This Blended hydraulic cements are produced by intergrinding or blending Portland cement and supplementary cementitious materials such as fly ash. The use of blended cements in ready-mix concrete reduces mixing water and bleeding, improves workability and finishing, inhibits sulphate attack and the alkali-aggregate reaction, and reduces the heat of hydration. Depending on the constituents, blended cements can confer desirable qualities to concrete such as lighter colour, workability, or low heat of hydration. Slag from steel making and fly ash from the power industry are two commonly added materials in blended cements. By putting waste to work, blended cements contribute to sustainable development.