Evaluation of Magnesia Cement Using MgCO3 and Serpentine

Abstract

MgO based cement for the low-temperature calcination of magnesite required less energy and emitted less CO 2 than the manufacturing of Portland cements. Furthermore, adding reactive MgO to Portland-pozzolan cement can improve their performance and also increase their capacity to absorb atmospheric CO 2 . In this study, the basic research for magnesia cement using MgCO 3 and magnesium silicate ore (serpentine) as starting materials was carried out. In order to increase the hydration activity, MgCO 3 and serpentinite were fired at a temperature higher than 600 o C. In the case of MgCO 3 as starting material, hydration activity was highest at 700 o C firing temperature; this MgCO 3 was completely transformed to MgO after firing. After the hydration reaction with water, MgO was totally transformed to Mg(OH) 2 as hydration product. In the case of using only MgCO 3 , compressive strength was 35 kgf/cm 2 after 28 days. The addition of silica fume and Mg(OH) 2 led to an enhancements of the compressive strength to 55 kgf/cm 2 and 50 kgf/cm 2 , respectively. Serpentine led to an up to 20% increase in the compressive strength; however, addition of this material beyond 20% led to a decrease of the compressive strength. When we added MgCl 2 , the compressive strength tends to increase.Key words magnesia cement, MgO, hydration activity, compressive strength, MgCl 2 . 서 론시멘트