Expansion of clay minerals in expansive soil, such as montmorillonite (MMT), is critical to a broad class of problems in science and engineering. Cement is one of the most widely used materials in the treatment of expansive soil. However, at present, the expansion mechanism of the soil treated by cement has not been thoroughly investigated at the nanoscale level. In this paper, four types of cement-stabilized MMT (Na-MMT, K-MMT, Ca-MMT, and Mg-MMT) molecular models with different interlayer cations and surface charges are established and validated by experimental data. The maximum adsorption energies of the four different cement-stabilized MMT systems are then investigated through molecular simulations, and the optimum water ratios are proposed for the four cement-stabilized MMT systems to achieve proper volume stability. The numerical simulations also show that the volume change of cement-stabilized MMT depends not only on the water-absorbing capacity but also on the CSH–MMT interface energy as well as the competitive absorption of CSH and MMT. For different types of expansive soil, Mg²⁺ or K⁺ modification may be used to improve the efficiency of the expansion control.

中文翻译：

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通过分子动力学模拟揭示不同层间阳离子水泥稳定膨胀土的膨胀机理

在诸如蒙脱石（MMT）之类的膨胀土壤中膨胀黏土矿物对科学和工程学中的一系列广泛问题至关重要。水泥是膨胀土处理中使用最广泛的材料之一。然而，目前，在纳米水平上，尚未对水泥处理过的土壤的膨胀机理进行彻底研究。本文建立了具有不同层间阳离子和表面电荷的四种水泥稳定MMT（Na-MMT，K-MMT，Ca-MMT和Mg-MMT）分子模型，并通过实验数据进行了验证。然后通过分子模拟研究了四个不同的水泥稳定的MMT系统的最大吸附能，并提出了四个水泥稳定的MMT系统的最佳水比，以实现适当的体积稳定性。数值模拟还表明，水泥稳定的MMT的体积变化不仅取决于吸水能力，还取决于CSH-MMT界面能以及CSH和MMT的竞争吸收。对于不同类型的膨胀土，Mg可以使用²⁺或K ⁺修改来提高扩展控制的效率。