ASTM International Standard Specification for Mortar for Unit Masonry ASTM C270-25b

This specification covers mortars for use in the construction of non-reinforced and reinforced unit masonry structures. Four types of mortar are covered in each of two alternative specifications: (1) proportion specifications and (2) property specifications. The property specification applies to mortar mixed to a specific flow in the laboratory. When neither proportion nor property specifications are specified, the proportion specifications shall govern, unless data are presented to and accepted by the specifier to show that mortar meets the requirements of the property specifications. This specification does not cover the determination of mortar strengths through field testing. The compressive strength values resulting from field tested mortars do not represent the compressive strength of mortar tested in the laboratory nor that of the mortar in the wall. Physical properties of field sampled mortar shall not be used to determine compliance to this specification and are not intended as criteria to determine the acceptance of rejection of the mortar. Compliance to this specification is verified by confirming that the materials used are as specified, meet the requirements as given, and added to the mixer in the proper proportions as described.