1.1 ,This specification covers the quality and grading of the following materials for use in the construction of subbase, base, and surface courses: sand-clay mixtures, gravel, stone or slag screenings, sand, crusher-run coarse aggregate consisting of gravel, crushed stone, or slag combined with soil mortar, or any combination of these materials. The requirements are intended to cover materials having normal specific gravity, absorption, and gradation characteristics. Where other materials are to be used, appropriate limits suitable to their use must be specified.