基于分子动力学的水化硅铝酸钙微结构和性能研究

Recent research in fields of material science and archaeology shows that the calcium aluminate silicate hydrate (C-A-S-H) is the essential component to improve the durability of concrete. However, the fundamental properties of C-A-S-H have not been investigated comprehensively. The aim of our project is to build the molecular model of C-A-S-H and study the mechanical, dynamic and transport properties. The C-A-S-H samples are first synthesized. The X-ray diffraction method, FI-IR and SEM are utilized to characterize the microstructure of C-A-S-H samples, including the chemical composition, morphology and crystal structure, which can be taken as the input and verification parameters for the molecular simulation. Meanwhile, based on the quantum mechanical calculation, the reactive force field is derived to accurately describe the interactions between Ca, Si, Al, O and H atoms. Furthermore, reactive force field molecular dynamics and Monte Carlo method are combined to study the water adsorption, polymerization of Si-Al chains and decomposition of structural water, and finally construct a realistic model for C-A-S-H. In addition, the model is further applied to study the influence of water content and Ca/Al ratio on the structure and properties of C-A-S-H, and the water and ions transport in the nanopores. The project is the fundamental study of the concrete material, which can provide theoretical basis for the design of cement with mineral admixtures and for improving the durability of concrete material.

最新材料学与考古学研究表明，水化硅铝酸钙 (CASH) 是提高混凝土耐久性的关键组分，但其基础研究尚不完善。本项目拟建立CASH 的分子动力学模型，在此基础上研究其动力学、力学及传输特性。项目将合成CASH样品并综合利用X射线衍射法、傅里叶红外测试和扫描电镜等测试技术表征其微观结构，得到其化学成分、形貌特征及晶体结构，并以此作为分子模拟的输入参数与验证依据。同时，利用量子力学计算结果推导出准确描述钙、硅、铝、氧、氢多元素体系化学反应力场。利用该反应力场，结合分子动力学和蒙特卡洛方法，计算吸水过程、硅铝相聚合反应和结构水水解反应，并最终建立较为真实的分子动力学模型。在此基础上阐明CASH结构和力学性能随含水量和钙铝比的演化规律，并且解决离子和水在纳米孔道中的传输问题。项目拟研究的内容属混凝土结构材料基础研究，研究成果将为矿物掺合料水泥的设计提供理论依据，为混凝土耐久性的大幅提升提供理论基础。

水化硅铝酸钙是水泥与富含铝相矿物掺和料的主要水化产物，其微观分子结构决定着混凝土材料的力学性能与耐久性能。本项目通过反应场分子动力学与微观实验相结合的方法，推导出描述水泥体系的化学反应力场，构建了切合实际的水化硅铝酸钙的分子模型，成功的预测了材料在纳米尺度的结构，动力学与力学特性。分子动力学模型的构建，揭示了铝相在水化产物层间与硅链的多重配位结构，科学的阐述了铝相在水泥水化过程的硅链聚合反应与水分羟基化所起到的关键桥接作用。基于反应场分子动力学模型重点研究了水化产物的微观分子结构随钙硅比，水分含量等化学组分演变规律，解码了微观分子结构与性能的关联机制，提出了基于微结构理论的水泥基材料优化与调控准则，为高性能混凝土材料的设计提供了理论基础。并且研究了水分和离子在水化硅铝酸钙的凝胶孔道中的迁移与吸附，探明了含铝相矿物对于侵蚀离子的固化机理，揭示了硫酸盐等侵蚀性离子对于胶凝材料的劣化机制，探明了高聚合度的铝相对于水化硅铝酸钙骨架的稳固作用，提升了抗硫酸盐侵蚀的作用，为混凝土材料的耐久性设计提供了科学的指导。