Early-age hydration kinetics of polymer-modified cement

The hydration kinetics of styrene butadiene rubber latex-modified cement have been studied by isothermal conduction calorimetry. The influence of factors such as polymer concentration, polymer modification, presence of surfactant and alkalinity of cement have been investigated. It has been found that the polymer acts as a retarder first by increasing the induction time, thus suppressing the nucleation of cement hydration products, and secondly by restraining the growth of these phases during the acceleration stage. Reaction rate constants for the acceleration stage have been calculated using modifications of the Jander and Avrami equations and activation energies have been estimated. Small concentrations of polymer were found to influence the growth of phases to a substantial degree but not to change the hydration mechanism. In contrast, larger concentrations of polymer influenced the induction time and changed the hydration mechanism.