Effects of alkalies on hydration of β-dicalcium silicate and its resultant hydrates

Abstract

β-dicalcium silicate was synthesized and hydrated with/without alkalies at different temperatures. Alkalies accelerated the hydration of β-C2S and influenced the polymerization of calcium silicate hydrate. KOH and NaHCO3 caused excessive and early liberation heat of the β-C2S. The effect of NaHCO3 was more significant than that of KOH on the acceleration of hydration. The curing temperature was also an important factor in the acceleration of the hydration of β-C2S; the hydration was occurred much more actively at 40°C than at 20°C. The controlled β-C2S showed a much greater degree of polymerization of calcium silicate hydrate than did the alkali-added β-C2S. The hydrates of β-C2S were influenced by alkalies and temperature. The controlled β-C2S showed needle-like and wide needle-like shapes of calcium silicate hydrates, while the alkalic-added β-C2S presented long and wide needle-like shapes and crumbled foil-like shapes of calcium silicate hydrates. The calcium silicate hydrates formed at high temperature exhibited also crumbled foil-like shapes.