engleski

Trermal analysis of calcium aluminate cement hydration products

Hydration of calcium aluminate cement (CAC) had been investigated with the aim of development of mathematical model of hydration. By means of combined differential scanning calorimetry and thermogravimetric analysis (DSC/TGA) and X-ray powder diffraction (XRD) the data are obtained about the composition and dehydration behavior of hydrated samples that are compared with the results of other authors. In the early ages of hydration, metastable products are formed: CAH10, C2AH8* and alumina gel that slowly converts into the stable hydration products: C3AH6 and g-AH3, gibbsite. Composition and the rate of the conversion of metastable hydration products depend on temperature and time. During the hydration the crystallinity of hydration products increases what is accompanied by the increase of the temperature of the maximum rate of decomposition reaction. The empirical dependence of the peak temperature on the hydration time is established. Dehydration of C2AH8 in the temperature interval of 80-100oC is heavily overlapped with the temperature interval of dehydration of CAH10 and alumina gel. Complexity of several-stage decomposition of calcium aluminate hydrates and aluminum hydroxide prevents quantitative analysis of hydrated material.

calcium aluminate cement; hydration; DSC/TGA; XRD

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