Continuously monitoring the early hydration process of cement paste at elevated temperatures by a developed non-contact resistivity measurement apparatus

The early hydration process of cementitious material at elevated temperatures was studied by a specially developed non-contact resistivity measurement apparatus (NCRMA). By using NCRMA, the relationship between elevated curing temperature (20, 40, 60, and 90°C) and the early hydration process of cement paste with low water-binder (w/b) ratio was found. Results indicate that the early hydration process of low w/b cement pastes cured in 60 and 90°C consists five stages: the dissolving stage, competition stage, acceleration stage, the transformation of AFt to AFm stage, and steady hardening stage. However, the transformation of AFt to AFm stage was not found in the condition of 20 and 40°C. Besides, the increase in curing temperature leads to a short duration of the dissolution stage and a decrease of ultimate electrical resistivity value. In addition, in the range of 20 to 40°C, with the increasing of curing temperature, the duration of the competition stage decreases. However, this situation is reversed when the curing temperature is between 40 and 90°C. It is suggested that the hydration process is retarded at a higher temperature.