Source data of cement hydration inhibition by silane coupling agents elucidated from atomistic simulations and hydration experiments

Silane coupling agents are widely recognized to retard early hydration when incorporated into fresh cement paste, yet the atomic-level mechanisms underlying their effects on clinker dissolution, such as the adsorption of silane monomer onto reactive surface sites and the modification of ion detachment pathways, remain largely unexplored. Here we show dissolution pathways of tricalcium silicate (Ca₃SiO₅) under 3-aminopropyl triethoxysilane impact using <i>ab initio</i> metadynamics, with subsequent experimental validation of the retardation effects in silane-treated pastes. The shielding effect of silane induces a shift in the free energy changes of stepwise calcium dissolution from negative to positive and alters the most stable coordination state of calcium during dissolution, resulting in the transition of calcium dissolution from spontaneous to non-spontaneous. Specifically, hydrolyzed silane monomer dissociatively adsorbs onto Ca₃SiO₅ surface by forming ionic Ca-O bonds, thereby occupying reactive sites and introducing steric hindrance. This, in turn, impedes coordination between calcium ions and water molecules. Experimental results further corroborate these interactions, as evidenced by reduced calcium concentrations in silane-treated pastes, which in turn slowed hydration process. These findings offer nanoscopic insights into the role of SCAs in cement hydration and provide a foundation for future research into the complex interactions within organic/cement systems.

硅烷偶联剂（silane coupling agents）已被广泛证实，当掺入新鲜水泥浆体中时可延缓其早期水化，但硅烷偶联剂对熟料溶解的影响背后的原子级机制，例如硅烷单体在活性表面位点的吸附以及离子脱离路径的调控，迄今仍未得到充分探究。本研究通过从头算元动力学（ab initio metadynamics）模拟了3-氨基丙基三乙氧基硅烷（3-aminopropyl triethoxysilane）作用下硅酸三钙（tricalcium silicate, Ca₃SiO₅）的溶解路径，并通过实验验证了硅烷改性水泥浆体的缓凝效果。硅烷的屏蔽效应使得分步钙溶解过程的自由能变化由负值转为正值，并改变了溶解过程中钙最稳定的配位状态，最终使钙溶解从自发过程转变为非自发过程。具体而言，水解后的硅烷单体通过形成离子型Ca-O键解离吸附在硅酸三钙表面，从而占据活性位点并引入空间位阻，进而阻碍了钙离子与水分子之间的配位作用。实验结果进一步佐证了上述相互作用：经硅烷处理的浆体中钙离子浓度降低，这也使得水化进程得以延缓。本研究结果为理解硅烷偶联剂在水泥水化中的作用提供了纳米尺度的视角，并为未来研究有机-水泥复合体系内的复杂相互作用奠定了基础。