Solid solution and hydration behaviour of magnesium-bearing tricalcium silicate phase

Saturation solubility of MgO in tricalcium silicate (C3S) and the hydration kinetics of magnesia-bearing tricalcium silicate phase have been studied. MgO-doped C3S was obtained by repeated firing of calcium carbonate and quartz in the stoichiometric ratio of 3:1 in the presence of varying amounts of MgO from 0.5 to 5% by weight. Elemental analysis and X-ray diffraction studies have revealed that up to 1.5% MgO goes in solid solution at 1450 degrees C and the rest precipitates as periclase. Presence of 1% MgO marginally slows down the rate of hydration of tricalcium silicate up to about 20 h and then increases sharply to overtake the hydration rate of pure C3S. Complete hydration could be achieved in 28 days for the doped sample, against 83% for the undoped C3S in the same period. The study has been found useful in understanding the relationship between modified chemical/mineral composition and the hydration behaviour of magnesia-doped C3S phase. (C) 1998 Elsevier Science Ltd.