The Early Hydration Characteristics of Portland Cements with Superplasticizer Using Electrical Measurements

Abstract

In this paper, an electrical measurement was applied to investigate the early hydration characteristics of cement paste with different dosages of superplasticizer. The bulk electrical resistivity development curves and the derivative curves were studied. It is found that there are two main peaks and four critical points on the derivative curves. The critical points are used to divide the hydration process into dissolution, setting, acceleration, deceleration and diffusion-controlled periods. The physical meanings of the critical points are identified by the penetration measurement of Vicat device and the heat evolution test. The setting occurred in the second period which provides an alternative method to determine the setting time by the electrical measurement. The results of the bulk electrical resistivity have a positive relation with that of the compression strength. The retardation effect of the superplasticizer is demonstrated by the delayed time for the critical points occurrence and confirmed by the setting time. A rapid method for selecting a suitable dosage of the chemical admixture for construction requirements is proposed.