Durability properties of concrete with silica fume and rice husk ash

The present investigation explores the durability properties of concrete incorporated with silica fume (SF) and rice husk ash (RHA) as the replacements of Portland slag cement (PSC). PSC cement is selected for the study owing to its superior characteristics compared to other types of cement. Two groups of concrete mixes are considered in which SF and RHA are used as 5%, 10% 15% and 20% of PSC separately and properties are compared with the control mix having only PSC cement. Durability properties like acid resistance, rapid chloride permeability, carbonation resistance, transport test (water sorptivity, porosity and water permeability) of concrete are evaluated to deduce the effect of SF and RHA on the concrete matrix. In relation to the process of hydration, the behavior of RHA is observed to be different from SF. With 15% replacement SF and RHA, the 28 days concrete compressive strength is enhanced by 23.6% and 20.3%, respectively with reference to the control mix. However, the 90 days concrete strength becomes 31.7% and 30.95% higher than that of control mix. In terms of durability properties, the trend displayed by RHA is also very much similar to the SF concrete. The hydrated concrete samples are examined for the microstructural characteristics by the scanning electron microscopy (SEM). The microstructural changes caused by the improved reactivity of admixture and densification are associated with the improvement in the concrete characteristics. Finding from this experimental study suggest that the RHA has immense potential to significantly reduce the cost of concrete rather than SF, in rice producing Asian countries.