The installation and condition of the first two very-early-strength latexmodified concrete (LMC-VE) overlays constructed for the Virginia Department of Transportation are described. The overlays were prepared with a special blended cement rather than with the Type I/II cement used in the conventional latex-modified concrete (LMC) overlay. LMC-VE mixture proportions, installation equipment, and procedures are similar to those used for conventional LMC overlays. However, when working with LMC-VE, the contractor must work faster because the concrete loses slump rapidly and the curing period is approximately 3 rather than 72 hours. Tests of the compressive strength of the LMC-VE overlay performed during the early hours after installation indicated that traffic could be placed on the overlay within 3 hours rather than within the 4 to 7 days required for the conventional LMC overlay. Tests of bond strength and permeability to chloride ion indicated that the overlays are performing satisfactorily and can be used as an alternative to LMC to extend the life of bridge decks. Pending continuing favorable test results, it is anticipated that LMC-VE overlays can be used when construction during short lane-closure periods is highly desirable. The use of LMC-VE may reduce inconvenience to motorists, allow for installation at night, provide negligible to very-low permeability, and provide high strength, particularly high early strength.

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Thin concrete overlays are widely used to protect decks against corrosion caused by the infiltration of chloride ions. These overlays are designed to have low permeability and to be free of cracks that may adversely affect the performance of the deck by facilitating the penetration of chloride ions. Sixteen high-performance concrete overlays with 13 concrete mixtures placed on two bridges were evaluated, with an emphasis on shrinkage characteristics. One overlay was constructed with concrete containing a new shrinkage-reducing admixture. Specimens prepared with this admixture had the lowest shrinkage. Based on a visual survey, all overlays were performing satisfactorily at 1 year after placement.

The opinions, findings, and conclusions expressed i11 this report are those of the author and not 1111cessarily those of tire spo11sorin 11ge11cies.