ASTM C563-18a

3.1 The purpose of this guide is to estimate the SO_{3.2 The SO3 content of a cement giving maximum performance is different at different ages, with different performance criteria and with different materials such supplementary cementitious materials and chemical admixtures. A manufacturer can choose the performance criteriato determine optimum SONote 1: Typically, the optimum SO3 content is higher the later the age.}

3.3 This guide indicates optimum SO_{3.4 It should not be assumed that the optimum SO3.5 The guide is applicable to cements specified in Specifications C150/C150M, C595/C595M, and C1157/C1157M.}

1.1 This guide describes the determination of approximate optimum SO₃ for maximum performance as a result of substituting calcium sulfate for a portion of the cement.

1.2 This guide refers to the sulfur trioxide (SO_{1.3 Values stated as SI units are to be regarded as standard.}

1.4 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.