考虑矿物各向异性的地聚物/集料界面静动态交互特征模拟

地聚物作为一种低碳环保、应用潜力广阔的无机结合料，其与不同表面构造集料的界面交互作用直接影响地聚物混凝土的力学性能和耐久性。充分考虑集料矿物晶向的各向异性，采用分子动力学模拟(Molecular Dynamics， MD)从原子分子层次的作用模式和强度分析，模拟了地聚物主要水化成分N-A-S-H、C-A-S-H和集料矿物化学成分SiO₂、CaCO₃不同晶面的静态界面相互作用，并采用单轴拉伸方法从纳米尺度下讨论了不同界面交互的动态力学行为。模拟结果表明：CaCO₃各晶面表现出比SiO₂更强的表面能和表面浸润性，并与C-A-S-H、N-A-S-H的界面相互作用势和拉伸应力更强，但CaCO₃晶面各向异性明显，性能稳定性不及SiO₂。地聚物与集料矿物的相互作用势主要由静电势提供，由于矿物界面静电作用及浸润特征，交互区水分子聚集，氢键作用明显，同时水分子与Ca²⁺、Na⁺进行配位形成水合离子，有助于离子在矿物表面迁移、沉淀与成核生长，增强界面空间位阻效应。在单轴拉伸模拟中，地聚物与集料矿物界面拉伸失效机制包括2个阶段：第1阶段(0 nm＜界面位移d＜0.15 nm)主要克服界面交互的静电作用，第2阶段(0.15 nm≤d≤0.3 nm)主要克服氢键作用。MD模拟有助于从分子尺度揭示地聚物与集料界面作用机制，为进一步研究地聚物混凝土材料优化、交互界面强化及损伤等提供了新方法和理论依据。

Static and Dynamic Interfacial Interactions of Geopolymer-aggregate Considering Anisotropic Mineral Surfaces: A Molecular Dynamics Study

Geopolymer, as a low-carbon environmental protection and valuable inorganic cementitious material, its interfacial interaction with aggregates with different surface structures directly affects the mechanical properties and durability of geopolymer concrete. In this study, considering the anisotropy of aggregate minerals surfaces, molecular dynamics (MD) simulation was used to investigate the interfacial interaction between geopolymer and aggregate. Simulating at the atomic and molecular level, the static interfacial interaction between N-A-S-H, C-A-S-H and SiO₂, CaCO₃ was simulated. Then the dynamic mechanical behavior of different interfacial interaction systems was carried out by direct tensile simulation. The simulation results show that the surface energy and wettability of CaCO₃ are stronger than that of SiO₂, and the interfacial interaction potential and tensile stress of CaCO₃ with C-A-S-H and N-A-S-H are stronger. However, the anisotropy of CaCO₃ crystal surface is significant, and its performances are more unstable than that of SiO₂. The interaction energy between geopolymer and aggregate minerals is mainly provided by electrostatic energy. And in the interaction zone, water molecules gathered and hydrogen bonding is obvious because of the electrostatic interaction and wettability of mineral surfaces. In addition, water molecules coordinate with Ca²⁺ and Na⁺ to form hydrated ions, which is conducive to ion migration, precipitation, nucleation, and growth on the mineral surface, and enhances the interfacial steric hindrance effect. In direct tension simulation, the failure mechanism of geopolymer-aggregate interface includes two stages. The first stage is caused by electrostatic interaction being overcome (0 nm＜d＜0.15 nm), and the second is caused by hydrogen bond fracture at the interface (0.15 nm≤d≤0.3 nm).