Thermal property evolution and prediction model of early-age low-heat cement concrete under different curing temperatures

The evolution of low-heat concrete thermal properties is controlled by microstructure growth and affects the early-age mass concrete structure cracking under real curing conditions from the perspective of heat transfer. In this paper, experiments were carried out to obtain the evolution of the hydration heat, thermal conductivity, specific heat capacity, and microstructure of different water-binder low-heat mortars under different curing temperatures. The results show that all the thermal property variation rates are sensitive and positive to the curing temperature. The hydration rate increases with increasing water-binder ratio, and the thermal conductivity and specific heat capacity mainly decrease with increasing hydration degree, but the thermal conductivity has a brief and rapid increase stage when the hydration degree is less than approximately 0.38. At the same curing time, the thermal conductivity is higher with a higher waterbinder ratio, and the specific heat capacity is inverse. The microstructure results show that the porosity, pore size distribution curve, and threshold pore size decrease with increasing age and curing temperature and increase with increasing water-binder ratio. Meanwhile, the relations between microstructure and thermal property evolutions also show that thermal properties have an exponential positive correlation with porosity, and their variations are controlled by hydration products and pore water due to the variable hydration process. In addition, based on the results and hydration kinetics, a multiscale thermal parameter prediction model of low-heat concrete considering curing temperature and the water-binder ratio was established by the method of theoretical deduction.