This report summarizes the 5-year study to evaluate the long-term performance of the overlays. Two types of concrete overlays (silica fume concrete (SFC) and latex-modified Type III portland cement concrete (LMC-III) were installed and tested as part of the Strategic Highway Research Program (SHRP) Project C-206: Optimization of Highway Concrete Technology—Bridge Deck Overlays. The two different overlay types were chosen for their ability to fill two different needs: use of SFC as a long-term, low-permeability overlay; and use of LMC-III as a high early-strength concrete for use when traffic had to be restored after as little as 24 hours.

Evaluation and comparison of SFC and LMC-III overlays were performed at four locations. The test sites were in Ohio and Kentucky. Each location included SFC and LMC-III overlays on opposite directions of a bridge structure. All overlays were installed in 1992. This study evaluated the overlays each year between 1994 and 1998. All overlays had high initial bond strengths, and the bond strengths remained high over the study period when tested away from delaminations. The overlays were generally rated as good condition in 1998, after 6 years of service, though some individual sites were rated as fair due to extensive cracking. Though good performance was achieved from both SFC and LMC-III overlays, the service life of the overlays tended to vary based on the site location. Generally, cracking and delamination of the overlays tend to increase with time. Typically, all overlays should be inspected biannually for cracking and delamination and routine maintenance including consideration of crack and delamination repairs to extend the service life of the SFC and LMC-III overlays.