Magnesium oxysulphate cements

The three major types of oxysalt bonded AB cement are the zinc oxychloride, the magnesium chloride and the magnesium oxysulphate cements. The bases employed, therefore, are either zinc oxide or magnesium oxide, both of which readily undergo hydration in aqueous solution, behaving as M(OH)2 species and acting as a source of hydroxyl ions. They are thus both clearly bases in the Bronsted-Lowry sense. 

A detailed study of the phase relationships in the magnesium oxysulphate cement was carried out by Urwongse Sorrell (1980b). They used X-ray analysis to examine the phases present in the cement, and established the composition of the invariant liquids after equilibration by measuring specific gravity with the aid of a pycnometer. Specific gravities were related to concentration by means of a calibration exercise in which 30 stock solutions of sulphuric acid at concentrations between 0 and 79-5 wt % were prepared with distilled water. 

Beaudoin, J. J. Ramachandran, V. S. (1978). Strength development in magnesium oxysulphate cement. Cement and Concrete, 8 (1), 103-12. 

Ellis, H. Fire barrier coating composition containing magnesium oxychlorides and high alumina calcium aluminate cements or magnesium oxysulphate, US Patent 4,572,862. 

---