Cement extenders such fly ash, slag and silica fume can dramatically reduce the rate of corrosion of reinforcing steel in cracked concrete. The presence of a transverse crack in reinforced concrete specimens, subjected to cycles of wetting and drying with a chloride solution to simulate a marine environment, resulted in rapid initiation of corrosion of the steel at the location of the crack. The initiation period was essentially negated and active corrosion started within a few weeks of testing. The protection afforded the embedded reinforcing steel was the increase in resistivity of the concrete, associated with the inclusion of cement extenders, which resulted in a reduction in the overall rate of corrosion.
