Masonry Magazine April 1997 Page. 20
Know Project Requirements for Mortar
The project specifications and drawings provide a formal communication link between owner needs and the contractor (see Fig.1). The mason contractor must then know what the project specifications and drawings require with respect to mortar(s), mortar submittals, and mortar testing. Since project specifications typically define mortar requirements by using referenced ASTM standards, the mason contractor must know the provisions of those standards as well.
Specification of Mortar
The Standard Specification for Mortar for Unit Masonry, ASTM C 270, provides acceptance criteria for mortar as a component masonry material. It defines four different types of mortars intended to address the variety of needs stemming from different masonry applications. It provides two methods of specifying these mortars, proportion specifications and property specifications. These are separate and distinct methods. It is intended that one or the other be used, not both. If the project specifications do not indicate which method of specifying mortars applies, ASTM C 270 states that the proportion specifications govern unless data are presented to and accepted by the specifier to show that mortar meets the property specifications.
If the proportion specifications are used, acceptance is based on assurance that: (a) component materials meet applicable ASTM product specifications, and (b) job site mortar proportions are controlled to a mix design consistent with the proportion specification table of ASTM C 270 (Table 1). If the property specifications are used, acceptance is made based on assurance that: (a) the component materials meet applicable ASTM product specifications, (b) a laboratory proportioned and mixed mortar using these materials meets the requirements of the property specification table of ASTM C 270 (Table 2), and (c) job site mortar materials are controlled to the proportions of sand and cementitious materials used in the laboratory test mortar. The amount of water used to mix mortar at the construction site is left to the discretion of the mason, with advice that the maximum amount of water consistent with workability be used. This recognizes that a flowable, workable mortar is more important to performance than the measured compressive strength of the mortar as a separate component masonry material. Figure 2 summarizes how ASTM C 270 is organized.