钙矾石形貌的可控性及调控机理研究

The formation and stability of ettringite has important effect on properties of hardened calcium silicate cement especially sulphoaluminate cement or other special cement. Nowadays, the environment in which ettringite forms becomes more complicated as different inorganic and organic admixtures are added in cement system, as a result the morphology of ettringite become more diverse, this change in morphology has important effect on the expansion and volume stability of concrete, the research in controllability of ettringite morphology becomes quite necessary. The project will focus on controllability of ettringite morphology and the regulation mechanism, physical and chemical properties of ettringite with different morphology will be investigated. Substitution, adsorption and bonding characteristics between inorganic ions, ionic groups, organic polar groups and ettringite will be studied. Synergic effect of inorganic salts and polycarboxylate on morphology of ettringite in liquid environment will be studied. Effect of ettringite morphology controllability on actual performance of special cement such as sulphoaluminate cement will be investigated. Regulation mechanism of ettringite morphology in complex liquid environment will be revealed, and a method for controllbility of ettringite morphology will be formed so as to explore the method in real special cement system for practical application. This project is important for enriching the basic theory of ettringite morphology, optimizing the matching of ettringite morphology and properties of special cement, enhancing the performance in hardened special cement.

钙矾石的形成与稳定对硅酸盐水泥特别是硫铝酸盐水泥等特种水泥的硬化体性能具有重要影响。近年来，随着各种无机与有机外加剂的广泛应用，钙矾石的形貌变得越来越多样，由于钙矾石形貌对混凝土的膨胀性、体积稳定性等有重要影响，因此关于钙矾石形貌控制的研究显得愈发重要。课题拟围绕钙矾石的形貌控制与调控机理问题，研究不同形貌钙矾石的物理化学性能；研究无机离子、离子团、有机极性基团等与钙矾石间的取代、吸附、键合特征；研究液相环境下无机盐与聚羧酸减水剂协同作用对钙矾石形貌的影响；研究钙矾石的形貌调控在硫铝酸盐水泥等特种水泥内的实际效能；揭示复杂液相环境下钙矾石形貌的调控机理，形成一套钙矾石生成形貌的控制方法，探索钙矾石的形貌调控在特种水泥体系内的实际应用。研究成果对丰富关于钙矾石形貌的基础理论，实现钙矾石形貌与特种水泥硬化体性能的优化匹配，以及提升特种水泥硬化体性能有重要意义。

钙矾石是硫铝酸盐水泥水化的主要产物，决定着硫铝酸盐水泥的性能，且在硅酸盐水泥混凝土中其影响也非常重要。钙矾石的形成条件决定了其形貌，其形成时间影响着水泥和混凝土的性能。钙矾石形成和形貌的研究，对水泥混凝土性能的改善具有重要的意义。.采用铝酸三钙和二水石膏、硫铝酸钙和二水石膏、氢氧化钙和硫酸铝三组原材料，在溶液中合成了纯的钙矾石。采用电子扫描电镜（SEM）、X射线衍射（XRD）、热分析（TG-DSC）、红外光谱（IR）等测试技术，研究了合成时间、原材料、合成温度、pH值、不同掺量的硼酸、碳酸锂、聚羧酸减水剂等对钙矾石形成和形貌的影响。.1. 不同原材料合成的钙矾石形貌显著不同且长宽比差异显著，以C3A和二水石膏为原材料合成的钙矾石尺寸远小于其他两组原材料合成的钙矾石，长宽比约为其他两组长宽比的1/10；在100℃合成温度下，钙矾石不能稳定存在，在较短的时间后就会转化为单硫型水化硫铝酸钙；随着液相pH值的增加，钙矾石的长宽比逐渐减小，且钙矾石形貌由长杆状向细小的针状转变。溶液中钙矾石的形成机理为：既可直接生成钙矾石，又可先形成单硫型水化硫铝酸钙，而后单硫型水化硫铝酸钙和SO42–、Ca2+反应形成钙矾石。.2. 硼酸能够抑制钙矾石的生长，随着硼酸掺量的增加，钙矾石的长宽比逐渐减小，尺寸变短，当硼酸掺量提高到10%、20%时，出现了较多的扁柱状的钙矾石；碳酸锂通过吸附在钙矾石晶体的侧面，抑制钙矾石晶体宽度的生长，碳酸锂可以加快钙矾石的形成速度；聚羧酸减水剂对钙矾石晶体宽度上的生长起到抑制作用，使得钙矾石晶体变长变细，长宽比明显增加，但对钙矾石成核起到促进作用。.3. 提出了钙矾石形貌调控的方案。通过掺加碳酸锂和聚羧酸减水剂均可获得长杆状钙矾石；调节pH值为12.5以上时，可以获得细针状钙矾石；掺加硼酸可以获得短柱状钙矾石；硼酸与聚羧酸减水剂复合掺加，可以获得又短又细的钙矾石。