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.

Composites of gadolinium-doped ceria/magnesia(CGO/MgO) were synthesized and characterized for the electrolytes of intermediate temperature solid oxide fuel cells. XRD and SEM results revealed that composite electrolytes consisted of their own phases after sintering at 1400˚C without noticeable solid solution of Mg into CGO. As the MgO content increased, the total electrical conductivity decreased, which might be attributed to the decrease of grain boundary conductivity, possibly due to the lowering of the continuity of the CGO grains and blocking effects of the insulating MgO phase. The space charge effect may not be a significant factor to affect the electrical conductivity of the CGO/MgO composites.

마그네시아-지르코니아 복합체의 소결과 미세구조에 미치는 TiO2의 영향에 대하여 검토하였다. 3mol%Y2O3를 함유한 ZrO2는 TiO2첨가시 1400˚C에서 기지상인 MgO와 첨가제인 TiO2의고용에 의해서 c-ZrO2상으로 존재하였다. TiO2첨가시 조성에 관계엾이 승온수축거동은 유사하였으며 1650˚C에서 최종수축율은 8.58-11.0%였다. 1.67wt%TiO2첨가시 소결이 촉진되어 1600˚C 2시간에서의 소결밀도는 3.7g/cm3(이론밀도의 98%)였다. ZrO2내에 고용된 MgO와 TiO2의 양은 각각 5.67wt%, 2.62wt%로 냉각과정중 입계주위에서 일부 석출되어 Ti화합물을 형성하였다. 이의 존재로 말미암아 생성된 미세균열은 꺽임강도를 감소시켰다.

This paper was evaluated biological properties of Magnesia cemntitious composites using SAP as a basic study for development to biological panels. Biological properties were evaluated for pH, moisturizing, and surface roughness.

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.

한중콘크리트 공사에 적용을 검토할 수 있는 초속경 콘크리트는 초기 급속한 발열반응을 통해 동해를 입기 전에 소요의 강도를 확보할 수 있을 것이며, 열 보상을 통해 시공환경이 유지될 경우 강도발현에 필요한 시간을 단축할 수 있는 장점이 있다. 일반 콘크리트는 영하의 기온에서 타설할 경우 양호한 경화를 얻을 수 없으며, 저온에서 동해를 방지하고 경화성을 확보하기 위하여 내한방동제를 첨가하여 사용하고 있다. 그러나, 내한방동제의 대부분은 염화물을 주성분으로 하고 이를 다량으로 사용할 경우, 콘크리트의 동결을 방지하고 시멘트의 수화반응을 촉진시켜 응결시간을 단축하고 초기강도 증진을 유도하는 효과가 있는 반면, 장기재령에서 강도발현이 문제가 되고, 경제성이 떨어진다는 단점이 있다. 최근 연구되고 있는 마그네시아 인산염 복합체는 초속경성이 있고 저온에서도 수화반응이 가능한 것으로 보고되고 있어 새로운 한중공사 및 극한지용 건설재료로 사용할 수 있을 것으로 판단된다. 따라서, 본 연구에서는 한중공사 및 극한지에서 사용이 가능한 건설재료의 개발을 위한 사전 연구의 일환으로서, 마그네시아 인산염 복합체를 활용한 모르타르에 대해 온도의 영향을 고려한 재료 물성 평가를 실시하고 적정 배합을 제안하고자 한다.