炎热环境下海水拌和水泥基材料微结构形成与演变机理研究

使用海水拌制水泥基材料，不仅可以解决南海岛礁国防基础设施混凝土拌和用水匮乏的问题，而且可以大力推动海砂资源的利用。然而在南部海域常年炎热和海水中氯离子、硫酸根离子以及镁离子等的叠加作用下，改变了传统淡水拌和水泥基材料的微结构形成与演变过程。本项目以海水拌和水泥基材料为对象，采用高温超声波测量仪和改进后的无电极电阻率测量仪等设备，原位、持续追踪观测不同养护温度下其早期水化过程，揭示温度和海水中离子叠加作用对水泥基材料水化历程的影响规律；采用现代微观测试技术，探明炎热环境下海水拌和水泥基材料水化产物种类、C-S-H凝胶的微结构演变、Al取代Si程度以及Al相产物迁移与转变的演变机理；基于水泥基材料水化产物及微结构形成过程，建立不同养护温度下海水拌和水泥基材料水化模型。研究成果为高温严酷环境下使用海水拌和水泥基材料奠定理论基础，同时为提升海水侵蚀条件下混凝土的耐久性设计水平提供依据。

Mixing cement-based materials with seawater directly can not only promote the utilization of sea sand resources, but also solve the problem of water shortage for concrete mixing of national defense infrastructure in island reefs of the South China Sea. However, the formation and evolution of the microstructure of traditional cement-based materials mixed with freshwater have been changed under the superposition of perennial heat in the southern sea area and chloride ion, sulfate ion and magnesium ion in seawater. This project takes cement-based materials mixed with seawater as the object, tracks and observes their early hydration process at different curing temperatures in situ and continuously using high-temperature ultrasonic measuring instrument and improved electrodeless resistivity measuring instrument, and reveals the influence law of superposition of temperature and ion in seawater on the hydration process of cement-based materials. Besides, modern micro-testing technologies are used to find out the types of hydration products under the coupling action of temperature and seawater, the microstructure evolution of C-S-H gel, the degree of substitution of Si by Al, and the evolution mechanism of migration and transformation of Al phase products. The hydration models of cement-based materials mixed with seawater at different curing temperatures are built based on the hydration products and microstructure formation process of cement-based materials. The research results can lay a theoretical foundation for mixing cement-based materials with seawater under high temperatures and harsh environments, and provide a basis for improving the concrete durability design under seawater erosion conditions.