Investigation on the Compressive Strength of Concrete with Microsilica Additive under Different Durations of Accelerated Steam Curing

The purpose of this research is to conduct a laboratory study to investigate the effect of using microsilica additive on the compressive strength of concrete under different durations of accelerated steam curing. For this aim, four mix designs have been considered, in which in two of them microsilica additive is used in the amount of 10% and 15% by weight of cement. 48 cubic samples were cured by immersion in water and their compressive strength was measured at the ages of 3, 7, 14, and 28 days. Also, 84 cubic samples were subjected to accelerated steam curing under the maximum temperature of 66±2 ºC and their compressive strength was measured after 4, 8, 16, 24, 32, 40, and 48 hours of treatment. The research results show that by adding microsilica to concrete, the ultimate compressive strength increases in both types of curing. Calculating the ratio of the strength of the samples under steam curing to the corresponding value in water curing indicates that the designs with microsilica have weaker performance than the designs without microsilica in terms of gain rate in compressive strength. Also, the results show that with the reduction of the water-cement ratio, concrete strength setting in steam curing occurs faster. Finally, it is suggested that if microsilica powder is used in concrete as an additive, in order to provide 70% of the 28-day strength of concrete, which is necessary for producing prefabricated and prestressed concrete, microsilica powder must be used in the amount of 15% by weight of cement and concrete must be subjected to steam treatment for 24 hours.