Rice husk ash (RHA) is agricultural waste from the factory, the ash obtained by the burn and will get grayish color on the natural burning. Rice husk ash contain silica SiO2 90%-95% and get by burning by temperature 600 - 700 derjat celcius.
in Concrete RHA good for pozzolanic reaction whit cement and will make good workabily then can make compressive strength concrete.
Reference :