Risk of chloride-induced corrosion of steel in SF concrete exposed a chloride bearing environment

Abstract

The present study concerns the resistance of silica fume (SF) concrete against chloride-induced corrosion, when SF concrete is built in a chloride-bearing environment. Chloride transport and critical chloride threshold level were experimentally obtained, which were subsequently used for the Fick’s 2nd law to calculate the corrosion-free life. As a result, it was found that SF concrete had lower chloride transport in terms of the apparent diffusion coefficient, due to a refinement of the pore structure, resulting from a further formation of C-S-H gel in the cement matrix. Simultaneously, the surface chloride for SF concrete had a slightly lower range, arising from the lower capacity to bind chlorides. However, SF mortar imposed the increased corrosion risk. The chloride threshold for SF mortar accounted for 0.45% by weight of binder, while OPC produced 0.96%. Despite the increased corrosiveness in SF concrete, SF concrete produced the longer corrosion-free life, compared to OPC. From the sensitivity analysis, a reduction of the parametric values on chloride transport in SF concrete could significantly increase the corrosion-free life. For example, the apparent diffusion coefficient for SF concrete was about 74% reduced compared to OPC concrete, and thus the time to corrosion was 270% increased.