基于微细观结构优化和剩余MgO转化提升碱式硫酸镁水泥耐水性的研究

经化学外加剂改性碱式硫酸镁水泥（BMSC）力学强度和耐水性显著提高，是一种具有极大发展潜力和良好应用前景的绿色胶凝材料。但浸水后BMSC仍然存在着因体积稳定性和微细观结构变化导致的抗压强度下降，这将在很大程度上限制BMSC及其制品的广泛应用。本项目首先探明水化产物5Mg(OH)2·MgSO4·7H2O晶相（5·1·7相）稳定性与其结晶程度关系，通过原材料摩尔比、矿物掺合料和不同pH值化学外加剂调控，建立BMSC耐水性与其水化产物组成和结晶程度关系，增加水化产物5·1·7相稳定性，实现BMSC微细观结构优化。依据磷酸镁水泥反应原理，采用KH2PO4或NH4H2PO4溶液浸渍处理转化水化产物剩余MgO，增加BMSC浸水后体积稳定性及孔隙填充率。最终，基于微细观结构优化和剩余MgO转化实现BMSC耐水性提高，扩大BMSC及其制品应用的广泛性，为建筑可持续发展提供一种性能优异的镁质胶凝材料。

The mechanical strength and water resistance of basic magnesium sulfate cement (BMSC) modified by chemical additives are significantly improved, which is a green cementitious material with great development potential and good application prospect. However, the compressive strength of BMSC still decreases due to volume stability and micro- and meso structures changes after immersion in water, which will limit the wide application of BMSC and its products to a great extent. In this project, the relationship between the stability of hydration product 5Mg(OH)2·MgSO4·7H2O phase (5·1·7 phase) and its crystallinity is first investigated. The relationship between the water resistance of BMSC and the composition and crystallinity of its hydration products is established by adjusting the molar ratio of raw materials, mineral admixtures and different pH chemical additives, increase the hydration product 5·1·7 phase stability, thus achieving the micro- and meso structures optimization of BMSC. According to the reaction principle of magnesium phosphate cement, KH2PO4 or NH4H2PO4 solution is used for impregnation treatment to transform the residual MgO of hydration products and increase the volume stability and pore filling rate of BMSC after immersion in water. Finally, based on the micro- and meso structures optimization and residual MgO conversion, the water resistance of BMSC can be improved, and the application of BMSC and its products can be expanded, providing a magnesia-based cementitious material with excellent performance for the sustainable development of buildings.