Improved mechanical strength of magnesium oxysulfate cement using ferric sulfate

Abstract

This research investigated the impact of ferric sulfate addition on the mechanical strength of magnesium oxysulfate (MOS) cement. Variations in the fluidity, setting time, hydration reaction, volume stability, water resistance, phase composition, and microstructure of MOS cement were reported. The results show that the addition of ferric sulfate accelerated the dissolution of MgO through reacting with OH− to form Fe(OH)3 gel and promoting the growth of 3 Mg(OH)2·MgSO4·8H2O, which reduced the fluidity and shortened the setting time of MOS cement. Although the growth time for 5 Mg(OH)2·MgSO4·7H2O was extended after adding ferric sulfate, the content and crystallinity of 5 Mg(OH)2·MgSO4·7H2O were increased, improving the mechanical strength and volume stability of MOS cement. The formation of Fe(OH)3 gel in MOS cement densified the matrix and optimized the pore structure, which can further enhance the mechanical strength and water resistance of MOS cement.