The kinetics of the hydration of cement, investigated by an electrical resistance method

Various methods of measuring the initial and final setting time of cements have been proposed and widely used. None of these, however, is satisfactory for a more scientific and fundamental investigation of the hydration process, since the hardening process could not be followed continuously. These indirect and empirical measurements led to many misconceptions on the hydration process and on the effect of accelerators and retarders, etc. The measurement of conductance provides a non-destructive and continuous method for studying the hydration of cements. The kinetics can be described by two parameters: an induction period, t0, and one or two first-order reaction rate constants, k and k′, for the decrease of conductance. The influence of additives on both parameters has been studied extensively.