This paper summarises the experimental installation of a concrete bridge deck overlay containing silica fume (SF). The minimum thickness of the overlay was specified as 1.25 In. The objective was to determine whether concretes containing silica fume can be successfully used in thin overlays as a cost-effective alternative to the widely used latex-modified concrete (LMC). A two-lane, four-span bridge deck was overlaid with concrete containing silica fume at 7 percent or 10 percent by weight of the portland cement as an additional cementitious material. The concrete was mixed in a truck mixer rather than a continuous mixer (which is used for LMC), but otherwise the placement procedures established for LMC were applied to concretes with SF. Concretes with 7 percent or 10 percent SF exhibited satisfactory strengths and would be rated as having very low chloride permeability as determined by AASHTO method T 277. The resistance of these concretes to cycles of freezing and thawing were satisfactory when air content was within specification. Performance of the sf concrete will be monitored for a period of at least 5 yr to evaluate the durability of the overlay.
Abstract