LAUSR

Egyptian magnesite was used in the preparation of some SiC-magnesium oxychloride (MOC) paste composites for application as grinding stones. The bulk density, compressive strength, abrasion resistance and dissolution in water of the grinding stones were evaluated and compared to those of industrially produced samples. The prepared MOC paste samples were also investigated by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) to elucidate the changes in their functional groups and microstructure, respectively. Four MOC cement paste samples with a MgO/MgCl2 molar ratio of 7/1 and different H2O/MgCl2 molar ratios of 11, 13, 15 and 17 were prepared. Due to the increased water content, their bulk density, compressive strength and abrasion resistance decreased; however, their dissolution in water increased. Moreover, a gradual enhancement in the formation of phase 5 [5 Mg(OH)2·MgCl2·8H2O] was followed by FTIR spectroscopy. Furthermore, a greater amount of phase 5 with larger crystals was embedded in a relatively porous structure, as detected by SEM technique. The grinding test samples were prepared by incorporating 30 mass% fine SiC powder in the MOC cement pastes. It was found that this strongly improved the bulk density, compressive strength, abrasion resistance and dissolution in water of the prepared samples. It was also found that nearly all of the properties of the samples prepared in this study are superior to those of the industrially produced grinding stones.