Castable matrix, additives and their role on hydraulic binder hydration

The influence of alumina-based castable matrices, dispersants and Li2CO3 on the hydration process of different hydraulic binders was evaluated. The experiments were followed by temperature measurements with the time, the oscillatory rheometry technique and the normal force during the penetration of a blade through the material’s surface. By doing these tests, the chemical features of binder hydration, working and demolding time of suspensions could be assessed. The experiments have shown that the alumina-based matrix presented an accelerating effect which is related to its sodium content. Citric acid and ammonium citrate were the dispersants with the highest delaying effect and could be effectively associated with the accelerator (Li2CO3) in order to adjust the setting time of the suspensions. Nonetheless, their accelerating and retarding effect varied according to the hydraulic binder.