Evaluation of Silica Fume High Density Thin Bonded Overlays (FHWA-OK-02-2 2132)

Abstract

Aggregate base is an important component of a pavement structure. It supports the asphalt concrete (AC) layer and reduces the wheel load-induced stresses on the underlying Microsilica fume, commonly called silica fume, is made up of particles which are 100 times smaller than those which make up cement. When silica fume is added to Portland Cement Concrete (PCC), its small size allows it to fill voids, producing a denser, less permeable, PCC. In September, 1999, the Oklahoma Department of Transportation (ODOT) experimentally placed overlays of silica fume modified PCC on two bridge decks. The two bridges are located on 1-35 in Carter County. The overlays have been evaluated since placement. Surveys for the evaluation included collecting data from the following tests: Half-cell potentials, smoothness measurements, crack surveys, and general condition surveys. In the three years since the overlays were placed, corrosion activity measured by half-cell potentials has remained low and smoothness measurements have indicated a good ride. Cracking has increased over three years, but cracks have not exceeded "hairline" width. The bridge deck had remained in good condition.