The change in reactivity of silicate anions during the hydration of calcium silicates and cement

Abstract

The change in reactivity of the silicate anion complex of tricalcium silicate, β-dicalcium silicate and portland cement during hydration was studied by measuring the rate constant ( k ) of the silicomolybdic acid formation. The three anhydrous starting materials have identical k values indicating their identical monosilicate anion structure. During hydration the value of k decreases continuously; the rate of decrease of k is highest in case of cement and lowest in case of β-dicalcium silicate. The decrease of k can be attributed to the formation of bridging oxygen ions in the silicate complex. k tends to reach a final, limiting value; beyond this k can still be decreased by special techniques as e.g. by regrinding and rehydrating the hardened samples.