Effect of some heavy metal salts on the formation of ettringite

The effect of the addition of chloride and nitrate salts of Zn, Cu, Pb and Cr on the hydration reaction of a mixture of 3CaO. Al2O3 (C3A) and gypsum with molar ratio 1: 3 was studied. Different ratios of each salt were used namely; 0.5, 2 and 4 % by weight of the solid mixture. Hydration reaction was carried out at 35°C for various time intervals; 1/2 hour, 3, 6 and 24 hours, 3 and 7 days. Hydration kinetics of the system 3CaO. Al2O3 – CaSO4. 2H2O in absence and presence of different salts was studied via the determination of the combined water contents.