Thermal Decomposition of Hydrocalumite over a Temperature Range of 400-1500 degrees C and Its Structure Reconstruction in Water

The thermal decomposition process and structure memory effect of hydrocalumite were investigated systematically for the first time over a wide temperature range of 400-1500 degrees C. The calcined hydrocalumite samples and their rehydrated products were characterized by XRD, FT-IR, and SEM-EDX. The results show that the calcination products at temperatures ranging from 500 to 900 degrees C are basically mayenite and lime, while one of the final products obtained by calcination at and above 1000 degrees C is probably tricalcium aluminate (Ca3Al2O6). For the hydrocalumite samples calcined at temperatures below 1000 degrees C, their lamellar structure can be completely recovered in deionized water at room temperature. However, the further increase of calcination temperature could impair the regeneration ability of hydrocalumite via contact with water. Upon calcination of hydrocalumite at 1000-1500 degrees C followed by reaction with water, a stable compound tricalcium aluminate hexahydrate (Ca3Al2O6 center dot 6H(2)O) was produced, which is the reason why less hydrocalumite could be regenerated.