Structure and Intrinsic Mechanical Properties of Nanocrystalline Calcium Silicate Hydrate
Structure and Intrinsic Mechanical Properties of Nanocrystalline Calcium Silicate Hydrate
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DOI：
10.1021/acssuschemeng.0c03230
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发表时间：
2020-08-24
影响因子：
8.4
通讯作者：
Monteiro, Paulo J. M.
中科院分区：
文献类型：
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作者：
Li, Jiaqi;Zhang, Wenxin;Monteiro, Paulo J. M.
纳米水化硅酸钙（C-S-H）是许多低CO2水泥的粘结相。了解其结构-力学性能关系对于设计可持续混凝土至关重要。首次通过共沉淀法制备了Ca/Si比为0.8-1.5的C-S-Hs的类似基面间距（仅0.17 A变化）。用X射线吸收光谱测定了C-S-H的纳米结构，用高压X射线衍射测定了不同Ca/Si比下C-S-H的本征纳米力学性能。首次消除了基底间距对纳米力学性能的影响。在相似的基底间距下，ab平面不可压缩性保持独立于Ca/Si和硅酸盐链长，而c轴不可压缩性由层间密度（即，层间Ca含量）。C-S-H的体积模量由层间密度决定-在可比的基底间距下，更多的层间Ca产生更高的体积模量。结果表明，在较高的Ca/Si比下，共沉淀C-S-Hs具有较高的力学性能。研究结果对设计绿色水泥/混凝土具有重要意义，可为多尺度模拟提供性能输入，为验证计算方法/参数提供参考。
Nanocrystalline calcium silicate hydrate (C-S-H) is the binding phase of many low-CO2 cements. Understanding its structure-mechanical properties relationship is critical in designing sustainable concrete. For the first time, a similar basal spacing (only 0.17 A variation) of C-S-Hs at Ca/Si ratios of 0.8-1.5 is prepared via coprecipitation. The C-S-H nanostructure is determined using X-ray absorption spectroscopy, and the intrinsic nanomechanical properties of C-S-H at various Ca/Si are measured using highpressure X-ray diffraction. For the first time, the influence of basal spacing on the nanomechanical properties is eliminated. At similar basal spacing, the ab-planar incompressibility remains independent of Ca/Si and silicate chain length, while the c-axis incompressibility is governed by the interlayer density (i.e., interlayer Ca content). The bulk modulus of C-S-H is governed by the interlayer density-more interlayer Ca yields higher bulk modulus at comparable basal spacings. Our results show that coprecipitated C-S-Hs at higher Ca/Si have higher mechanical properties. The results have implications in designing green cement/concrete using bottom-up approaches by providing property inputs for multiscale simulation and references for validating computational methods/parameters.