ASTM C563 - 13

    Standard Test Method for Approximation of Optimum SO3 in Hydraulic Cement Using Compressive Strength

    Active Standard ASTM C563 | Developed by Subcommittee: C01.28

    Book of Standards Volume: 04.01


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    Significance and Use

    3.1 The purpose of this test method is to estimate the SO3 content for a hydraulic cement that gives maximum compressive strength in mortar made and cured at 23 °C. The value obtained is one way to establish an appropriate level of sulfate in the manufacture of cements specified in Specifications C150, C595 and C1157.

    3.2 The SO3 content of a cement giving maximum compressive strength is different at different ages of mortar; typically this SO3 content is higher at 3 days than the 24-h, and often higher for 7 days than that for 3 days. A manufacturer can choose the age of 24-h, 3 days or 7 days for specimens at which to determine optimum SO3 content.

    3.3 This test method indicates optimum SO3 content for cement in mortar made and cured at a standard temperature of 23.0 ± 2.0 °C (73.5 ± 3.5 °F). The optimum SO3 increases with increasing temperature and may increase when water-reducing admixtures are used.

    3.4 It should not be assumed that the optimum SO 3 estimated in this test method is the same SO3 content for optimum performance of a concrete prepared from the cement.

    3.5 The test method is applicable to cements specified in Specifications C150, C595, and C1157.

    1. Scope

    1.1 This test method describes the determination of approximate optimum SO3 for maximum compressive strength at 24 h, 3 days, or 7 days by measuring the change in strength produced in hydraulic cement mortar as a result of substituting calcium sulfate for a portion of the cement.

    1.2 This test method refers to the sulfur trioxide (SO3) content of the cement only. Slag cements and occasionally other hydraulic cements can contain sulfide or other forms of sulfur. The determination of SO3 content by rapid methods may include these other forms, and may therefore produce a significant error. If a significant error occurs, analyze the cement for SO3 content using the reference test method of Test Methods C114 for sulfur trioxide.

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


    2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    ASTM Standards

    C109/C109M Test Method for Compressive Strength of Hydraulic Cement Mortars (Using 2-in. or [50-mm] Cube Specimens)

    C114 Test Methods for Chemical Analysis of Hydraulic Cement

    C150 Specification for Portland Cement

    C204 Test Methods for Fineness of Hydraulic Cement by Air-Permeability Apparatus

    C305 Practice for Mechanical Mixing of Hydraulic Cement Pastes and Mortars of Plastic Consistency

    C471M Test Methods for Chemical Analysis of Gypsum and Gypsum Products (Metric)

    C511 Specification for Mixing Rooms, Moist Cabinets, Moist Rooms, and Water Storage Tanks Used in the Testing of Hydraulic Cements and Concretes

    C595 Specification for Blended Hydraulic Cements

    C778 Specification for Sand

    C1157 Performance Specification for Hydraulic Cement

    C1437 Test Method for Flow of Hydraulic Cement Mortar


    ICS Code

    ICS Number Code 91.100.10 (Cement. Gypsum. Lime. Mortar)

    UNSPSC Code

    UNSPSC Code 30111601(Cement)


    DOI: 10.1520/C0563-13

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