Effect of rice husk ash fineness on the chemical and physical properties of concrete

The influence of grinding on the physical properties of rice husk ash (RHA) and Portland cement is examined. The optimum rice husk ash grinding time (i.e. to produce a highly reactive product with minimum grinding energy) was determined. Eight different fineness grades of rice husk ash were examined and it was found that rice husk ash ground for the optimum grinding time had a median particle size of 9·52 μm. A rice husk ash dosage of 15% by weight of binder was used throughout the experiments. It was found that the specific gravity and the fineness of the rice husk ash increase with an increase in grinding time. However, the morphology of the rice husk ash changed with grinding. There appears to be an optimum grinding time of approximately 90 min, during which time the compressive strength and strength activity index increase significantly. The use of rice husk ash ground for 90 min (to 9·52 μm particle size) produced concrete with good strength and low porosity.