Thermal behavior of cement matrix with high-volume mineral admixtures at early hydration age

摘要

Thermal cracks that usually occur in mass concrete are closely related to the thermal behavior of cement matrix, such as heat liberation, temperature rise and thermal shrinkage. Cement pastes added with large-volume mineral admixtures that are usually used for thermal controlling were cast into well-sealed plastic cylinder and covered by heat insulation materials to simulate the pseudo-adiabatic condition of mass concrete. The deformation and temperature rise of cement specimens under the heat insulation condition have been examined at early hydration age. Results show that with addition of fly ash, coal gangue and blast furnace slag the heat liberation and peak temperature of cement paste decrease, while its total shrinkage increases. There is no shrinkage but expansion of the pastes during the temperature rise process, which may be ascribed to the complete compensation of the shrinkage by thermal dilation of the pastes. The thermal dilation coefficient (TDC) of cement paste changes drastically with the hydration duration, and it is also related to the addition of mineral admixtures.