Overview of Latex Modified Concrete Overlays: Final Report

About the report:

Twelve bridges with latex modified concrete (LMC) overlays ranging in age from new to 13 years were studied and their general condition found to be good. The half-cell and chloride data were inconclusive because background data were not available for the older overlays, but the data should be useful some 5 to 10 years from now if similar data are collected at that time for comparison. The shear strength of the bond between the LMC overlays and the base concretes was about the same or greater than that of the base concrete, which indicates that good bonds were achieved and have been maintained. The permeability to chloride ions based on the rapid permeability test was an average of 773 coulombs (very low) for a 1.25 in. thick LMC overlay and 4,590 coulombs (high) for the base concretes. The inverse of the ratio of the logarithm of the permeability of the LMC overlay to that of the base concrete was 1.27, which provides a very conservative indication of the relative benefits to be obtained from the LMC overlay as compared to an A4 concrete overlay. The three sets of cost assumptions developed indicate that an LMC overlay costs 6% to 31% more than an A4 concrete overlay. Considering that the benefit-to-cost ratio ranged from 0.97 to 1.20, it was concluded that for bridges in which the low permeability provided by the LMC overlay is needed, the benefits usually obtained are worth the extra cost when compared to that of an A4 concrete overlay.

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