Combinations of Pozzolans and Ground, Granulated Blast-furnace Slag for Durable Hydraulic Cement Concrete

About the report:

Hydraulic cement concretes were produced using pozzolans and ground, granulated, blast-furnace slag (slag) to investigate the effect of these materials on durability. The pozzolans used were an ASTM C 618 Class F fly ash with a low lime content and a dry, densified silica fume. The slag was an ASTM C 989 Grade 120 material. Concretes with a fixed cementitious materials content of 377 kg/m 3 and water-to-cementitious materials ratio (w/cm) were produced with an ASTM C 150 Type I/II cement and pozzolans or slag. The following replacement levels were used: fly ash: 0, 15, 25, and 35 percent; silica fume: 2.5, 5, and 7 percent; and slag: 25, 35, 50, and 60 percent. Concretes were also produced by combining small amounts of silica fume with small amounts of fly ash or slag. The concretes were evaluated for strength, electrical resistance (ionic transport, permeability), drying shrinkage, resistance to freezing and thawing, and resistance to alkali-silica reaction (ASR)-related expansions. Early-age strengths and resistance to freezing and thawing were compromised by high replacement levels of fly ash or slag, although the use of a constant w/cm may have exaggerated these responses. Concrete durability, as indicated by electrical resistance and resistance to ASR, was greatly improved by increasing the pozzolan or slag content. Use of ternary blends produced the desired property levels while maintaining the necessary durability characteristics.

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