Deconstructing water sorption isotherms in cement pastes by lattice density functional theory simulations
Deconstructing water sorption isotherms in cement pastes by lattice density functional theory simulations
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DOI：
10.1111/jace.17829
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发表时间：
2021-04
影响因子：
3.9
通讯作者：
Yao Zhang;Han Liu;Cheng Zhao;J. W. Ju;M. Bauchy
中科院分区：
文献类型：
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作者：
Yao Zhang;Han Liu;Cheng Zhao;J. W. Ju;M. Bauchy
水泥浆体中的水分含量影响其机械性能和耐久性。然而，水泥浆体复杂、多尺度的性质使得分离每个尺度对其宏观吸水等温线的贡献具有挑战性。特别是，硅酸钙水合物凝胶（水泥浆的粘合相）的贡献仍然只有部分了解。在这里，我们引入了描述硅酸钙水合物中水吸附的密度泛函理论晶格模型，该模型正确地再现了水泥浆体中的实验水吸附等温线。基于该模型，我们解构了每个孔隙尺度（层间距、凝胶孔和毛细孔）对总吸附等温线的贡献。我们发现，当相对湿度低于 80% 时，硅酸钙水合物凝胶占水泥浆体中吸附水分含量的 90% 以上。反过来，我们发现硅酸钙水合物颗粒内层间空间的贡献是由层间空间开放速率与相对湿度增加时水填充更大孔隙的倾向之间的竞争决定的。总的来说，我们的结果强调了硅酸钙水合物在控制水泥浆体吸附等温线方面发挥的关键作用。
The moisture content in cement pastes influences their mechanical properties and durability. However, the complex, multiscale nature of cement pastes makes it challenging to isolate the contributions of each scale to their macroscopic water sorption isotherms. In particular, the contribution of the calcium–silicate–hydrate gel (the binding phase of cement pastes) remains only partially understood. Here, we introduce a density functional theory lattice model describing water sorption in calcium–silicate–hydrate, which properly reproduces experimental water sorption isotherms in cement pastes. Based on this model, we deconstruct the contribution of each pore scale (interlayer spacing, gel pores, and capillary pores) to the total sorption isotherm. We show that, when the relative humidity is below 80%, the calcium–silicate–hydrate gel accounts for more than 90% of the moisture content adsorbed in cement pastes. In turn, we find that the contribution of the interlayer space within the calcium–silicate–hydrate grains is governed by the competition between the rate of interlayer space opening and the increasing propensity for water to fill larger pores upon increasing relative humidity. Overall, our results highlight the key role played by the calcium–silicate–hydrate in governing the sorption isotherms of cement pastes.