The Effects of Prehydration on the Liquid Hydration of 3CaO·Al2O3 with CaSO 4·2H2O |
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Authors: | ELSE BREVAL |
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Affiliation: | F. L. Smidth Laboratories, DK-2500 Valby, Denmark |
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Abstract: | Liquid hydration and water-vapor hydration of 3CaO·Al2O3, were studied. Variable parameters were hydration time, temperature, relative humidity, and amount of gypsum. The hydration products (gel, ettringite, hexagonal hydrates, and 3CaO·Al2O3·6H2O) were studied by electron microscopy, X-ray diffractometry, and thermal analysis. A reaction scheme is proposed. The degree of water-vapor hydration influenced the sequence of the subsequent liquid hydration which, however, was independent of the composition of the water-vapor hydration products. Below a critical degree of water-vapor hydration (?3% combined water) the reaction with liquid water occurred as if no water-vapor hydration had taken place. Above this value the reaction gave hydration products suggesting a change of the 3CaO·Al2O3 reactivity. A possible correlation with the retardation of strength development of prehydrated cement is suggested. |
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