Development of a ReaxFF Reactive Force Field for Ettringite and Study of its Mechanical Failure Modes from Reactive Dynamics Simulations
Development of a ReaxFF Reactive Force Field for Ettringite and Study of its Mechanical Failure Modes from Reactive Dynamics Simulations
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钙矾石 ReaxFF 反作用力场的开发及其通过反应动力学模拟研究其机械失效模式
DOI：
10.1021/jp210135j
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发表时间：
2012-04-19
影响因子：
2.9
通讯作者：
Sun, Huai
中科院分区：
文献类型：
--
作者：
Liu, Lianchi;Jaramillo-Botero, Andres;Sun, Huai
钙矾石是硅酸盐水泥水化过程中形成的一种六铝酸钙水合三硫酸氢盐矿物。它的存在对控制水泥浆体中高活性铝酸盐相的凝结速率起着重要作用，也与固化硬化水泥的严重开裂有关。为了了解它是如何形成的，以及它的性质如何影响硬化水泥和混凝土的性质，我们开发了基于第一性原理的Ca/Al/H/O/S的ReaxFF反作用力场。在这里，我们报告了ReaxFF力场的发展及其验证和应用，使用反应分子动力学（RMD）模拟来表征和理解钙矾石在原子尺度上的弹性、塑性和破坏响应。通过对比RMD模拟和实验得到的钙矾石晶体模型的晶格参数、两两分布函数和弹性常数，验证了ReaxFF力场的有效性。预测结果与已发表的实验数据非常吻合。为了表征钙矾石的原子破坏模式，我们进行了应力-应变模拟，发现钙- o键是钙矾石中硫酸钙和三铝酸钙（C3A）柱在单轴压缩和拉伸过程中破坏的原因，而压缩过程中氢键的重新形成导致塑性应变增加超过材料的应力-应变比例极限。这些结果为理解这种矿物在水泥和混凝土降解中的机制作用提供了重要的见解，并且本工作中开发的ReaxFF潜力可作为进一步研究水泥和混凝土水化动力学的基础工具。
Ettringite is a hexacalcium aluminate trisulfate hydrate mineral that forms during Portland cement hydration. Its presence plays an important role in controlling the setting rate of the highly reactive aluminate phases in cement paste and has also been associated with severe cracking in cured hardened cement. To understand how it forms and how its properties influence those of hardened cement and concrete, we have developed a first-principles-based ReaxFF reactive force field for Ca/Al/H/O/S. Here, we report on the development of this ReaxFF force field and on its validation and application using reactive molecular dynamics (RMD) simulations to characterize and understand the elastic, plastic, and failure response of ettringite at the atomic scale. The ReaxFF force field was validated by comparing the lattice parameters, pairwise distribution functions, and elastic constants of an ettringite crystal model obtained from RMD simulations with those from experiments. The predicted results are in close agreement with published experimental data. To characterize the atomistic failure modes of ettringite, we performed stress-strain simulations to find that Ca-O bonds are responsible for failure of the calcium sulfate and tricalcium aluminate (C3A) column in ettringite during uniaxial compression and tension and that hydrogen bond re-formation during compression induces an increase in plastic strain beyond the material's stress-strain proportionality limit. These results provide essential insight into understanding the mechanistic role of this mineral in cement and concrete degradation, and the ReaxFF potential developed in this work serves as a fundamental tool to further study the kinetics of hydration in cement and concrete.