The interfacial characteristics of geopolymer binder to aggregate composites are poorly understood, especially at molecular level. Herein, molecular models are developed to study, for the first time, the geopolymer-aggregate interface. Chemically, various forms of interfacial bonding are characterized, including Al-O-Si bonding through condensation reactions, NaO and H-bonding. An atomic-level interfacial transition zone (ITZ) is identified, attributed to the concentration of –OH groups. Increasing the Si/Al ratio of geopolymer is found to decrease the ITZ density, but have limited effect on the ITZ width. A heterogeneous diffusion characteristic occurs in geopolymer, due to the weak interfacial interaction. Mechanically, lowering the Si/Al ratio promotes the interfacial strength due to the stronger interfacial interaction and higher cross-linking degree in geopolymer. Under loading the interfacial fracture undergoes three stages: crack propagation, chain bridging (including aluminosilicate and ionic bridging) and breakage. The above atomic-level findings may facilitate a better design of geopolymer concrete in engineering.

人们对地质聚合物粘合剂与骨料复合材料的界面特性知之甚少，尤其是在分子水平上。在此，首次开发了分子模型来研究地质聚合物-骨料界面。在化学上，表征了各种形式的界面键合，包括通过缩合反应的 Al-O-Si 键合、NaO 和 H 键合。确定了原子级界面过渡区 (ITZ)，归因于 -OH 基团的浓度。发现增加地质聚合物的 Si/Al 比会降低 ITZ 密度，但对 ITZ 宽度的影响有限。由于弱的界面相互作用，地质聚合物中出现异质扩散特性。在机械上，由于地质聚合物中更强的界面相互作用和更高的交联度，降低 Si/Al 比可提高界面强度。在载荷作用下，界面断裂经历三个阶段：裂纹扩展、链桥（包括铝硅酸盐和离子桥）和断裂。上述原子级发现可能有助于在工程中更好地设计地质聚合物混凝土。