Answer by Rakshita Nagayach:
Rice Husk Ash (RHA) is an economical as well as an effective substitute for OPC in concrete. RHA is highly pozzolanic material. The non crystalline silica and large specific surface area of the RHA is responsible for its high pozzolanic activity.
Researchers have investigated the effect of rice husk on pozzolanic
behavior of rice husk ash. They studied the actual range of temperature required to burn rice husk to get the desired pozzolanic product. They investigated that up to 40% replacement of cement with RHA can be made with no significant change in the compressive strength as compared to the controlled mix, if the rice husk is burnt under optimum temperature condition.
RHA produced from agro waste can be used as partial replacement of ordinary Portland cement in cement mortar pastes. Test results show that if approximately 10% of cement is replaced by equal amount of RHA, there is not any significant depreciation in the compressive strength. Thus the RHA can be used as partial replacement of cement in the regions where the material is locally available.