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Preferred orientation of calcium aluminosilicate hydrate induced by confined compression
Cement and Concrete Research ( IF 11.4 ) Pub Date : 2018-11-01 , DOI: 10.1016/j.cemconres.2018.09.002
Guoqing Geng , Roman Nikolayevich Vasin , Jiaqi Li , Mohammad Javad Abdolhosseini Qomi , Jinyuan Yan , Hans-Rudolf Wenk , Paulo J.M. Monteiro

Abstract The existing macroscale models of the calcium (alumino)silicate hydrate (C-(A-)S-H), the main binder of concrete, assume that the nanocrystallites maintain random orientation under any loading conditions. However, using synchrotron-radiation-based XRD, we report the development of preferred orientation of nanocrystalline C-A-S-H, from random at ambient pressure to strongly oriented under uniaxial compression with lateral confinement. The c-axes of the nanocrystals tend to align with the primary load. This preferred orientation is preserved after removing of external loading. The texture, quantified using a standard Gaussian fiber orientation distribution function (ODF), was used to calculate the averaged bulk elastic tensor of oriented C-(A-)S-H. It changes from isotropic (without texture) to transversely isotropic (with texture). Our results provide direct evidence of the reorientation of nanocrystalline C-(A-)S-H as a mesoscale mechanism to the irreversible deformation of cement-based material. The implications of these results for modeling the mechanical property of C-(A-)S-H at the macroscale are discussed.

中文翻译:

受限压缩引起的硅铝酸钙水合物的优选取向

摘要 现有的混凝土主要粘结剂(铝)硅酸钙水合物 (C-(A-)SH) 的宏观模型假设纳米微晶在任何载荷条件下都保持随机取向。然而,使用基于同步辐射的 XRD,我们报告了纳米晶 CASH 择优取向的发展,从环境压力下的随机到单轴压缩下具有横向限制的强取向。纳米晶体的 c 轴倾向于与主要负载对齐。在移除外部负载后,该首选方向得以保留。使用标准高斯纤维取向分布函数 (ODF) 量化的纹理用于计算取向 C-(A-)SH 的平均体积弹性张量。它从各向同性(无纹理)变为横向各向同性(有纹理)。我们的研究结果直接证明了纳米晶 C-(A-)SH 的重新定向是水泥基材料不可逆变形的中尺度机制。讨论了这些结果对宏观尺度 C-(A-)SH 力学性能建模的影响。
更新日期:2018-11-01
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