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Engineering Properties of Concretes with Combinations of Cementitious Materials

The overall objective of this paper is to establish the engineering properties of concrete containing combinations of fly ash/silica fume and slag/silica fume. Six concrete mixtures were tested, with total cementitious materials content of 350 kg/m cubed and 450 kg/m cubed, and a constant water/cementitious materials ratio of 0.45. The effect of three curing conditions was investigated, and the tests were performed up to about 260 days. The results reflect conclusively that cement replacement materials reduce sightly the engineering properties of portland cement concrete, and that the exposure conditions have a strong influence on flexural strength, dynamic modulus, and ultrasonic pulse velocity. Slag was generally found to be slightly superior to fly ash in the development of these engineering properties. The key to developing fly ash/silica fume and slag/silica fume concretes without suffering a reduction of strength gain when exposed to drying environmental conditions is to incorporate within the mixtures adequate amounts of portland cement and water to ensure the continuation of pozzolanic reactivity and hydration.