ISSN 0862-5468 (Print), ISSN 1804-5847 (online) 

Ceramics-Silikáty 37, (2) 76 - 78 (1993)


PHASE TRANSFORMATIONS DURING HYDROTHERMAL HEATING OF TRICALCIUM ALUMINATE IN LIQUID WATER
 
Šatava Vladimír
 
Institute of the Chemistry of Glass and Ceramic Materials, Czechoslovak Academy of Sciences, Sokolská 38, 120 00 Prague 2

Hydration of the paste of powderec C₃A*) in liquid water was studied by the method of differential hydrothermal analysis over the temperature range of 0-350 °C. The process takes place in two stages. During the first, at temperatures of up to 40 °C, a continuous layer of C₃AH₁₃⁻₁₉ is formed on the surface of C₃A grains, and a layer of the more stable C₃AH₆ at up to 80 °C. At 100 °C, the rate of the reactions falls virtually to zero as a result of slow water diffusion through the layer of the product The second stage starts at 180 °C, producing non-crystalline calcium hydroaluminate with the approximate composition C₁₂A₇Hx, and the process proceeds up to 300 °C until the C₃A has been spent. The share of hydroaluminates formed during the first stage increases with increasing specific surface area of the initial C₃A. The hexagonal aluminates are converted at 130 °C to cubic C₃AH₆ which is then decomposed to C₄A₃H₃ and CH on attaining the temperature of 250 °C.


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