Evaluation of a low temperature hardening Inorganic Phosphate Cement for high-temperature applications

Phase and mechanical changes of Inorganic Phosphate Cement (IPC) are identified along with changes in macro properties as functions of temperature and time. In addition to amorphous calcium phosphate (ACP) and amorphous silica, the presence of significant amounts of brushite and wollastonite in the reference specimens of IPC is confirmed using X-ray diffraction. The thermal behaviour of IPC up to 1000°C is varied, but may be categorised into several regions of behaviour exhibited by the specimens. It is found that contraction of the solid phase in IPC due to chemical transformations, e.g. brushite to calcium pyrophosphate, causes reduction in the volume of the material. Also the ongoing meta-stable calcium phosphate transformations and reactions over a long time contribute significantly to the phase instability of the material at ambient conditions. It is found that the strength of IPC increases with ageing at ambient conditions, but the formation of microcracks below 105°C causes a sharp reduction in the mechanical performance of IPC at elevated temperatures. According to the results obtained by Mercury intrusion porosimetry (MIP), the pore system of the reference IPC is dominated by mesopores. With heating up to 150° C, it is observed that the macropore percentage of IPC increases as a result of thermally induced shrinkage.

Publication year:2011

Keywords:brushite, shrinkage, ageing, inorganic phosphate cement