ABSTRACT
ASTM C 618, Standard Specification for Fly Ash and Raw or Calcined Natural Pozzolans for Use as a M ineral Ad mixture in Portland Cement Concrete, covers the follow ing three classes of mineral admixtures:
Class N: Raw or calcined natural pozzolans such as diatomaceous earth, opaline chert, tuffs, volcanic ashes (pumicite), and calcined clays or shales.
