1.1 This specification covers special aggregates for use in radiation-shielding concretes in which composition or high specific gravity, or both, are of prime consideration. 1.2 The values stated in SI units are to be re This specification covers special aggregates for use in radiation-shielding concretes in which composition or high specific gravity, or both, are of prime consideration. Aggregates covered by specification include the natural mineral aggregates of eith