微量のCaOを添加したMgO-SiO₂系クリンカーの反応機構

抄録

The mechanism of reaction in MgO-SiO₂ and MgO-SiO₂-CaO systems is investigated in this paper. The following two series of experiments have been practiced; 1) Mixture of MgO powder (99.9%) and quartz grains (99.99%, 150-300 μm), and 2) Mixture of MgO powder, quartz grains and additional 0.4% of CaO were heated at the temperatures between 1400°C and 1600°C. In MgO-SiO₂ system, Mg²⁺ ion diffused into quartz grains to form reaction layers of forsterite and thin layers of enstatite when heated below 1500°C. When the sample was heated above the eutectic temperature (1543°C) of the system, forsterite was observed on both sides of quartz and sintered MgO. These facts suggest that the liquid, which is formed in between enstatite and quartz, penetrates through forsterite into sintered MgO. As the result, SiO₂ component removes from quartz and then gaps or pores are formed in quartz grains. Finally quartz grains are replaced the vacant pores. In MgO-SiO₂-CaO system, forsterite was observed inside sintered MgO and an opening of gaps in quartz grains begins at a temperature as low as 1400°C. This suggests the liquid phase occures at the temperature as low as 1400°C when the third component, CaO, is added. The phases supposed to be liquid in the reaction layers were analysed EP-MA. The fact that the analysed data roughly coincide with the composition of ternary eutectic liquid will strongly support the above assumption.