The resistance to high temperature of magnesia phosphate cement paste containing wollastonite

This paper aims to study the effect of wollastonite addition on the behavior of magnesium ammonium phosphate cement (MAPC) and magnesium potassium phosphate cement (MKPC) pastes exposed to different high temperatures. Different dosages of wollastonite were added to replace MgO powder in these two types of magnesia phosphate cements. The paste specimens were exposed to 105 degrees C for 24 h and to different temperatures of 200, 400, 600, 800 and 1000 degrees C for 3 h and then cooled to room temperature for different tests including mass loss, visual appearance, compressive strength, mineral composition and microstructure observation. The results show that the specimens containing 10 % wollastonite for both MAPC and MKPC mixtures presents the most improved high temperature resistance due to the excellent heat stability of wollastonite mineral and the refined microstructure. And the addition wollastonite has little influence on the hydration products of these two magnesia phosphate cements. Therefore, the incorporation of wollastonite is a potential method to improve the heat- resistance of MAPC or MKPC.