Isothermal calorimetry tests and modeling of cement hydration parameters

Degree of cement hydration can be characterized by hydration parameters including activation energy (Ea) and hydration curve parameters (ultimate hydration degree αu, hydration shape parameter β, and hydration time parameter τ). These parameters are affected by material compositions including chemical and mineral admixtures. In this study, isothermal calorimetry tests were performed at different ambient temperatures with cement mortar mixtures with different amounts of water reducers and fly ashes. Hydration model was used to back-calculate hydration parameters using the measured heat generation–time relationship. Results showed that the activation energy Ea generally increases with increasing water reducer dosage and fly ash replacement. Hydration curve parameter αu seems to decreases, while τ generally increases with increasing water reducer dosage and fly ash replacement, and β seems to increase with increasing water reducer dosage. As a result, the simulated temperature developments in the early-age concrete pavement showed that increased water reducer dosage and fly ash replacement results in decreased pavement temperature, thus reduced thermally-induced stress.