Features of cement paste hydration and hardening processess with the addition of hydrated cement

The article is about application calorimetry method for influence investigation of the additive of pre-hydrated cement slurry (PHC) on cement hydration. Pre-hydration of the cement lasted 2, 4, 6 hours with forced mixing at W/C equal to 0.7. The results of heat measurement were obtained by using a simple calorimeter. The test was carried out for 28 hours. It is shown that the addition of PHC2-10%, PHC4-10% and PHC6-10% leads to an offset the peak of heat generation by 1.5, 2.4, 2.5 hours earlier. It is concluded that this additive leads to intensification of heat generation and, consequently, affects the hydration of cement, as well as the prop-erties of cement paste and stone. The obtained conclusions about the acceleration of hydration, setting time and hardening cement paste are correlated with earlier tests of strength and setting time.