Properties of Concrete Containing Low-Calcium Fly Ash Under Hot and Humid Climate

Abstract

This paper reports on the data of setting time, strength, modulus of elasticity, drying shrinkage, and compressive creep of concrete containing a low-calcium fly ash under hot and humid (28 n 2 C, 75 n 15 percent, relative humidity) climate. Tests were carried out for Grade 25 and 35 concretes. The cement replacements with fly ash were 0, 20, and 40 percent, by weight. Between 3 and 90 days under moist curing (28 n 1 C), fly ash concrete gives rise to strength increases of about 110 and 230 percent with the fly ash contents of 20 and 40 percent, respectively, compared to an increase of about 65 percent for the control concrete. The relationship between the modulus of elasticity and compressive strength was not influenced by the partial replacement of cement by fly ash. Both grades of concrete with 40 percent fly ash content and moist cured initially for 7 days showed about 35 percent more drying shrinkage after 90 days of drying than the corresponding shrinkage for the control concrete. However, the shrinkage was found to be about 7 percent lower than that for the control concrete when the initial moist curing period was increased from 7 to 28 days. For Grade 35 concrete, the creep coefficient of concrete with fly ash content of 40 percent was 11 percent lower than that of the control concrete. However, Grade 25 concrete showed a 4 percent higher creep coefficient for fly ash concrete with the same 40 percent fly ash content.