This specification covers lightweight aggregates intended for use in concrete masonry units when a prime consideration is to reduce the density of the units. Three general types of lightweight aggregates are covered by this specification: aggregates prepared by expanding, palletizing, or sintering products such as blast-furnace slag, clay, diatomite, fly ash, shale, or slate; aggregates prepared by processing natural materials such as pumice, scoria, or tuff; and aggregates consisting of end products of coal or coke combustion. The aggregates shall be composed predominately of lightweight-cellular and granular inorganic material. The aggregates shall not contain excessive amounts of deleterious substances, as determined by organic impurities, staining, and loss on ignition tests. Lightweight aggregate under test shall meet requirements for clay lumps and friable particles, uniformity of grading, loose bulk density, uniformity of loose bulk density, popouts, resistance to freezing and thawing, and drying shrinkage.