Early-age hydration mechanism of ternary binders: Quantitative relation between microstructure evolution and strength build-up

The goal of this study is to develop a better understanding of the working mechanisms of CACC$ acceleration of OPC in the first hour and establish a quantitative link between the progress of hydration, strength build-up and associated microstructure evolution. Monitoring the progress of reaction using isothermal calorimetry in the first few minutes of hydration is difficult owing to the limitations associated with the measurement method. We have developed a method to correct the heat data in the first minutes, which along with ICP data of elements Ca, Al and S, enables a quantification of the amounts of various phases dissolving and/or precipitating at different times after acceleration. It is concluded that strength build-up is directly proportional to heat of hydration up to a certain point, irrespective of accelerator dosage. However, beyond this point, there is a change of mechanism which is likely attributed to physical effects rather than chemical ones. Additionally, it was also found that the amount of available CA controls the rate of reaction and that the impact of CAC addition to OPC follows a decay function type heat release.