Influence of metal chloride salts on calcium aluminate cement hydration

In this paper the influence of alkali, alkaline earth and transition metals in the form of chlorides salts on the hydration of commercial iron-rich calcium aluminate cement (CAC) is investigated. The effect on setting time and mechanical properties is studied. The results of the setting time obtained from the measured temperature evolution of cement pastes are compared to standard Vicat needle measurements. Addition of alkali metal salts both accelerates the setting time of CAC and deteriorates long-term strengths in the order of decreasing ionic radius of the metals. The effect of alkaline earth metal salts on setting behaviour depends on the amount of addition: low concentrations retard, but high concentrations accelerate setting behaviour. Calcium is found to have the strongest acceleration effect with the lowest deterioration in strength. An interesting regularity is observed when plotting the results of both retarded setting times and strengths against atomic number of added transition metal cation.