Production of monetite-based Inorganic Phosphate Cement (M-IPC) using hydrothermal post curing (HTPC)

A new hydrothermal post curing (HTPC) technique is developed in this study to overcome the long term evolutions such as shrinkage and cracking of Inorganic Phosphate Cement (IPC). HTPC is based on thermally induced transformation of the unstable calcium phosphates phases, e.g. brushite and amorphous calcium phosphate (ACP), into more stable phases, e.g. monetite, with prevention or minimization of the bulk shrinkage during the treatment. To achieve this effect, sufficient pore moisture is kept in IPC during the transformation stage. This way, the increase of skeletal density thus does not necessarily lead to significant global bulk shrinkage, since the contraction of the skeleton is replaced internally by an increase of the pore size. This effect can be obtained by post curing in the autoclave, when a sufficiently high temperature is used to provoke the necessary structural transformation, combined with a pressure high enough to force the pore moisture and the released bound water to stay inside the pores. After evaluation of this technique, it was noticed that the monetite percentage in the hydrothermally post cured IPC products increases from 26% to 39%, compared to the heated reference IPC. It is also verified that additional pore volume replaced the bulk shrinkage that would occur when IPC is heated without autoclave pressure. This new modified IPC end product is called monetite-based IPC (M-IPC). (C) 2010 Elsevier Ltd. All rights reserved.