Effect of sulphate content of cement upon heat evolution and slump loss of concretes containing high-range water-reducers (superplasticizers)

Abstract

Synopsis At normal temperatures (25°C), concretes containing superplasticizers lose much of their initial high workability within approximately 45 minutes from initial mixing. When the concrete is hot (40°C), the effect is more severe with significant workability (slump) loss occurring within 30 minutes. In this study, the optimum range of SO3, contents for an ordinary Portland cement, with and without superplasticizer addition, has been determined at these two temperatures by using a conduction calorimeter and Lerch's criteria for optimum SO3 content. Concretes were manufactured at both temperatures using cements with the as received and modified SO3 contents, identified in the calorimeter study. It is concluded that there is an optimum range of SO3 content for which workability loss is minimized for concretes containing the superplasticizer, both at the normal and at the elevated temperature. In addition, short- and long-term strengths are improved.