高温养护条件下现代水泥基材料早期微结构演变及调控机理研究

The high temperature curing conditions often encountered in the conservation of the large volume of concrete and precast concrete production process. Compared with normal temperature curing, high temperature curing causes a significant change in the internal microstructure of cementitious materials, which leads to decline of the physical and mechanical properties and durability of concrete. However, due to the complexity component of modern cementitious materials, there are still many doubts about the cementitious materials hydration mechanism. In this project, the newly designed high temperature ultrasonic instrument and improved non-electrode resistivity measuring instrument are used to in-situ continuously tracking the hydration process of modern cementitious materials. Besides, the Nanoindentation and atomic force microscopy, X-ray computed tomography, X-ray diffraction, Environmental scanning electron microscope are used to investigate the hydration prodcuts, the microstructural evolution and pore structure change of the modern cementitious materials. The influences of the mineral admixtures, chemical admixtures and water-cement ratio on the hydration mechanism of modern cementitious materials under high temperature curing are revealed. Based on experimental data, the hydration kinetics model and microstructure formation mechanism model account for the effect of curing temperature and mineral admixtures are established. Finally, the numerical simulation is used for 3D reconstruction of the early hydration process, which can intuitive show the evolution of the microstructure formation process. The project can improve the hydration dynamics theory of inorganic cementitious materials.

高温条件是大体积砼和砼制品生产过程中常常遇到的养护情况，与常温相比高温养护会使水泥基材料内部微结构发生显著变化，并导致其物理力学性能及耐久性能下降，但由于现代水泥基材料组分复杂，目前对其高温养护下早期水化机理仍存众多疑惑。本项目利用自行设计研发的新型高温超声波测量仪和改进的无电极电阻率测量仪，原位、持续地追踪观测现代水泥基材料早期的水化历程全貌；并采用纳米压痕、原子力显微镜、X射线计算机断层扫描、XRD、ESEM等先进现代微观测试技术，对现代水泥基材料水化产物、微结构演变、孔结构变化过程进行研究，揭示高温养护下矿物掺合料、化学外加剂、水灰比等因素对水化机理的影响规律；基于实验数据，建立与温度、矿物掺合料相关的现代水泥基材料水化动力学模型及微结构形成机理模型；最后，利用数值模拟方法对早期水化进行3D重构，直观展现微结构的演变过程。本项目将为完善和发展无机胶凝材料的水化动力学理论奠定科学基础。

现代水泥基材料组分复杂，目前对其高温养护下早期水化机理仍存众多疑惑。本项目自行设计研发的新型高温超声波测量仪和改进的无电极电阻率测量仪，原位、持续地追踪观测现代水泥基材料早期的水化历程，发现养护温度的提高显著促进了水化速率，粉煤灰对水化进程有一定的延缓作用，但是硅灰表现为明显的促进作用，矿渣作用不明显；采用XRD、ESEM等先进现代微观测试技术，对现代水泥基材料水化产物、微结构演变、孔结构变化过程进行研究，发现粉煤灰和硅灰有火山灰效应与填充效应，可以显著改善现代水泥基材料的微观结构与性能。最后，基于水化动力学理论，采用 CEMHYD3D水化模型，基于真实胶凝材料粒径分布、矿物组成等信息，模拟凝材料水化过程，获取产物、各种理参数以及不同度下微结构信息，真实再现了现代水泥基材料早期水化、硬化微结构形成过程，实现材料微观组织动态演化的精确仿真。本项目将为完善和发展无机胶凝材料的水化动力学理论奠定科学基础。