Rheology of superplasticized cement paste and concrete subjected to high temperature and prolonged mixing time

Abstract

The rheological properties of fresh cement paste and concrete incorporating polycarboxylate- based superplasticizer were investigated as a function of the mixing time, temperature, and superplasticizer dosage. Cement paste and concrete mixtures were continuously agitated for up to 110 minutes after mixing using low shear rate mixers under controlled temperature ranging from 22 to 45o C. The rheological testing was performed using an advanced shear-stress/shear-strain controlled cement paste rheometer and a BML concrete rheometer, respectively. The test results indicate that the Bingham constants of cement paste and concrete are significantly affected by changes in temperature, mixing time and superplasticizer dosage. Results also suggest that polycarboxylate-based superplasticizers should be used at a dosage close to the saturation in order to ensure adequate rheological behavior at high temperature and prolonged mixing time. The findings of this study are of practical significance and provide guidance on the use of superplasticizers in hot weather conditions. Superplasticizers have been generally developed in countries with mild climates. Hence, current technical information on their use is often unreliable when transposed to extreme hot weather conditions.