DURABILITY OF SILICA FUME CONCRETE EXPOSED TO CHLORIDE IN HOT CLIMATES

The premature deterioration of reinforced concrete structures is a serious problem in hot coastal environments. Most of this deterioration is caused by chloride ingress through the concrete, resulting in the corrosion of the reinforcing steel. Since the mid 1990s the practice of specifying silica fume in concrete has widened in the Middle East, as engineers work to improve the durability of concrete, which is subjected to the extreme exposure conditions in the region. Current practice is to use mixtures with a maximum water/cement ratio of 0.4 and to replace 5% to 10% of the cement with silica fume depending on the degree of exposure. Are these small amounts of silica fume sufficient to maintain an appropriate life span for concrete structures under the varying exposure conditions, and how much cover is required to the reinforcement to protect the steel from corrosion? In this paper, models are proposed to estimate the chloride ion ingress into portland cement concrete and silica-fume-enriched concrete under different exposure conditions. The results show that small amounts of silica fume are sufficient as long as appropriate concrete covers to reinforcement are maintained and chloride exposure to the concrete is correctly assessed.