This specification pertains to admixtures for masonry mortars. Admixtures are substances other than the prescribed materials of water, aggregate, and cementitious materials that are used to improve one or more of the recognized desirable properties of conventional masonry mortar. Admixtures are classified by their effect on the performance characteristics of conventional masonry mortars. Admixed mortars are classified by their modified properties, as compared to a reference mortar. The following classifications are recognized: bond enhancer, workability enhancer, set accelerator, set retarder, and water repellent. The materials to be used include Portland cement, hydraulic cement, blended hydraulic cement, masonry cement, mortar cement, lime, and sand. Different test methods shall be implemented in order to determine the following properties: soluble chloride content, compressive strength, water retention, air content of plastic mortar, board life, time of setting, flexural bond strength, and rate of water absorption.

1.1 This specification pertains to admixtures for masonry mortars. Admixtures are substances other than Specification C270 prescribed materials of water, aggregate, and cementitious materials that are used to improve one or more of the recognized desirable properties of conventional masonry mortar.

1.2 This specification does not cover coloring pigments.

Note 1: Information on coloring pigments can be found in Specification C979.

1.3 This specification does not cover additives that are added to the cementitious materials during the manufacture of the cementitious materials.

1.4 Acceptance of an admixture is based on its performance in an admixed mortar. Acceptance of the admixed masonry mortar is based on attainment of performance either equivalent to that required for conventional mortar or improved performance of one or more indicated properties, while maintaining required performance levels for other properties.

1.5 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.

Note 2: The testing laboratory performing the test methods referenced in this specification should be evaluated in accordance with Practice C1093.

1.6 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.