1.1 This specification covers blended supplementary cementitious materials that result from the blending or intergrinding of two or three ASTM compliant supplementary cementitious materials, for use in concrete or mortar where hydraulic or pozzolanic action, or both, is desired. The supplementary cementitious materials include slag cement conforming to Specification C989, natural pozzolans and coal fly ash conforming to Specification C618 and silica fume conforming to Specification C1240. 1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. NOTE 1—The incorporation of supplementary cementitious materials as separate additions or as a manufactured blend may significantly alter the properties of fresh and hardened concrete. The user should be aware of these changes and is referred to the ACI Manual of Concrete Practice2 for information and guidelines. Specific reference is made to: ACI 232.1R Use of Natural Pozzolans in Concrete ACI 232.2R Use of Fly Ash in Concrete ACI 233R Slag Cement in Concrete and Mortar ACI 234R Guide for the Use of Silica Fume in Concrete 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.