Effect of Molar Ratios on Compressive Strength of Modified Magnesium Oxysulfate Cement

To determine the effect of molar ratios on compressive strength of magnesium oxysulfate cement (MOS), the hardened MOS cement pastes mixed with different molar ratios of MgO/MgSO4 and H2O/MgSO4 were tested on the compressive strength. The examinations of strength development, phase compositions and microstructure of MOS cement are discussed in detail. The results show that these starting materials can significantly affect the compressive strength of MOS cement. The mixture with higher molar ratio of MgO/MgSO4 and lower molar ratio of H2O/MgSO4 can produce more 5Mg(OH)2 ·MgSO4·7H2O(517 phase) and less Mg(OH)2, which benefits the compressive strength of MOS cement.