980128 “Permeability Specification for High Performance Concrete Decks”
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980139 “Shrinkage of High Performance Concrete Overlays on
Route 60 in Virginia”
Abstract: Chlorides from deicing salts and a marine environment
infiltrate concrete and initiate corrosion of the steel reinforcement. Rust
formation results in expansion that may cause cracking and delaminations. Other
harmful solutions may also cause distress because of alkali-silica reactivity,
sulfate attack, or freezing and thawing damage that require costly repairs.
Low-permeability concretes in overlays are expected to provide a barrier to the
infiltration of harmful solutions. However, the overlays may develop shrinkage
cracks, facilitating the infiltration of harmful solutions. The purpose of this
project was to demonstrate and evaluate 16 overlay systems for bridge
rehabilitation. In this paper, the 13 overlay concretes are described and the
fresh (air content and slump) and hardened properties (strength, permeability,
and drying shrinkage) are presented. Our report of their condition after 1 year
is based on a visual survey. Conclusions: High performance concrete
overlays that have low permeability to chloride penetration and satisfactory
compressive, flexural, and bond strengths can be constructed with a variety of
combinations of SF, fly ash, S, latex, corrosion inhibiting admixtures, SRA, and
fibers. The concretes with the SRA have the lowest shrinkage values. The
overlays with the polyolefin fibers have a rough surface. Finally, the overlays
are in good condition after 1 year.
Michael M. Sprinkel, Celik Ozyildirim,
PhD., Virginia Transportation Research Council, 530 Edgemont Road,
Charlottesville, VA 22903. Tel: (804)-293-1941 Fax: (804)-293-1990. e-mail: mms2c@virginia.edu
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980440 “Field and Laboratory Evaluation of Silica Fume
Modified Concrete Bridge Deck Overlays in Ohio”
Abstract: The objective of this study was to evaluate, under field and
laboratory conditions, the properties of silica fume modified concrete (SFMC)
mixes that have been used by the Ohio Department of Transportation for bridge
deck overlays since 1984. The research methods included construction monitoring
of nine overlay placement projects, visual inspections of 145 decks, in-depth
condition surveys of 28 decks, and testing of laboratory SFMC mixes using
materials obtained from the construction monitoring projects.
Conclusions: The performance of SFMC overlays in Ohio through 1995 was
generally very good, with none of the existing overlays showing spalling or
patching. Instances of drying shrinkage cracking were noted. Laboratory testing
indicated that the SFMC mixes showed low chloride permeability values and very
high compressive strength values. Recommendations are provided regarding the mix
design and construction specifications, with the intent being to reduce the
potential for drying shrinkage. This paper is not included on the 1998 Preprint
CD-ROM. Please contact author for information.
Michael G. Fitch, Osama A.
Abdulshafi, Department of Civil Engineering, Ohio State University, 470
Hitchcock Hall, 2070 Neil Avenue, Columbus, OH 43210-1275. Tel: (614) 292-4988
Fax: (614) 292-3780. e-mail: fitch.29@osu.edu.
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980514 “Influence of Early Age Volume Changes on Long-Term
Concrete Shrinkage”
Abstract: Volume changes can occur in concrete during the first 24 hours
which are generally missed in laboratory shrinkage evaluations. Unfortunately
these early age volume changes are present in real pavements and structures and
can contribute to the cracking behavior of the concrete at later ages. Early age
volume changes can occur in two forms: drying shrinkage prior to the start of
curing and autogenous volume changes. Expansions have also been identified in
some cases. The purpose of this paper is to present the results of some
investigations of volume changes in concrete during the first 24 hours under
both drying and non-drying conditions. In this study a ring test was used to
evaluate the cracking potential of a concrete mixture due to shrinkage and
tensile strain development. Measured material properties including split tensile
strength, elastic modulus, drying shrinkage, and autogenous volume change were
used to evaluate the cracking potential of the mixtures. Conclusions:
Autogenous volume changes significantly affected the tensile strain capacity of
the concretes in this study. Because the autogenous volume change was expansion,
the tensile strain capacity of these concretes was increased. Many instances of
autogenous shrinkage have been identified in the literature, and this autogenous
shrinkage could significantly reduce the tensile strain capacity of those
concretes. Autogenous volume changes must be considered when evaluating the
cracking potential of a concrete mixture.
Erika E. Holt, Technical Research
Centre of Finland, VTT Building Technology, P.O. Box 1805, FIN-02044, VTT,
Finland. Tel: (358 9) 456-4567 Fax: (358 9) 456-7004. e-mail: ehirow@u.washington.edu. Dr. Donald J.
Janssen, Department of Civil Engineering, University of Washington, Box 352700,
Seattle, WA 98195-2700. Tel: (206) 543-7331 Fax: (206) 543-1543. e-mail: d6423@u.washington.edu.
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981510 “Effect of Water-Cement Ratio on the Early Age Tensile
Strength of Concrete”
Abstract: Cracks develop in otherwise uncracked concrete when tensile
stresses exceed the tensile strength of the material. This is true even in the
first few hours after casting fresh concrete. The authors examined the rate at
which tensile strength develops in recently cast concrete. Conclusions:
The chief difficulty in such studies is in measuring low values of tensile
strength for a viscous, inelastic material. Designing and building appropriate
experimental apparatus for this work became a major portion of the project. It
appears that there is a dormant period from between 2 to about 4 hours in which
tensile strength was immeasurably low. Pragmatically, this corresponds to the
time period in which plastic shrinkage cracking is frequently seen to be
initiated. Tensile capacity developed very rapidly after the dormant period, and
in all cases development of tensile strength was more rapid the lower the
water-cement ratio. This paper is not included on the 1998 Preprint CD-ROM.
Please contact author for information.
Jon Abel, Walter P. Moore and
Associates. Ken Hover, Cornell University, 302 Hollister Hall, Ithaca, NY 14853.
Tel: (607) 255-3406 Fax: (607) 255-9004. e-mail: kch7@cornell.edu.