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ASTM C618
The American Society for Testing and Materials (ASTM) is probably the most widely recognized and used national standards-setting organization in the United States for engineering-related materials and testing. The ASTM C618 specification is the most widely used because it covers the use of fly ash as a pozzolan or mineral admixture in concrete. The three classes of pozzolans are Class N, Class F, and Class C. Class N is raw or calcined natural pozzolan such as some diatomaceous earths, opaline cherts, and shales; tuffs, volcanic ashes, and pumicites; and calcined clays and shales. Class F is pozzolanic fly ash normally produced from burning anthracite or bituminous coal. Class C is pozzolanic and cementitious fly ash normally produced from burning lignite or subbituminous coal. The table below shows the chemical and physical requirements listed in the ASTM C618 specification.
