-cracking or freeze-thaw damage. Large aggregates in PCC mixture Large coarse aggregates provide excellent aggregate interlock at the transverse joints. Adequate subdrainage for climate The underlying granular subbase and embankment provided "bottom" drainage and reduced erosion. This case study also highlights nontraditional design features such as the use of narrow transverse joints, the omission of dowel bars at transverse joints, and the use of large aggregate PCC mixes. Although these items are not commonly specified, they can work in some cases. In addition, this paper illustrates the potential benefits of short transverse joint spacing and a stabilized base. These items, when properly designed and constructed, can greatly enhance the performance of a JPCP.

Curt Beckemeyer, P.E., ERES Consultants, Inc., 505 W. University Avenue, Champaign, IL 61820, Tel. (217) 356-4500, Fax (217) 356-3088, Email: cbeckemeyer@eresnet.com; Michael Darter, Ph.D., P.E., ERES Consultants, Inc., 505 W. University Avenue, Champaign, IL 61820, Tel. (217) 356-4500, Fax (217) 356-3088, Email: mdarter@eresnet.com; and Wade Betenson, P.E., C.P.M., Engineer for Pavements, Utah Department of Transportation, 4501 South 2700 West, Salt Lake City, UT 84119, Tel. (801) 965-4303, Fax (801) 965-4796, Email: wbetenso@dot.state.ut.us.

991460 "Controlling Early-Age Cracking in Continuously Reinforced Concrete Pavement: Observations from 12 Years of Monitoring Experimental Test Sections in Houston, Texas"

Abstract: This paper presents findings drawn from twelve years of monitoring and analyzing thermal cracking in 85 experimental Continuously Reinforced Concrete (CRC) pavements placed in and around Houston between 1986 and 1995. Each of the eight projects consists of from 8 to 22 experimental sections of slightly different design. These sections were closely controlled and monitored during construction and periodically surveyed up until the present time. Adjacent placement of the experimental sections in each project minimized the effect of uncontrolled variables such as traffic and climate. The purpose of the study was to evaluate new design elements and construction considerations intended to control early-age thermal cracking and cracking-related distress caused by coarse aggregate with a high thermal coefficient of expansion. Experimental factors considered include coarse aggregate type, percentage of steel reinforcement, bar size, double or single mat steel, paving time, and paving season. Conclusions: Findings from the study show significant differences in performance between low and high thermal coefficient aggregates. Siliceous aggregates performed poorly in terms of number of closely spaced cracks (under 3 ft) compared to limestone. Pavements placed in winter performed significantly better than summer paving, especially when thermally expansive aggregates were used. Placing pavements at night proved only slightly better than daytime placement, probably because nighttime temperatures were still high in the early evening when construction occurred.. Decreased steel percentages resulted in better crack spacings but wider crack openings. Variations in steel bar size and skewed double-mat steel proved less significant in the long term. The use of blended aggregates, which showed promise in the lab, produced inconclusive results in the field study.

Terry Dossey, Center for Transportation Research, The University of Texas at Austin, 3208 Red River #200, Austin TX 78705, phone (512) 232-3124, fax (512) 232-3153, email Terry.Dossey@mail.utexas.edu; and B. Frank McCullough, Center for Transportation Research, The University of Texas at Austin, 3208 Red River #100, Austin TX 78705, phone (512) 232-3141, fax (512) 232-3151, email bfmcullough@mail.utexas.edu.

991462 "Considerations for High Performance Concrete Paving: Recommendations from 20 Years of Field Experience in Texas"

Abstract: This paper presents recommendations for High Performance Concrete Paving (HPCP) practice drawn from twenty years of designing and monitoring the performance of Continuously Reinforced Concrete (CRC) pavements in Texas. Performance indicators used include crack spacing distribution, crack width, crack randomness, delamination spalling, and vertical distribution of tensile strength. Variables studied include aggregate type (limestone or siliceous gravel), aggregate blending, placement season, placement time of day, placement above 90° F, use of crack initiators, use of skewed transverse steel, evaporation rate, percent steel reinforcement, and steel bar diameter. The variables studied are ranked in the order they affected performance in order to identify which are significant and can be controlled in the design and construction phases. The study utilized a diverse data pool from many Texas paving projects, primarily 85 CRC experimental pavements built between 1986 and 1995 in the Houston area. These sections were closely controlled and monitored from construction to the present time. The sections were carefully placed to minimize the effect of uncontrolled variables such as traffic and climate. Conclusions: Controlling concrete temperature and water loss are critical during hot weather placement of PCC; using thermally expansive aggregates compounds the problem. The critical air temperature for PCC paving was found to be 90 F; paving above this temperature with thermally expansive aggregates requires corrective measures such as cooling of aggregate stockpiles, adding ice, and/or the use of retarder to delay peak concrete hydration. The critical evaporation rate is 0.2 lb/ft2/hr; multiple coats of curing compound, the use of monomolecular film, or even polyethylene sheeting is recommended when evaporation exceeds this threshold. Weather stations, maturity meters, and other devices that indicate in-situ temperatures and evaporation rates identify dangerous conditions in time to take corrective measures and thus insure adequate performance. Failure to control early-age concrete temperature results in closely-spaced, uneven cracking leading to premature failure. Failure to control evaporation can result in plastic shrinkage cracking, poor vertical strength profile, and ultimately spalling.

Terry Dossey, Center for Transportation Research, The University of Texas at Austin, 3208 Red River #200, Austin TX 78705, phone (512) 232-3124, fax (512) 232-3153, email Terry.Dossey@mail.utexas.edu; and B. Frank McCullough, Center for Transportation Research, The University of Texas at Austin, 3208 Red River #100, Austin TX 78705, phone (512) 232-3141, fax (512) 232-3151, email bfmcullough@mail.utexas.edu.

991497 "Evaluation of Rigid Pavement Joint Seal Movement"

Abstract: The collection of rigid pavement joint movement data at sixteen seasonal LTTP sites provides the opportunity to assess the actual joint movements and evaluate these relative to current joint seal design practices. Evaluation of these joint movements relative to the ambient temperature range in different climates within the United States provides insight into the field performance of rigid pavement joints. From this basis, observations are made about the applicability of current joint seal design practices. A comparison of observed joint movement data with estimates calculated using the AASHTO equation for joint movement indicates that the current procedures are inadequate in estimating joint movement under most conditions. In addition, the observed data confirms the erratic movement of joints at all the sites reviewed. These occasional joints open significantly more than the normal movement observed for climatic conditions at each specific site. Correlations developed during this study may lead to a more accurate estimate of slab joint movement. The combination of the effect of temperature ranges, irregular joint opening, and the inaccuracy of currently used models for estimating joint openings explain major deficiencies in accomplishing effective joint sealing in the field. Conclusions: The inaccuracy of existing joint seal movement models may be responsible for failure of joint seals to perform as designed. Joints are not being effectively sealed, in general, since at all sites approximately one-third of joint openings are much larger than the average of the majority of joints. Further, average measured openings are greater than those for which joint sealants have historically been designed.

Dennis A. Morian, Quality Engineering Solutions, 670 Cartwright Rd., Reno, NV 89511, Tel: (702) 847-7703 Fax: (702) 847-7703, Email: morian@worldnet.att.net; Nadarajah Suthahar, Nichols Consulting Engineers, 1885 S. Arlington, Ave. Suite 111, Reno, NV 89509, Tel: (702) 329-4955 Fax: (702) 329-5098, Email: sutha@nce.reno.nv.us; and Shelley Stoffels, D.E., P.E., Pennsylvania State University, 212 Sackett Bldg., University Park, PA 16802, Tel: (814)865-4622 Fax: (814)863-7304, Email: stoffels@psu.edu.

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IX. ROADSIDE SAFETY

990037 "A New Method For Installing Break-Away Highway Signs"

Abstract: Highway signs require break-away base connections. These connections will

slip under impact, therefore preventing injuries to the occupants of an impacting vehicle. The break-away connection works as long as the tension of the bolts is maintained between an allowable range. A new method to insure that the bolts are tensioned to the proper value is presented. It is based on the use of Belleville spring washers. For each bolt diameter, a proper combinations of spring washers was selected and tested. The tension in the bolt is indirectly measured by measuring the deflection of the stack of spring washers during installation, with the help of filler gages. The tests show that the method is efficient and reliable. Conclusions: The method is fairly simple, and easy to implement. For each different bolt diameter and associated load range, a combination of spring washers is recommended. The stacks of spring washers are installed on the bolt just as any ordinary washers, and the bolts are torqued with any kind of torque wrench until the spring washers deflect a specified amount. The tension in the bolt is monitored by measuring the deflection of the stack of spring washers, with the help of a filler gage. This technique eliminates the uncertainties associated with torque measurements, and it provides a reliable way to estimate the tension of the bolt, as long as the initial point of zero deflections for the spring washers is correctly identified. This last point can be reasonably achieved by hand torquing the nut against the washers until they come into contact. The field tests carried out so far have confirmed that with spring washers the tension in the bolts is more likely to be and to remain in the allowable range. The installation procedure could be significantly improved, though, with the manufacturing of a specially designed filler gage adapted to the specific needs of the installation.

Jean-Paul Pinelli, Ph.D., P.E., Assistant Professor, Civil Engineering Program Chelakara S. Subramanian, Ph.D., P.E., Associate Professor, Aerospace Engineering Program Florida Tech, 150 W University Blvd, Tel: (407) 674-8085, Fax: (407) 674-7565.

990370 "Three-Cable Median Barrier Performance and Costs in Oregon"

Abstract: Oregon public interest peaked regarding crossover highway safety following three fatalities from a crossover accident in August of 1996. The Oregon Department of Transportation (ODOT) conducted a review of possible barrier solutions for the interstate highway median near Salem, Oregon. The weak-post three-cable median barrier system was selected. Unfortunately, there is not much information concerning the maintenance and repair costs of the cable barrier system. This study evaluates the effectiveness of the three-cable barrier in preventing crossover accidents on Interstate 5 (I-5), Oregon Highway Number 1, and evaluates the maintenance and repair costs in order to make recommendations for future installations. Based on the results of the study, the cable median barrier system proved to be cost-effective when compared to the concrete median barrier system and the system performed well, decreasing crossover accidents in the area. The cable median barrier system works well in medians with a minimum of 7 m width, where it is to be used to prevent the infrequent potentially catastrophic cross-median accidents. Conclusions: From December 1996 through March 1998, there were 53 barrier impacts, with 21 potential crossovers restrained from entering opposing traffic lanes. The fatality rate dropped from 0.6 per year for 1987 through 1996, to 0.0 per year for the study period. The injury accident rate increased from 0.7 per year for 1987 through 1996, to 3.8 per year for the study period. Cable system annual costs will always be less than concrete system annual costs for subject location, study period, and selected inflation rate.

Brett Sposito, Oregon DOT, 200 Hawthorne SE, Suite B-240, Salem, OR 97301-5192, Tel: (503) 986-2847, Fax: (503) 986-2844, Email: brett.l.sposito@odot.state.or.us; Samuel Johnston, Oregon DOT, Transportation Building, Fifth Floor, Salem, OR 97310, Tel: (503) 986-3572, Fax: (503) 986-4063, Email: samuel.a.johnston@odot.state.or.us.

990871 "W-Beam Guardrail"

Abstract: Several versions of the W-beam guardrail with differing details have been subjected to full-scale crash tests. Results of these tests have not presented a clearly defined relationship between details of the design and acceptability of performance. Results seem to indicate the capacity of W-beam guardrail is very close to demands of test level three and seemingly small variations in details make the difference between pass and fail. It also seems that blockouts that extend at least 200 mm in the transverse direction, remain in place, and hold their shape, result in better performance of the railing system. Conclusions: 1) The G4(1S) guardrail (W150×14 posts with W150×14 blockouts) does not meet test level 3 of NCHRP Report 350; 2) A W-beam guardrail with W150×14 steel posts and 150 mm × 200 mm routed wood blockouts does meet test level 3 of NCHRP Report 350; 3) A W-beam guardrail with W150×14 steel posts and 150 mm × 150 mm routed wood blockouts barely meets test level 3 of NCHRP Report 350; 4) A W-beam guardrail with W150×200 steel posts and 150 mm × 200 mm plastic blockouts (formed to same shape as routed wood blockouts) meets test level 3 of NCHRP Report 350; 5) A W-beam guardrail with 150 mm × 200 mm wood posts and 150 mm × 200 mm wood blockouts meets test level 3 of NCHRP Report 350; 6) A W-beam guardrail with W150×200 steel posts and W150×17.9 steel blockouts does not meet with test level 3 of NCHRP Report 350. One might be inclined to observe that W-beam guardrails with blockouts made of steel wide flange shapes do not meet test level 3 of NCHRP Report 350 and that those made of other materials (wood and plastic) do meet test level 3, and then conclude that there is a cause and effect relationship–steel wide flange blockouts cause failures. However, the details do not support that conclusion. It is observed that the W150×14 steel blockouts collapsed and seemed to allow significant interaction (snagging) of the vehicle on posts. The wood and plastic blockouts did not collapse. However, the W150×17.9 blockout did not collapse, yet that test failed. Observations are further complicated by the fact that the rail element was ruptured in the test with the W150×17.9 blockouts. Data presented in the report support the argument that test-to-test variation in Index Severity along with blockout distance could account for the otherwise unexplained pass/fail behavior of W-beam guardrails. Such a conclusion would be supported further if it is finally learned that test conditions 3-11 define the dividing line between acceptable and unacceptable performance of W-beam guardrails.

Eugene Buth, Senior Research Engineer, Texas Transportation Institute, College Station, Tx. 77843, Tel: 409 845 6159 Fax: 409 845 6107 Email: g-buth@tamu.edu; and Wanda L. Menges, Associate research Specialist, Texas Transportation Institute, College Station, Tx. 77843, Tel: 409 845 6157 Fax: 409 845 6107 Email: W-Menges@tamu.edu.

990956 "Videolog Assessment of the Vehicle Collision Frequency with Concrete Median Barriers on an Urban Highway in Connecticut"

Abstract: In-service performance evaluation is the process of assessing the performance of roadside safety hardware in real world service conditions. The purpose of in-service evaluation is to determine and document the manner in which a safety feature performs during a broad range of collision, environmental, operational, and maintenance situations for typical real world site and traffic conditions. An in-service performance evaluation of the concrete median barrier (CMB) in Connecticut was undertaken to determine (1) how often CMBs are struck and, (2) how often such collisions are reported to the police. This paper presents the method used to perform the in-service performance evaluation of the CMB as well as the results. Conclusions: This paper demonstrated several important things. First, videologging is an effective method for collecting in-service performance data on roadside safety hardware. In fact, for some types of systems, like the CMB, using videologging is the only safe feasible method for collecting data. Second, observed collision rates for this particular segment of high-volume high-speed urban highway indicated that the collision frequency on tangent and curved sections were approximately 0.0004 and 0.0012 collisions/km/vehicle/day, respectively. The collision rate on the curved segments was approximately three times greater than on the tangent sections. Third, neither the Roadside nor RSAP models of collision frequency provide a very realistic estimate of the number of collisions on this segment. This is probably due to the fact that the characteristics of this study segment were much different from the data sets used to develop the models of encroachment in RSAP and Roadside. The character and nature of vehicle encroachments and collision rates on high-volume high-speed highways in urban areas are still not well understood.

Michael S. Fitzpatrick Jr., University of Massachusetts, Department of Civil and Environmental Engineering, 214 Marston Hall, Amherst, MA 01003, Phone: (413) 256-3810, Email: mfitzpat@ecs.umass.edu; Kathleen L. Hancock, P.E., Ph.D., Assistant Professor, University of Massachusetts, Department of Civil and Environmental Engineering, 216 Marston Hall, Box 35205, Amherst, MA 01003-5205,Phone: (413) 545-0228, Fax: (413) 545-2840, Email: hancock@kirk.ecs.umass.edu; and Malcolm H. Ray, P.E., Ph.D., Associate Professor, Worcester Polytechnic Institute, Department of Civil and Environmental Engineering, 100 Institute Road, Worcester, MA 01609-2280, Phone: (508) 831-5340, Fax: (508) 831-5808, Email: mhray@wpi.edu.

991053 "Development of a Flared Energy Absorbing Terminal for W-beam Guardrails"

Abstract: A new flared W-beam guardrail terminal that incorporates energy absorbing technology has been developed and successfully crash tested to meet NCHRP Report 350 criteria. The terminal, designated the FLEAT-350, incorporates an impact head designed to dissipate impact energy by producing a series of plastic hinges in the W-beam as the impact head is pushed down the guardrail. The energy absorption mechanism allows the flared terminal to absorb large amounts of kinetic energy before the vehicle is allowed to gate through the system. Most components of the new terminal are similar to those incorporated in the SKT-350 terminal. The terminal system is 11.4 m (37.5 ft.) long and incorporates a straight flare with a final end offset of between 0.76 m (2.5 ft) and 1.2 m (4 ft). The terminal utilizes two breakaway posts in foundation tubes and fuve 150 mm x 200 mm (6 in. x 8 in.) rough cut CRT posts. The energy absorbing design minimizes the potential problem associated with vehicles penetrating the terminal and impacting slopes, ditches, or other hazards behind the guardrail while still traveling at a high rate of speed. Further, the new design has fewer components and is less sensitive to post location and installation details than some other flared systems. Conclusions: The FLEAT-350 has been designed to provide energy absorbing performance in a flared configuration. The new terminal should be able to safely decelerate most impacting vehicles and minimize high-speed penetrations of the system. The variable offset of the new terminal allows it to be placed at many sites where there is insufficient space for a conventional flared system and reduce the need for costly "berms" when other flared terminals are placed near roadside slopes. The straight flare should be easy to construct and insensitive to post locations. Laying out the post locations is as simple as using a string line between the start of the flare and the end post. Further, because the terminal does not rely on global buckling of a W-beam rail element as its primary method for controlling impact forces, it does not require a parabolic flare. As a result, the new design is much less sensitive to precise post locations. The limited number of components used in this design also simplifies installation.

Dean L. Sicking, Midwest Roadside Safety Facility, University of Nebraska-Lincoln, W348 Nebraska Hall (0531), Lincoln, NE 68588, Phone: (402) 472-9332, Fax: (402) 472-2022; John R. Rohde, Midwest Roadside Safety Facility, University of Nebraska-Lincoln, W348 Nebraska Hall (0531), Lincoln, NE 68588, Phone: (402) 472-8807, Fax: (402) 472-2022; and John D. Reid, Mechanical Engineering, University of Nebraska-Lincoln, 255 Walter Scott (0656), Lincoln, NE 68588, Phone: (402) 472-3084, Fax: (402) 472-2022, jreid@unl.edu.

991112 "Development of a Flared End Treatment to NCHRP Report 350; REGENT System"

Abstract: A project to develop a flared guardrail end treatment system that would meet NCHRP 350 Test Level 3 (100Km/hr) requirements was initiated at the request of certain D.O.T. officials and a group of guardrail manufacturers that did not have access to such a system. This was a major concern to this guardrail group that needed to have access to such a system prior to the October 1998 implementation date for NCHRP Report 350 roadside hardware. A set of design, performance, and cost objectives were established and a decision was made to qualify the system for both weak and strong soils. The development project resulted in a new type of design and specifications for the wood posts used in the terminal section. The redirective, gating end treatment (REGENT( System) was designed, tested to NCHRP Report 350 (Test Level 3) conditions and was approved for use on the National Highway System by the Federal Highway Administration. The REGENT system was tested when attached to both wood and steel downstream guardrail posts. Conclusion: The REGENT( System has been designed, tested and evaluated in accordance with the guidelines in NCHRP 350 Report (1) for redirective, gating guardrail end treatments, at Test Level 3 (100Km/hr). The system was tested in a weak soil condition and demonstrated performance that indicates that acceptable performance would also be expected in strong soils. The REGENT( System was tested when attached to downstream guardrail systems that utilized steel or wood posts and demonstrated acceptable performance under both conditions. The REGENT( System has been accepted by FHWA to NCHRP Report 350 (1), Test Level 3, and is cost competitive with other flared end treatments that have been approved. Its installation characteristics (level of complexity and costs to install) are similar to the other flared terminals, and it is the only end treatment accepted for use in weak as well as strong soil conditions. Thus, the REGENT( System has met the initial design objectives of the research project. The research project uncovered a potential problem area for other guardrail end treatments and longitudinal guardrail systems utilizing wood posts in soil. The issues involving post/soil interaction have also been raised by Rhode, et al from research done at the University of Nebraska – Lincoln and by Ray et al from research done at Iowa State University. Based on the findings in the REGENT( project and reports from the universities, it is recommended that further research be carried out to determine if the design of wood posts used in end treatments or the way these end treatments are specified without concern for soil conditions should be modified.

Owen S. Denman, P.E., E-Tech Testing Services, Inc., 3617-B Cincinnati Avenue, Rocklin, California 95765; and James B. Welch, Energy Absorption Systems, Inc., 3617 Cincinnati Avenue, Rocklin, CA. 95765, Phone: (916) 645-8181, Fax: (916) 645-3495.

X. SOILS, GEOLOGY, AND FOUNDATIONS

990284 "NCDOT’s Experience With Predesign Load Testing"

Abstract: Load test programs performed in the predesign stage provide the greatest potential for savings in more economical foundation designs. The NCDOT’s first experience with predesign load testing was on the Neuse River Bridge project in 1994. Subsequently, the practice was utilized on all major bridges thereafter. This paper presents a case history of those projects detailing the load testing, outcome, and estimated cost savings. Through the case history, the paper discusses both the successful application of load test programs and the results that were achieved. A description of the NCDOT’s experience and practice of predesign load testing of deep foundations is presented. The philosophy and considerations used by the NCDOT to evaluate and develop load test programs are discussed. The impact on design and construction practices that have occurred as a result of load testing and experiences in mitigating constructability problems and construction claims through the use of load test programs are described. The progression of the NCDOT’s load test experiences and integration of new load test technologies are also presented. Conclusions: The experience of the NCDOT has been that predesign load test programs save money in better foundation designs, mitigate constructability problems and reduce exposure to construction claims. Savings from the use of predesign load test programs is a function of project size, subsurface and site conditions, test program comprehensiveness, project schedule and the expertise of the design team. The predesign load test programs employed by the NCDOT resulted in estimated savings of between 1% to 11% of project costs. Innovation has come mainly in the form of state-of-the-art geotechnical testing equipment such as the Pile Driving Analyzer (PDA), Osterberg Load Cell, Statnamic, Pile Integrity Test (PIT), Crosshole Sonic Logger (CSL), and EL Vertical In-Place Inclinometer. Recommendations: The Statnamic technology could be an essential tool in advancing the state-of-practice of dynamic soil response for designing foundations to withstand vessel impacts. Other state DOT’s should consider implementing predesign load test programs for applicable projects. Careful planning and the use of the best technology is crucial for cost effectiveness. A standard practice for evaluating feasibility and designing predesign load test programs needs to be developed. There is a definite need for a standard to ease implementation and optimize savings. A database of load test results in a standardized format needs to be developed. Currently, data sharing between state DOT’s is difficult and inadequate.

John Fargher, P.E., Email: jfargher@dot.state.nc.us, Nariman Abar, P.E., Email: nabar@dot.state.nc.us, Jamey Batts, P.E., Email: jbatts@dot.state.nc.us, Brian Keaney, P.E., Email: bkeaney@dot.state.nc.us, and Sean Byrne, E.I.T., Email: sbyrne@dot.state.nc.us, North Carolina Department of Transportation (NCDOT), Design Services Unit, Soils and Foundations Design Section, 1020 Birch Ridge Road, Building B, P.O. Box 25201, Raleigh, North Carolina 27611, Phone: (919) 250-4128, Fax: (919) 250-4119.

990410 "Development of Cement Treated Open Graded Drainage Layer Placement Techniques in Ontario"

Abstract: The effectiveness of the subsurface drainage system is a primary factor influencing long-term pavement performance. Pavement research indicates that pavement drainage systems increase pavement life, lower maintenance costs by minimizing the risk of subgrade softening and differential frost action. For rigid pavements, optimum transverse joint performance is achieved when the concrete pavement overlies a highly permeable base layer promoting subsurface drainage, as well as a layer that is structurally stable providing uniform support to the slab. This type of slab support eliminates the potential for loss of slab support from fine migration from pumping action over time. The Ministry of Transportation, Ontario (MTO) recognizes the benefits of high performance pavement drainage systems and several years ago adopted open graded drainage layers (OGDL’s) for design of freeways. This paper outlines the material development, and subsequent construction and quality control activities completed during construction of test sections on a major freeway in Southern Ontario in 1996 and 1997. The work conducted along with the trials, established that Portland cement treated OGDL placed with conventional asphalt paving equipment, is, a viable alternative to asphalt treated OGDL based on costs and drainage properties. Conclusions: On the basis of the results of monitoring the 1997 trials, and 1992 test sections, it is concluded that comparable CTOGDL mix properties and compacted layer conditions can be achieved using both slipform concrete pavers and properly equipped asphalt spreaders. Satisfactory pavement structure performance has been recorded to date on the 1992 trial, and similar pavement performance is anticipated on the 1997 trial sections. The use of CTOGDL is considered to be an acceptable alternative to asphalt treated OGDL.

Tom Kazmierowski, P.Eng., Manager, Pavements and Foundations Section, Ministry of Transportation, Ontario, Room 232, Central Building, 1201 Wilson Avenue, Downsview, ON M3M 1J8, Phone: (416) 235-3512, Fax: (416) 235-3919, Email: kazmiero@mto.gov.on.ca.

990421 "Soil Reinforcements in MSE Structures: A Rationale for the Determination of Long-term Admissible Tensile Loads"

Abstract: The paper presents a single, logical and consistent approach to the concept of safety for the basic types of earth reinforcing materials and their long-term admissible tensile loads. It exposes the principles of the method elaborated by Groupe TAI after decades of practice in the soil reinforcement industry and participation in the drafting of the relevant codes and standards. A number of innovative, though rational, features are presented, specifically: three categories of reinforcements are defined, and the partial factor of safety related to the long-term strength of the reinforcement: depends on the classification, is a function of service life and product experience, is applied to the loss of strength (not the remaining strength) The approach applies to polymeric as well as metallic soil reinforcements. An example is presented at the end of the paper for the particular case of steel strips and grids. It is hoped that this contribution to a sound and common approach of the long term safety in the design of MSE structures will help to progressively make the various existing (or future LRFD) codes more compatible between them and more equitable for the diverse types of reinforcements which they deal with.

Pierre Segrestin, Malcolm S. Boyd, and Jean-Marc Jailloux, Groupe TAI, Tel: 33

(0)1 34 80 49 04, Fax: 33 (0)1 34 80 49 62, Email: psegrestin@compuserve.com.

990612 "Field Demonstration of Highway Embankment Construction Using Waste Foundry Sand"

Abstract: Considerable savings are available to the metal casting industry through the development of reuse applications for their waste foundry sand (WFS). Furthermore, generators frequently are willing to provide WFS to reusers at no cost. Laboratory investigations have indicated that WFS from ferrous foundries can provide the necessary engineering properties for a highway embankment and that the Microtox_ bioassay test can be used to screen the 'toxicity' of WFS to prevent a negative environmental impact. In 1996, the Indiana Department of Transportation (INDOT) and Purdue University constructed a demonstration embankment using WFS, followed by extensive monitoring to evaluate geotechnical and environmental performance. Stockpile and job site 'grab' WFS samples were also tested. Conclusions: Geotechnical results indicated that WFS can perform well as a structural fill with strength and deformation characteristics comparable to natural sand, but cannot be considered as freely draining. Environmental testing consisted of Microtox_ and Nitrotox bioassays, ion chromatography, and inductively coupled plasma spectrophotometer testing for metals. Bioassay results indicate the WFS have not resulted in inhibitions (toxicity) higher than those expected from natural sands. Ion migration from the WFS into the foundry sand lysimeter was found, supporting bioassay data, but at concentrations below reuse regulatory criteria. Metal concentrations were generally below Indiana regulatory reuse Type III criteria and typically below Drinking Water Standards. Overall, the WFS did not result in a negative environmental impact on the site. State environmental regulatory agencies were the most frequently identified source of barriers to the beneficial reuse of WFS and reuse is further compounded by the lack of decision-based scientific tools such as life-cycle or risk-based analysis methods. The resultant liability exposure from state and federal regulations was the prevailing concern expressed by Departments of Transportation (DOTs) when considering using a regulated waste such as WFS. Furthermore, foundries often lack an organizational commitment to the reuse of its WFS as evidenced by the lack of both product quality control and a marketing strategy.

Barry K. Partridge, Ph.D., Chief, Division of Research, Indiana Department of Transportation, Tel: 765-463-1521, Fax: 765-497-1665, part_envir@hotmail.com; Patrick J. Fox, Associate Professor of Geotechnical Engineering, Purdue University, Tel: 765-494-0697, Fax: 765-496-1107, pfox@ecn.purdue.edu; and James E. Alleman, Professor of Environmental Engineering, Purdue University, Tel: 765-494-7705, Fax: 765-496-1107, alleman@ecn.purdue.edu.

990721 "Durability Effects On Resilient Moduli Of Stabilized Aggregate Base"

Abstract: A laboratory study was conducted to examine the durability of CKD-stabilized aggregate base, as measured by resilient modulus, unconfined compressive strength and layer coefficient. Specifically, the effect of freezing/thawing and wetting/drying was evaluated. The Meridian limestone aggregate, which is considered to be of substandard quality and therefore unsuitable for highway base courses, was used as the raw material and also stabilized with cement-kiln-dust. A testing protocol is proposed to quantify the effect of freezing/thawing and wetting/drying. Conclusions: The RM values of the raw Meridian aggregate were in the range 49.42 MPa to 306.59 MPa, within the tested stress level. These values are low and may be inadequate for most applications. The data demonstrated that cement-kiln-dust is an effective stabilizing agent for strengthening the Meridian aggregate intended for base/subbase construction. With the addition of 15% CKD, the RM values increased manifold up to 499.51 MPa. Freezing/thawing and wetting/drying cycles have considerable adverse effect on the durability as measured by the resilient modulus of CKD-stabilized aggregate. Within a range of 8 cycles, the RM values decreased substantially with increasing number of freezing/thawing and wetting/drying cycles. The highest reduction in RM value due to freezing/thawing was 54.21%, 67.51% and 65.11% for 4, 8, and 12 cycles, respectively. For wetting/drying actions, the highest reduction in RM value was 34.27%, 53.58% and 61.88% for 4, 8, and 12 cycles, respectively. The layer coefficients of the stabilized aggregates are significantly higher than those of the raw aggregates. However, the layer coefficient of the stabilized aggregate base dropped significantly when the aggregate experienced freezing/thawing and wetting/drying cycles. When subjected to about eight cycles of freezing/thawing and wetting/drying, the layer coefficients of CKD-stabilized aggregate base assumed values close to or lower than those of the raw aggregate base. This investigation points to the need to explore more in depth the durability studies and recommend a protocol of freeze/thaw, wet/dry testing methodology.

Musharraf M. Zaman, Jianhua Zhu, and Joakim G. Laguros, School of Civil Engineering and Environmental Science, The University of Oklahoma, 202 West Boyd Street, Room 334, Norman, OK 73019-1024, Tel: (405) 325-5911, Fax: (405) 325-4217, Email: zaman@ou.edu.

990723 "Finite Element-Based Seepage Design Charts for Sheet Piles Penetrating Heterogeneous Media"

Abstract: Seepage and exit gradient quantities due to flow around sheet piles embedded in geological strata are of great significance to geotechnical/bridge foundation engineers since these quantities play essential part in producing an overall economical and efficient design. In this research study an effective and accurate method for obtaining seepage and exit gradient estimates under similar hydraulic structures was developed. To achieve this objective, the finite element method was successfully implemented for providing seepage and exit gradient estimates under single sheet piles penetrating heterogeneous media. The data obtained form the numerical model was compiled and plotted to form different sets of design charts. These charts could be used efficiently for obtaining seepage and exit gradient estimates under the aforementioned hydraulic structure. The results obtained from the finite element model were compared and verified against existing relevant mathematical approximation and other techniques. Designers and practitioners in the geotechnical/bridge engineering fields would greatly benefit from these charts because of their simple yet accurate estimates. Moreover, the applicability of the developed design charts was demonstrated through solution of various design problems. Conclusions: The finite element analysis of the two-dimensional seepage problem under consideration was successful in furnishing substantial amount of data that was summarized to produce different sets of efficient and simple to use design charts. The accuracy and validity of the seepage and exit gradient estimates obtained from the finite element-based design charts were comparable to those of relevant mathematical approximation, accurately drawn flownets, and other numerical models. Designers and practitioners in the geotechnical/bridge engineering fields would greatly benefit from the developed charts in their analysis and/or design tasks of transportation engineering applications involving similar hydraulic structures.

Yacoub M. Najjar, Associate Professor, Dept. of Civil Engineering, Kansas State University, Manhattan, KS 66506.

990725 "Experimental Study Of Micro-Mechanisms Governing The Behavior Of Weakly Cemented Rocks"

Abstract: Some weakly cemented, high porosity rocks exhibit a high degree of compaction and do not undergo the traditional shear failure under triaxial and uniaxial loading. An experimental study was undertaken in which a weakly cemented, high porosity rock was subjected to truly triaxial stress conditions. Petrographic thin sections were prepared from both undeformed and deformed specimens and were carefully examined under an optical microscope. Long and short axes of the calcite and fossil grains as well as their orientations were measured along selected traverses. The micro-mechanisms established in this study could be used to develop constitutive models in the future and to analyze and interpret field data pertaining to many transportation-related problems. Conclusions: An attempt was made in this study to delineate the micro-mechanisms responsible for pore collapse. Crystal plasticity (twinning of calcite grains), and cataclastic flow (grain crushing) are prominent mechanisms that have been documented as being operative during pore collapse. Grain boundary slip and rigid body rotation of grains probably occur but cannot be positively identified. Probably all three mechanisms are operative throughout pore collapse, but certain mechanisms tend to be dominant at different stages. At an early stage of pore collapse, cataclastic flow by grain crushing and grain boundary slip are the dominant mechanisms of pore collapse. During this stage, most pore volumetric reduction seemingly is due solely to these two mechanisms. At this stage, there is no obvious microfracturing and/or twinning in the samples. During the middle of pore collapse (up to 6 ksi or 41.4 MPa), crystal plasticity along with cataclastic flow tend to dominate. At the middle of the second stage, calcite grains are more twinned than in the previous stage. By the end of the third stage (i.e., at 25 ksi (172.5 MPa) stress level), almost all the calcite grains are heavily twinned. Crystal plasticity becomes increasingly dominant as pore collapse process progresses.

Musharraf M. Zaman, Thurman E. Scott, Jr., Santanu Mowar, and Jean-Claude Roegiers, School of Civil Engineering and Environmental Science, The University of Oklahoma, 202 West Boyd Street, Room 334, Norman, OK 73019-1024, Tel: (405) 325-5911, Fax: (405) 325-4217, Email: zaman@ou.edu.

991050 "Non-Invasive Measurement of Permanent Strain Field Resulting from Rutting in Asphalt Concrete"

Abstract: Asphalt concrete is a bonded granular material composed of aggregates and asphalt binder. The chemical, physical and mechanical properties of the constituents are different. Under typical repeated tire loads, the aggregates do not deform but instead rigidly translate and rotate within the binder. Rutting is the surface manifestation of the internal structure evolution in asphalt concrete under repeated wheel loading. In this paper, a procedure which was developed to quantify the permanent strain field of asphalt concrete underlying the rutted zone produced by an accelerated wheel testing device is described. The new procedure, which is non-invasive, has been automatically implemented in a computer program named MATCH that was developed to compare the locations of particles before and after testing and therefore permit the displacement of individual particles to be tracked. Pattern recognition based on each particle?s cross sectional area, perimeter and aspect ratio was used to match the particles. Application of the new procedure to measure the permanent strain field of an asphalt concrete specimen in a Georgia Loaded Wheel Tester is described. The reliability of the procedure for automatically matching the particles in successive images was confirmed by manual procedures. Conclusions: It was found that the permanent strain and the mastic/solid area ratio evolution measured in this application demonstrated strong localism. The evolution of the mastic/solid area ratio indicated the zone under the wheel dilated whereas the zone away from the wheel contracted. Dilatancy and contraction were quite significant locally but insignificant globally. The direct strains, shear strains and volumetric strains all demonstrated particle configuration dependency. The strains in the mastic were much larger than the global or macro-strain. The proposed procedure has significance in the future study of micro-macro properties of bonded granular materials and how factors such as aggregate size, shape and distribution affect the global response.

Lin-Bing Wang, J. David Frost (contact author) and James S. Lai. Georgia Institute of Technology, Tel: (404) 894-2280, Fax: (404) 894-2281, Email: dfrost@ce.gatech.edu

991140 "Measured Pile Setup During Load Testing and Production Piling I-15 Corridor Reconstruction Project, Salt Lake City, Utah"

Abstract: As part of the I-15 Corridor Reconstruction Project through downtown Salt Lake City, 9 sets of full scale load tests were performed at locations selected as representative of the subsurface conditions along the Corridor alignment. The test program included dynamic monitoring of pile installation and restrike events using high strain testing and analysis methods. Subsurface conditions along the alignment range from deep clays, often interspersed at depth with dense sand lenses, to locations where dense alluvial sands provide foundation support above the groundwater table. The piles derive their support from shaft friction or a combination of shaft friction and endbearing, depending on the strata present. The test and production piles consistently indicate setup occurs regardless of the subsurface conditions. The setup in the soft to stiff lakebed clays is attributed to remolding of the clays during pile driving and subsequent reconsolidation. The magnitudes of setup and the trend of capacity gain with time are similar to those found elsewhere in submerged cohesive deposits having a broad range of insitu strengths. The setup in the dense sands is comparable to setup previously described by others in dense marine sands. Based on strong correlations between static and dynamic test estimates of pile capacities, relationships have been developed to predict long-term pile capacity using dynamic test results from end of installation (EOI) and restrike events for representative subsurface conditions along the alignment. A setup unit friction of 57.5 kPa (1.2 ksf) when added to the EOI dynamic capacity predicted the measured load test capacity within 20 percent for all piles tested, and within 10 percent for the friction/endbearing piles that are the most common production piles. These relationships are being used to assist in the estimation of long-term pile capacity based on installation and/or short-term restrike testing of selected piles. This approach serves as an important component of QC/QA piling acceptance procedures.

Attwooll, William J., Terracon, 301 N. Howes, Fort Collins, CO 80521, Tel: (970) 484-0359, fax: (970) 484-0454, Email: wjattwooll@terracon.com; Holloway, D. Michael, InSituTech, 5 del Valle, Orinda, CA 94563, Tel: (925) 254-0460, fax: (925) 254-0461, Email: dmh@insitutech.com; Rollins, Kyle M., Department of Civil and Environmental Engineering, Brigham Young University, 368 Clyde Building, Provo, UT 84602, Tel: (801) 378-2811, fax: (801) 378-4449, Email: rollinsk@et.byu.edu; Esrig, Melvin I., URS-Woodward Clyde, 201 Willowbrook Boulevard, Wayne, NJ 07470, Tel: (973) 785-0700, fax: (973) 785-0023, Email: esrigs@aol.com; Sakhai, Si, Utah Department of Transportation, 4501 S. 2700 W., West Valley City, UT 84119, Tel: (801) 965-4196, fax (801) 965-4796; Hemenway, Dan, Wasatch Constructors, 480 N. 2200 W., Bldg. B, 2nd Floor, Salt Lake City, Utah 84116, Tel: (801) 594-6300, fax: (801) 594-6332.

991152 "Prediction Of Pile Set-Up In Clay"

Abstract: Reliable calculations of pile set-up times represent a critical parameter in the design of large diameter pipe piles that are used to anchor offshore tension leg platforms. The underlying mechanism of set-up for driven piles in soft clays can be related to the changes in radial effective stress that occur during installation and subsequent radial dissipation of excess pore pressures. These processes have been analyzed using the strain path method in combination with the MIT-E3 effective stress soil model and non-linear finite element methods. The predictions show that the radial effective stress at full set-up (Kc = s’rc/s’v0, where s’v0 is the in situ vertical effective stress) depends primarily on the OCR, pile geometry (open vs closed-ended) and strength properties at large shear strains. The predicted range of Kc values are in good agreement with the current database of high quality field measurements on instrumented piles in both low plasticity and high plasticity clays. The paper demonstrates the normalization of pore pressure dissipation and effective stress responses (Du/Dui and K/Kc) using a dimensionless time factor, T = (s’pkt)/(gwReq2), where t is the time after pile installation, gw the unit weight of water, and Req the equivalent radius of a closed-ended circular pile. Reliable predictions of set-up depend on accurate estimation of the OCR (= s’p/s’v0) and hydraulic conductivity, k. The paper presents two examples which show that good predictions of set-up can be achieved using measurements of k from laboratory tests. However, even at well documented test sites it is difficult to refine estimates of k within a factor of 2-3. Further research is needed to achieve similar levels of predictive capability for piles in more highly overconsolidated clays.

Andrew J. Whittle, and Twarath Sutabutr, Massachusetts Institute of Technology, Tel: (617)-253-7122 Fax: (617)-253-6044, Email: ajwhittl@mit.edu.

991362 "Resilient Modulus of Soft Soil Beneath High Speed Rail Lines"

Abstract: Modern high-speed rail lines are increasingly being built on marginal land so as to reach city centres whilst avoiding housing areas. Often this land is composed of soft alluvial soils, which exhibit a low resilient modulus. This paper discusses the measurement, prediction, modelling and implications of resilient modulus values for such subgrades. Measurement; considers the use of repeated load triaxial testing, resonant column and in-situ methods, illustrating these with sample data. Prediction draws on both analytical and finite element techniques to illustrate the critical speed (the ‘bow-wave’ effect) and how it is influenced by resilient modulus. Modelling discusses the available relationships for deriving subgrade stiffness for this dynamic situation and their limitations. Implication then uses these to define the relevant effects of resilient modulus values on design problems and outlines possible geotechnical solutions. Conclusions: The phenomenon of dynamic magnification of vertical displacements of a railway line crossing soft soil has been identified and analyzed. The model used can be defined using two non-dimensional parameters. The first relates to the relative speed of the train compared to the stiffness of the track foundation. The second non-dimensional parameter relates to the damping of the overall system. The foundation model used is a Winkler model and, therefore, a coefficient of subgrade reaction is required. It is possible to relate the resilient soil modulus to the coefficient of subgrade reaction and to provide design criteria for trains crossing soils with a low resilient modulus.

Michael E. Heelis, Andrew R. Dawson, Andy C. Collop and David N. Chapman, University of Nottingham; Victor V. Krylov Nottingham Trent University Tel (44) 115 9513902 Fax (44) 115 9513898.

991442 "A Regression Model for Resilient Modulus of Subgrade Soils"

Abstract: Subgrade soil is an important part in both flexible and rigid pavement structures. AASHTO recommends the use of bulk stress and deviatoric stress models to characterize granular and cohesive soils respectively. However, these models oversimplify the fundamental behavior of subgrade soils. This paper proposes the use of an octahedral stress state model to characterize the resilient modulus of different soils. Eight different soils representing major soil types in Louisiana have been selected to validate the model and to calibrate the model parameters. Additional analysis is then performed to develop correlations between the model parameters and other soil properties. Three types of correlation have been produced: 1) model parameter—soil properties correlation, 2) model parameter—CBR correlation and, 3) model parameter—UCS correlation. Statistical analysis indicates that the correlation between model parameter and soil properties yields the best results. Conclusions: This study verifies a non-linear resilient modulus model uses normalized octahedral normal and shear stresses interprets soil test result better than simple bulk stress and deviatoric stress models. Three relations for the octahedral resilient modulus model have been developed through regressions. The relation between basic soil properties and resilient modulus model parameters gives the best prediction among the three regression models.

Louay N. Mohammad, Baoshan Huang, Anand Puppala, and Aaron Allen. Louisiana Transportation Research Center, Tel: 225-767-9126, Fax 225-767-9108, Email: louaym@ltrc.lsu.edu.

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