Influence of glycerin grinding aid on the compatibility between cement and polycarboxylate superplasticizer and its mechanism

Abstract

The glycerin (GL) is commonly used as a grinding aid component in cement production, however it can bring poor compatibility between cement ground with it (GL-C) and polycarboxylate superplasticizer (PCE), which causes difficulties to construction. This paper studied the influence and its mechanism of GL on the compatibility between cement and PCE. Since grinding effect of GL is an important part of the influence mechanism, it is also investigated in detail in this paper. The surface properties of cement particles, PCE adsorption capacity and heat flow curve of cement hydration were tested. The fluidity and its loss of cement paste were measured as manifestations of compatibility. Results show that GL-C has good compatibility with PCE when the dosage of GL does not exceed 0.02%. This is because GL optimizes the particle size distribution of cement and increases the adsorption capacity of PCE, together with the retarding effect of GL. And when the dosage of GL ranges from 0.01% to 0.02%, the grinding and retarding effects of GL decreases the fluidity loss of cement paste. As the dosage increases, GL shows significantly negative influence on the compatibility between GL-C and PCE when the dosage does not exceed 0.04%. This is because the continuously decreasing surface energy and adhesive work of GL-C reduce the adsorption capacity of PCE sharply, and the grinding and retarding effects are not so influential to compatibility as a lower dosage of GL. In addition, results also indicate that the fluidity always decreases from 5 min to 60 min after water addition, while the adsorption capacity of PCE increases.