Cement is the most expensive constituents of the concrete. Over 5% of global CO2 emission is attributed to cement production. In this work alternative source for cement as rice husk ash is used. A comparative study is carried on properties of concrete when cement is partially replaced with rice husk ash. Percentage replacement of cement with RHA is varied as from 10%, 15% and 20% with silica fumes kept as constant at 10%. Silica fumes are very reactive pozzolan and are considered having higher durability and strength inhibiting properties which may contribute to attaining the required characteristic properties of concrete. The compressive strength is found at 7 and 28 days. The strength is then compared to standard concrete and the optimum percentage of replacement of RHA is found out.