Effect of B2O3 on Hydration Behavior of Calcium Aluminate Cement

The hydration behavior of calcium aluminate cements in the presence and absence of B2O3 was investigated. The hydration rate of these two cements was determined via the exothermic temperature development of cement pastes. The dissolution-precipitation rates of the cement aqueous suspensions were evaluated by means of electrical conductivity. The cement hydration was terminated via vacuum freeze drying, and the resultant hydration products were analyzed by X-ray diffraction. The setting behavior of the mortars was determined by a Vicat apparatus, and the flow values of the castables containing the cements were measured on a vibration table. The results indicate that the presence of B2O3 in the cement shortens the induction period of the cements and accelerates the massive precipitation of the hydrates. B2O3 contained in the cement promotes the cement hydration rate, reduces the setting time of the mortar and leads to the flow decay of the castable.