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 <TEX>$CO_2$</TEX> 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 <TEX>$CO_2$</TEX>. In this study, the basic research for magnesia cement using <TEX>$MgCO_3$</TEX> and magnesium silicate ore (serpentine) as starting materials was carried out. In order to increase the hydration activity, <TEX>$MgCO_3$</TEX> and serpentinite were fired at a temperature higher than <TEX>$600^{\circ}C$</TEX>. In the case of <TEX>$MgCO_3$</TEX> as starting material, hydration activity was highest at <TEX>$700^{\circ}C$</TEX> firing temperature; this <TEX>$MgCO_3$</TEX> was completely transformed to MgO after firing. After the hydration reaction with water, MgO was totally transformed to <TEX>$Mg(OH)_2$</TEX> as hydration product. In the case of using only <TEX>$MgCO_3$</TEX>, compressive strength was 35 <TEX>$kgf/cm^2$</TEX> after 28 days. The addition of silica fume and <TEX>$Mg(OH)_2$</TEX> led to an enhancements of the compressive strength to 55 <TEX>$kgf/cm^2$</TEX> and 50 <TEX>$kgf/cm^2$</TEX>, 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 <TEX>$MgCl_2$</TEX>, the compressive strength tends to increase.