Influence of chloride ion on the hydration reaction of C3A in presence of gypsum and lime

Abstract

The hydration reactions of the systems C3A, C3A + gypsum (1 : 1.5 mole ratio) and C3A + gypsum + lime (1 : 1.5 :1 mole ratio) in 0.1 and 1 molar solutions of sodium chloride at room temperature are studied. The hydration products formed after 2 min and up to 7 days were investigated using X-ray diffraction analysis. The filtered solutions were also analysed for sulphate, chloride, aluminium and calcium contents and the pH values of these solutions were determined. X-ray diffraction analysis indicated the formation of chloro-compound known as Friedel's salt in all the studied systems. The ettringite phase and Fridel’s salt appeard in systems containing gypsum and lime. Increasing concentration of NaCl solution increased the rate of formation of both compounds.