Evaluation on steel bar corrosion embedded in antiwashout underwater concrete containing mineral admixtures

摘要

This study aims the evaluation of the corrosion of steel bar embedded in antiwashout underwater concrete, which has rather been neglected to date. To that goal, accelerated steel bar corrosion tests have been performed for three series of steel bar-reinforced antiwashout underwater concrete specimens manufactured with different admixtures and under different environments. The three series of antiwashout underwater concrete were: concrete constituted exclusively by ordinary portland cement (OPC), concrete composed by ordinary portland cement mixed with fly-ash in 20 percent ratio (FA20) and concrete with ground granulated blast furnace slag is mixed in 50 percent ratio (BFS50). And, the three different environments were: manufacture in the air, in tap water, and in artificial seawater. results using half-cell potential surveyor showed that, among all the specimens, steel bar in OPC manufactured in artificial seawater was the first one that exceeded the threshold value proposed by ASTM C 876 with a potential value below -350 mV after 14 cycles. And, the corresponding corrosion current density and concentration of water soluble chloride were measured as 0.3 muA/cm~2 and 0.258 percent. On the other hand, for the other specimens that are FA20 and BFS50, potential values below -350 mV were observed later at 18 and 20 cycles, respectively. Results confirmed the expectation that mineral admixtures may be more effective in delaying the development of steel bar corrosion in antiwashout underwater concrete.