The carbon dioxide(CO2) released while producing building materials is substantial and has been targeted as a leading contributor to global climate change. One of the most typical method to reducing CO2 for building materials is the addition of slag and fly ash, like pozzolan material, while another method is reducing CO2 production by carbon negative cement development. The MgO-based cement was from the low-temperature calcination of magnesite required less energy and emitted less CO2 than the manufacturing of Portland cements. It is also believed that adding reactive MgO to Portland-pozzolan cements could improve their performance and also increase their capacity to absorb atmospheric CO2. In this study, the basic research for magnesia cement using MgCO3 and magnesium silicate ore (serpentine) as main starting materials, as well as silica fume, fly ash and blast furnace slag for the mineral admixture, were carried out for industrial waste material recycling. In order to increase the hydration activity, MgCl2 was also added. To improve hydration activity, MgCO3 and serpentinite were fired at 700 oC and autoclave treatment was conducted. In the case of MgCO3 as starting material, hydration activity was the highest at firing temperature of 700 oC. This MgCO3 was completely transferred to MgO after firing. This occurred after the hydration reaction with water MgO was transferred completely to Mg(OH)2 as a hydration product. In the case of using only MgCO3, the compressive strength was 3.5MPa at 28 days. The addition of silica fume enhanced compressive strength to 5.5 MPa. In the composition of MgCO3-serpentine, the addition of pozzolanic materials such as silica fume increased the compression strength. In particular, the addition of MgCl2 compressive strength was increased to 80 MPa.

MgO based cement for the low-temperature calcination of magnesite required less energy and emitted less CO2 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 CO2. In this study, the basic research for magnesia cement using MgCO3 and magnesium silicate ore (serpentine) as starting materials was carried out. In order to increase the hydration activity, MgCO3 and serpentinite were fired at a temperature higher than 600˚C. In the case of MgCO3 as starting material, hydration activity was highest at 700˚C firing temperature; this MgCO3 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 MgCO3, compressive strength was 35 kgf/cm2 after 28 days. The addition of silica fume and Mg(OH)2 led to an enhancements of the compressive strength to 55 kgf/cm2 and 50 kgf/cm2, 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 MgCl2, the compressive strength tends to increase.

This study investigates strength development of magnesia-phosphate cement considering curing temperature and W/B ratio. The results revealed that it showed an excellent strength development at early ago and the influence of curing temperature was within 25% on strength.