6.4 Lightweight Aggregates—The procedures for specific
gravity, absorption, and preparation of aggregates mentioned in
this practice pertain to materials with normal absorption
values. Lightweight aggregates, air-cooled slag, and certain
highly porous or vesicular natural aggregate may be so
absorptive as to be difficult to treat as described. The moisture
content of lightweight aggregate at the time of mixing may
have important effects on properties of freshly mixed and
hardened concretes such as slump loss, compressive strength,
and resistance to freezing and thawing