Optimum Mixture Proportions for Concretes Containing Fly Ash and Silica Fume

About the report:

Concretes with equal water/cement ratios and equal paste volumes of various combinations of cement, fly ash, and silica fume were tested to establish parameters for strength and chloride permeability. Comparative specimens with Type II and Type III cement were tested. The effects of temperature and moisture availability during curing were also evaluated. In general, the laboratory tests showed that, when adequate curing in the 73°F to 100 °F temperature range is provided, concretes with satisfactory early and 28-day strengths and good resistance to chloride ion penetration can be obtained with either type of cement and various combinations of fly ash and silica fume. The cementitious material can be in the range of 30 to 35 percent fly ash and 5 percent silica fume, based on the weight of the cementitious material. Similar specimens cured at 43°F generally did not develop an adequate early strength, and the chloride permeability was high. Combinations of the pozzolans with Type III cement yielded higher strengths and a lower chloride permeability than did similar combinations with Type II cement.

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