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A latex-modified concrete overlay was placed on Interstate 5 in Northern California at a Strategic Highway Research Program SPS-6 test site. The objective of the test was to evaluate a potentially lower cost latex overlay system. The cost of the overlay would be reduced by eliminating surface prewetting and the wet burlap cure. The test section was placed 300-m long across three lanes. Unusual features of the overlay were: (1) it was placed on a dry substrate, (2) latex content was 43% higher than conventional practice, (3) cure was by curing compound rather than wet burlap, and (4) it was on a plain jointed portland cement concrete pavement. Bond to the substrate was very good. Curing compound provided an adequate curing membrane when applied at the proper rate. The system was evaluated annually. To date, the only problem has been at the joints, which present a serious problem for a bonded overlay. Delaminations or spalls have occurred at most of the transverse joints. The objective was met although the system is not suitable for use on jointed pavements.
A latex-modified concrete overlay can be placed on a dry substrate and bond well. It can also be cured successfully with a curing compound that conforms to Specification for Liquid Membrane-Forming Compounds for Curing Concrete (ASTM C 309), Type 2, Class B. This type of overlay is not suitable for a jointed pavement without careful attention to the joint detail.
Senior materials and research engineer, California Department of Transportation, Sacramento, CA
Stock #: CCA10144J