EFFECT OF MgO/MgSO₄ MOLAR RATIO ON THE HYDRATION AND MECHANICAL PROPERTIES OF BMS CONTAINING STEEL SLAG

Abstract

The work aims to investigate the effect of MgO/MgSO₄ molar ratios (MSMRs) on the hydration and mechanical properties of basic magnesium sulfate (BMS) cement and basic magnesium sulfate-containing steel slag (BMS-SS). The exothermic rate and cumulative heat release were monitored, and the hydration products and pore structures were analysed. In addition, the compressive strength was measured. The results show that the hydration process of BMS and BMS-SS are both affected by the MSMRs; samples with an MSMR of 7 have the highest cumulative heat both for the BMS and BMS-SS. A higher MSMR has a negative effect on the formation of 5-1-7 and leads to the formation of Mg(OH)₂. The incorporation of SS leads to the formation of gypsum, especially for the samples with a low MSMR. Both the porosity and its distribution are affected by the MSMR, samples with an MSMR of 5 are significantly higher than those with an MSMR of 7 and 9, and the average pore diameter of the samples with an MSMR of 7 is the lowest whether or not SS is incorporated. The compressive strength of the samples with an MSMR of 7 and 9 are nearly equal and prominently higher than the samples with an MSMR of 5. The SS incorporation leads to a decrease in the compressive strength for all the samples.

Keywords

• basic magnesium sulfate cement
• steel slag
• hydration process
• compressive strength
• pore structures