hydration of C3A systems in sodium chloride solutions

This study attempts to generate information about the chemistry of the hydration reaction of tricalcium aluminate [C3A] in 0.1 M sodium chloride solutions for hydration times up to one week at room temperature. The effect of gypsum, lime and alite on the progress of the reaction was investigated and the behavior of the dissolved ions was related to that of the solid phases. It is found that the hydration of C3A in 0.1 M sodium chloride solutions, also in the presence of gypsum, lime and alite has shown quite modification compared to that in water. The calcium chloro aluminate hydrate is a major phase formed in the different systems. It appears as a sole hydration product during the hydration of C3A alone in sodium chloride solutions, shows up together with ettringite phase in the presence of gypsum and predominates the ettringite phase in the presence of lime and alire. The hydration rate and the consumption of C3A in sodium chloride solution occur faster in the presence of gypsum than that in the presence of lime and alite

Effect of gypsum additions on the hydration of tricalcium aluminate at 30 degree

The hydration of the tricalcium aluminate in presence of different amounts of gypsum in excess water has been studied from 2 min to one week at 30 degree by means of X-ray diffraction as well as the chemical methods of analysis. The sulfate ion concentration in the bulk solution increases with increasing gypsum content. It remains constant during the first 15 min then decreases with the formation of ettringite which maximum is reached around three hours at an almost total drop of the sulfate ion concentration. The concentration of aluminium is depressed by the presence of sulfate. It passes through a minimum after 15 min then increases up to one week. At early hydration stage the monophases appear beside the ettringite. They become the predominant phases after the ettringite maximum with the simultaneous consumption of the unreacted tricalcium aluminate. The complete conversion of ettringite to the low sulfate form is retarded in mixtures of originally high sulfate content