Concrete containing rice husk ash to sulfate attack

Deterioration of concrete structures in sulfate environments is a well-known phenomenon. Cement chemistry is an important parameter in coping with sulfate attack. C3A and CA (OH)2 lead to expansion, cracking and strength reduction. The use of rice husk ash (RHA) can improve the sulfate resistance of concrete. It was observed that the sulfate resistance of blended cements was significantly higher in sulfate environments. This study investigates the effect of RHA replaced by cement on the durability of concrete due to sulfate attack. Three RHA replacement levels were considered in the study which is 7%, 10% and 15% by the weight of cement. After the specified initial moist curing period (28 days), concrete specimens were immersed in sodium sulfate & magnesium sulfate solution. The degree of sulfate attack was evaluated by measuring the compressive strength reduction of concrete cubes and their weight losses in both continuous immersed and wetting-drying conditions. Expansion observed in the ordinary Portland cement mortar prisms was larger than expansion for the RHA mortar prisms. Moreover, microstructure of the mortar and concrete incorporating Rice Husk Ash were studied through SEM tests.