980039 “Effect of Rubber Tire Grinding Method on
Asphalt-Rubber Binder Characteristics”
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980213 “Aggregate Toughness/Abrasion Resistance and
Durability/Soundness Tests Related to Asphalt Concrete Performance in
Pavements”
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980224 “Characterization Tests for Mineral Fillers Related to
Performance of Asphalt Paving Mixtures”
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980296 “Effect of Mineral Filler Type and Amount on the Design
and Performance of Asphalt Concrete Mixtures”
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980573 “The Engineering Properties of Polymer Modified Asphalt
Binders”
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981526 “Georgia’s Experience with Recycled Roofing Shingles in
Asphaltic Concrete”
Abstract: This paper presents the results of a study carried out to
evaluate the effect of the rubber grinding processes on the properties and
characteristics of the resulting asphalt-rubber binder. Several ambient and
cryogenic ground tire rubber (GTR) materials were evaluated using measurements
of surface areas and bulk densities. The rubber materials were then,
respectively, mixed with an AC-30 asphalt, and the resulting blends were tested
to determine the corresponding viscosity, settlement during storage, and the
potential for binder draindown. Conclusions: The findings indicate that
the asphalt-rubber binders produced with rubber from the different grinding
processes have measurable differences in properties and storage characteristics
which are critical to the performance of the binder in open- graded mixtures.
The wet-ground rubber material had substantially lower bulk densities and larger
surface areas than rubber resulting from other grinding methods. GTR materials
with greater specific surface areas, and more irregular shaped particles
produced asphalt-rubber binders having higher viscosities. Binders with the
cryogenic ground rubber had the greatest amount of settlement and the least
resistance to draindown.
Randy C. West, APAC, Inc., 3013 Fort Cobb Drive,
Smyrna, GA 30080. Tel: (404) 392-5300 Fax: (404) 392-5350. Gale C. Page, John
Veilleux, Bouzid Choubane, Florida Dept. of Transportation, State Materials
Office, 2006 N.E. Waldo Road, Gainesville, FL 32609. Tel: (352) 337-3100 Fax:
(352) 334-1649
Abstract: Numerous tests have been developed to empirically characterize
aggregate without, necessarily, a strong relationship with the performance of
the final products incorporating these aggregates. This seems to be particularly
true for aggregate "toughness and abrasion resistance" and "durability and
soundness". The purpose of this research was to identify and evaluate
toughness/abrasion resistance and durability/soundness tests for characterizing
aggregate used in asphalt concrete and to determine those test methods that best
correlate with field performance. Based on a review of literature and
specifications, laboratory tests for characterizing aggregate toughness/abrasion
resistance and durability/soundness were selected. Sixteen aggregate sources
with poor to good performance histories were identified for evaluation with the
selected suite of tests. Performance histories of pavements containing these
aggregates in asphalt concrete layers were established through personal contacts
with state transportation agencies and performance evaluation questionnaires.
Aggregate properties from laboratory tests were correlated with field
performance. Conclusions: The qualitative visual examinations of plots of
aggregate properties and pavement performance ratings, based on
toughness/abrasion resistance and durability/soundness, suggest Micro-Deval and
magnesium sulfate loss are the two best indicators of potential pavement
performance. Losses of 18% for both tests appear to separate good and fair from
poor performers. It is recommended that state transportation agencies begin to
run the Micro-Deval and magnesium sulfate soundness tests on available aggregate
sources.
Yiping Wu, Office of Materials and Research, Georgia Department of
Transportation, 15 Kennedy Dr., Forest Park, GA 30050. Tel: (404) 363-7537 Fax:
(404) 363-7684. e-mail: yipingwu@ix.netcom.com Frazier Parker,
Highway Research Center, 238 Harbert Engineering Center, Auburn University, AL
36849-5337, Tel: (334) 844-6284 Fax: (334) 844-6290. e-mail: fparker@eng.auburn.edu Prithvi Kandhal,
National Center for Asphalt Technology, 211 Ramsay Hall, Auburn University, AL
36849. Tel: (334) 844-6242 Fax: (334) 844-4485. e-mail: pkandhal@mail.auburn.edu
Abstract: Various studies have shown that the properties of mineral
filler, especially the material passing 0.075 mm (No. 200) sieve (generally
called P200 material), have a significant effect on the performance of asphalt
paving mixtures in terms of permanent deformation, fatigue cracking, and
moisture susceptibility. However, researchers have employed different
characterization tests for evaluating the P200 materials. This study was
undertaken to determine which P200 characterization tests are most related to
the performance of asphalt paving mixtures. Six P200 materials representing a
wide range of mineralogical composition and particle sizes were used. These P200
materials were characterized by six tests including Rigden voids, particle size
analysis, and methylene blue test. Mixes were prepared with two fines/asphalt
ratios (0.8 and 1.5) by weight. Conclusions: The following P200 tests
that are related to HMA performance based on the statistical analysis are
recommended for evaluating aggregates for hot mix asphalt mixtures: 1- for
permanent deformation, the D60 and Methylene Blue tests, 2- for fatigue
cracking, no test is recommended, and 3- for stripping, the D10 and Methylene
Blue tests.
Prithvi S. Kandhal, Cynthia Y. Lynn, National Center for Asphalt
Technology, 211 Ramsay Hall, Auburn University, AL 36849-5354. Tel: (334)
844-6242 Fax: (334) 844-4485. e-mail: pkandhal@eng.auburn.edu. Frazier
Parker, Highway Research Center, 238 Harbert Engineering Center, Auburn
University, AL 36849-5337
Abstract: Three methods for classifying aggregate particle shape and
texture -- AASHTO TP33, ASTM D3389 and the flow rate method were evaluated in
this study. These methods were used to rank four natural river sands and a
crushed granite from good to poor performance based on the criteria established
in each method. Test results indicate that all methods easily distinguished the
crushed aggregate from the natural river sands. All the test methods were found
to be repeatable, each having low coefficients of variation for all the
aggregates tested. In order to evaluate the effect of particle shape and
texture, and mineral filler content on mix performance, one natural sand which
was ranked as "average performing" was selected and blended with the crushed
granite in the proportion of 20 percent natural sand and 80 percent crushed
granite. Asphalt-aggregate mixtures containing 4, 6, 8, and 12 percent mineral
were designed using the Marshall procedure, with the optimum asphalt contents
selected to yield mixtures with 5.0% air voids. Conclusions: Contrary to
priori expectations, increase in the amount of mineral filler was found to
decrease the optimum asphalt content if 5.0% air voids is used as the optimum
selection criteria. Marshall stability and unit weight also increased with
increase in mineral filler content. The addition of 20% natural fines was found
to decrease the asphalt content and increase the Marshall stability. To evaluate
the permanent deformation performance, mixtures containing 4, 8, and 12 percent
mineral filler were tested in repeated shear test at constant height (RSCH).
Within the range of mineral filler type and contents used in this study, results
indicate that mixtures containing 100 percent crushed granite show lower
accumulation of permanent strain as compared to an 80/20 blend of crushed
granite and natural sand; and an increase in mineral filler content of a mixture
was found to decrease its accumulated permanent strain while increasing the
mixture shear resilient modulus.
Akhtarhusein A. Tayebali, Glen A. Malpass,
N. Paul Khosla, North Carolina State University. Tel: (919) 515-7611 Fax: (919)
515-7908. e-mail: mailto:tayebali@%20eos.ncsu.edu.
Abstract: A large research program sponsored by the Michigan Department
of Transportation was designed and completed to evaluate the effect of polymer
modification on the various properties of asphalt mixtures. These include: the
micro and macro-structural, morphological, chemical, and engineering properties.
This paper presents and discusses some of the engineering properties of the SBS
and SEBS polymer modified asphalt mixtures. The elastic, fatigue, tensile, and
permanent deformation properties were investigated at 60, 25, and -5 o C and are
presented in this paper. Conclusions: 1. The SBS and SEBS polymer systems
considerably increase the indirect tensile strength and fracture toughness of
asphalt mixtures at 25 and 60 o C. This implies increased resistance to fatigue
cracking and rutting. 2. The higher number of load cycles to develop the same
plastic deformations (horizontal and vertical) and the almost constant resilient
modulus indicate that the SBS and SEBS polymer systems cause a decrease in the
energy stored in the sample due to plastic deformation. Since the applied cyclic
load was the same for all mixtures, it implies that the plastic properties of
PMA mixtures improve at 25 o C. 3. Fatigue life of PMA mixtures is considerably
higher than the straight and processed asphalt mixtures. The increase in fatigue
life is due to increases in the tensile strength and in the plastic properties
of the mixes. 4. The SEBS polymer system appears to have no impact on the low
temperature.
Dr. G. Y. Baladi, M. J. Khattak. Pavement Research Center of
Excellence, Dept. of Civil and Enviromental Engineering, 3546 Engineering
Building, Michigan State University, East Lansing, MI 48824. Tel: (517)-355-5147
Fax: (517)-432-1827.
Abstract: Reuse of roofing shingle waste not only minimizes the
environmental problems related to the disposal of waste in landfills, but it
also reduces the amount of virgin asphalt cement and fine aggregate required in
Hot Mix Asphaltic Concrete (HMAC), thus creating the potential for cost savings.
The Georgia Department of Transportation (GDOT) has experimented with the
recycling of roofing shingles in HMAC by constructing two test sections during
1994 and 1995. The source of the waste roofing shingles used in both test
sections was waste generated by a roofing manufacturer and generally consisted
of discolored or damaged shingles. One test section was constructed on Chatham
Parkway in Chatham County and one on State Route 21 in Effingham County. GAF
Building Materials, Inc. located in Savannah provided the waste shingle
material, and APAC Georgia, Inc. located in Savannah produced and placed these
experimental mixtures. To date, both test sections are performing well compared
with the unmodified control sections. Conclusions: Based on the
performance of these test sections, shingle manufacturing waste is allowed as a
recycling material in HMAC, just as reclaimed asphalt pavement (RAP), for GDOT
projects. A specification allowing post-consumer roofing shingle waste to be
used is also being proposed. Standard GDOT quality control procedures appear
satisfactory for evaluating mixtures containing roofing shingles.Although states
have experimented with higher percentages, Georgia has no plans at this time to
use greater than 5% of waste shingles by total mix weight.
Donald E. Watson,
Andrew Johnson, Hem R. Sharma, Georgia Department of Transportation, Office of
Materials and Research, 15 Kennedy Drive, Forest Park, Georgia 30297. Tel :(404)
363-7521 Fax :(404) 363-7684. e-mail: watson_d@dot.state.ga.us
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