In 2007, the worldwide production of rice husk was
estimated to be 130 million tons with China and India alone
accounting for more than half of the entire production [5].
This enormous amount of rice husk is difficult to manage in
an effective way primarily because it has very low nutritional
value and cannot be used as animal feed, it takes a long time
to degrade and is not suitable to use as compost [6]. Often
times the rice husk is landfilled or used as a supplementary
fuel in a kiln which in turn generates rice husk ash (RHA).
Depending on the incineration temperature the RHA could
have as much as 80–95% reactive silica When RHA is
mixed with cement and water, it forms calcium silicate
hydrate gel by consuming calcium hydroxide during the
hydration of cement. Saraswathy and Song [8] reported that
incorporating 25% RHA in concrete results in better corrosion
control with reduced chloride penetration, decreased permeability and increased strength. Off-white RHA (OWRHA) which
is considered an improvement over traditional RHA because
it has no crystalline SiO2 or toxic metal can improve concrete
compressive strength, splitting tensile strength and overall
performance just at 15% replacement level [9]. These studies
have demonstrated the effectiveness of RHA in producing
high strength concrete.