Field and Laboratory Evaluation of Silica Fume Modified Concrete Bridge Deck Overlays in Ohio

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 were evaluated under field and laboratory conditions. The research methods included construction monitoring of 9 overlay placement projects, visual inspections of 145 decks, in-depth condition surveys of 28 decks, and testing of laboratory SFMC mixes with materials obtained from the construction monitoring projects. Notable activities included field-testing to compare the effectiveness of ground-penetrating radar and manual sounding techniques for detecting the presence of debonded/delaminated deck areas and laboratory testing of overlay bond strength specimens under direct tensile loading. Based on the information collected, it was concluded that the overall performance of SFMC overlays in Ohio through 1995 was good, with none of the existing overlays showing spalling or patching; however, instances of drying shrinkage cracking were noted. Recommendations are provided to assist in achieving optimum SFMC overlay performance.