磷、氟对水热法高强α半水磷石膏的制备及水化硬化性能的影响

Phosphogypsum utilization effectively has been a major problem related to sustainable development of phosphorus chemical industry and environmental protection. Aiming at the existing problems of phosphogypsum based building materials, such as lower added value, lacking of fundamental research on impurities influence on preparation of high-strength hemihydrate gypsum, effects of phosphorus and fluoride impurities on the preparation process, hydration and hardening properties of high- strength alpha hemihydrate gypsum by hydrothermal methods will be researched in this project. The structure- decomposition method of phase composition-crystal structure-product properties will be adopted. The dynamic changes and coupling effects of different kinds of phosphorus and fluoride in high-strength alpha hemihydrate gypsum crystal formations, crystal habits, crystal structure regulations, also in the processes of hydration and hardening are to be deeply explored. And then the inherent quantitative relations of the key influence factors, the hydration kinetics and the hardening properties will be analyzed in detail. Next effect laws and the action mechanisms of phosphorus, fluorine kinds and contents on crystal structures-properties of high strength alpha hemihydrate gypsum will be discussed. And the "integration" collaborative regulation mechanisms to comprehensively guarantee the quality of products with more key features will be finally determined. The project findings may provide necessary theoretical basis and technical supports for the research and applying of phosphogypsum based high–strength alpha hemihydrate gypsum products, further promote the efficient utilization of phosphogypsum and the developments of high-end gypsum building materials.

磷石膏的高效资源化利用已经成为关系磷化工行业可持续发展和环境保护的重大问题。本项目针对磷石膏建材资源化利用中存在的产品附加值低，磷、氟杂质对高附加值高强石膏的制备影响严重而相关基础研究缺乏的问题，分类研究磷、氟对水热法高强α半水磷石膏的制备过程及水化硬化性能的影响，采用“相变产物组成—晶体结构—产品性能”的结构化分解方法，探究不同种类的氟、磷在高强α半水磷石膏的晶体形成、晶体习性、晶型调控、水化硬化过程中的动态变化及耦合作用，分析关键影响因子与高强石膏胶凝材料的水化动力学、水化硬化性能的内在量化关联，揭示磷、氟的种类和含量对高强α半水磷石膏的晶体结构、水化硬化性能的影响规律和作用机理，确定综合保证产品多关键质量特性的“一体化”协同控制机制，为高强α半水磷石膏产制品的研发和应用提供必要的理论基础和技术支撑，从而促进磷石膏的高效资源化利用和高端石膏建材的发展。

磷、氟杂质是制约高强α半水磷石膏制备及应用的主要原因之一，本项目对磷、氟影响下高强α半水磷石膏的制备过程及水化硬化性能进行了全面、系统的研究，采用的制备方法分别为高压水热法和常压水热法。着重研究了磷、氟的种类和含量对高强α半水石膏晶体生长、结晶习性、晶形调控以及水化硬化性能的影响规律和作用机理。结果表明：1）常压水热环境下，可溶磷降低了体系的pH值，有利于α-HH相的形成，但同时也增大了a-HH相的晶体长度，削弱了媒晶剂的作用效果；高压水热条件下，可溶磷的种类和含量对α-HH晶习和强度产生复杂的影响；2）常压状态下可溶氟对α-HH晶体直径稍有增长，对强度提高效果有限，而在高压状态下可溶氟则主要通过吸附方式大幅增大α-HH的晶体直径，缩短其长径比并显著提高强度；3）不溶性磷、氟对α-HH晶习的影响主要是增大晶体直径，对提高产品强度有利；加入微溶性氟后出现共晶或孪晶现象，降低产品强度；当多种形式的磷、氟共存时，它们的耦合作用使得单种杂质的作用得到削弱； 4）可溶性磷、氟对高强石膏的凝结、强度性能均有不同程度的影响，而微溶性和不溶性磷、氟的影响较小；颗粒形态和粒度直接影响了α半水石膏的水化硬化性能和水化产物的微观结构。开发了针对不同水热环境和原料性质的高效媒晶剂，并明确了基于磷石膏原料性质和制备工艺的磷、氟杂质控制指标与处理措施。研究成果对促进高强石膏的制备技术和磷石膏高附加值应用具有重要的指导意义。