Durability of microsilica concrete, subjected to Arabian Gulf exposure

Premature deterioration of reinforced concrete structures is a serious prob lem in the Arabian Gulf. Much of this deterioration is caused by chloride i ngress through the concrete, which results in the corrosion of the reinforc ing steel. Over the last 5 years, the practice of specifying microsilica in concrete has widened, as engineers work to improve the durability of concr ete, which is subjected to the severe exposure conditions in the region. Cu rrent practice is to use microsilica additions ranging from 5% to 10% depen ding on the degree of exposure. Are these amounts of microsilica sufficient to maintain a realistic life span for concrete structures? How much micros ilica is really needed to provide durable concrete with an appropriate life under the varying exposure conditions? In this paper, models are proposed to estimate the chloride ion ingress into Portland cement concrete and micr osilica enriched concrete under different exposure conditions. The results show that small amounts of microsilica are sufficient as long as appropriat e concrete covers to reinforcement are maintained and chloride exposure to the concrete is correctly assessed.