Phase transformation and hydration of dicalcium silicate containing stabilizers

Abstract

β-dicalcium silicate was stabilized at room temperature and synthesized from reagent grade chemicals using B2O3, K2O or SO3 as stabilizers. B2O3 acts as the most effective stabilizer for dicalcium silicate. Phase transformation from β- to γ-dicalcium silicate depends on the start temperature of quenching. Hydration heat of β-C2S shows that SO3 delayed hydration at an early hydration time, but higher heat liberation rate at a later hydration time than the other stabilizers. 29Si MAS NMR analysis shows that the hydrate of dicalcium silicate stabilized by B2O3 is polymerized more than those of dicalcium silicates stabilized by K2O and SO3. Dicalcium silicate presents different shapes of calcium silicate hydrate according to stabilizers: dicalcium silicate stabilized by B2O3 shows crumbled foil shape and K2O needle shape of C-S-H.