There are two different types of specifications for cement. Prescriptive specifications restrict the composition of cement or its constituents by giving chemical or physical requirements or limiting the raw materials used. Performance specifications give performance requirements only. Both ASTM C 150 (for portland cement) and ASTM C 595 (for blended hydraulic cement) have prescriptive elements. In 1992 the first performance-based specification for blended cements, ASTM C 1157, was issued. The article includes a table that compares features of the three cement specifications.