This specification covers gypsum, calcium sulfate combined with two molecules of water in crystalline form. If necessary, gypsum shall be crushed or ground, or both, to the size specified. Different test methods shall be performed in order to determine the chemical composition and physical properties of gypsum.

1.1 This specification covers gypsum, calcium sulfate combined with two molecules of water in crystalline form and having the approximate chemical formula CaSO₄·2H₂O.

1.2 The values stated in either inch-pound units or SI (metric) are to be regarded separately as the standard. Within the text, the SI units are shown in brackets. The values stated in each system shall be used independently of the other. Values from the two systems shall not be combined.

1.3 The text of this specification references notes and footnotes which provide explanatory material. These notes and footnotes (excluding those in tables and figures) shall not be considered as requirements of the specification.