EVALUATION OF AN 8-YEAR-OLD SILICA FUME CONCRETE BRIDGE DECK OVERLAY

摘要

This paper describes the investigation of a bridge deck overlay repair. This particular location experiences approximately 50 freeze/thaw cycles annually; the average annual application of deicing salt is estimated at 30 kg/m~2. The bridge was repaired in 1986 and 1987 by overlaying one lane with a dense concrete without silica fume and the other lane with a silica fume concrete. Both overlays were placed by the same contractor using the same equipment and techniques. The quality of both repairs was high. After more than eight years in service, both overlays are performing well, with very little abrasion and good resistance to frost damage. ASTM C 1202 test results show the silica fume concrete to have very low chloride penetrability, while the dense concrete has moderate to low chloride penetrability. Chloride profiles confirm that the silica fume concrete has been more effective in limiting the migration of chloride ions. The microstructure of the silica fume concrete appears sound through the full thickness of the overlay. The concentration of chlorides near the upper surface was significant. The microstructure and microanalysis are consistent with the excellent performance of the concrete in the field.