Ceramics-Silikáty 58 (4) 275-281 (2014)

THERMAL PROPERTIES OF A SUSTAINABLE CEMENT MATERIAL: EFFECT OF CURE CONDITIONS

This paper presents the effect of cure temperature and cure time on the thermal properties of wollastonite-based calcium phosphate cement, a sustainable cement material. Mass losses of 11.7 % at 105 - 220°C and 1.8 % at 380 - 500°C in TGA experiment were attributed to brushite to monetite and monetite to calcium pyrophosphate conversion, respectively; which was further confirmed by FTIR. TGA results also indicated that the mass loss can be minimized by increasing curing time and decreasing curing temperature. Deformation values recorded from the first heating cycle of TMA results revealed a linearly decreasing trend with increase in curing time. CTE values, as obtained from the second heating cycle of TMA results remained more-or-less constant with variation in curing time and slightly increased with increase in cure temperature, possibly due to change in moisture content. From the (exothermic) DSC curves, the rate of hydration at different cure temperatures were evaluated using the linear slope in the accelerating period of cement hydration and the data was matched with a model-free Freidman analysis. The activation energy was found to be 57.8 kJ∙mol^-1.

Keywords: Calcium phosphate cement, Curing, Cement hydration, Thermal properties, Activation energy