A Field Investigation of a Concrete Overlay Containing Silica Fume on Route 50 over Opequon Creek

About the report:

This study evaluated concretes containing silica fume for use in overlays as a suitable 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 mass of the Portland cement as an additional cementitious material. The results of laboratory tests on field concretes containing silica fume were satisfactory. Silica fume concrete (SFC) bonds well with the base concrete and has very low permeability, high strength, and satisfactory freeze-thaw resistance. In the field, over the 5-year evaluation period, cracking and increases in half-cell potentials and chloride content indicated a tendency to corrosion. However, such increases are also evidenced with LMC overlays. Thus, the results indicate that SFC can be effectively used in thin overlays as an alternative to LMC. SFC, as LMC, is prone to plastic shrinkage; therefore, immediate and proper curing must be provided to avoid the shrinkage cracking that can occur under adverse curing conditions.

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