Uniaxial tensile deformation and fracture process of structures forming by unsaturated intercalation of amine molecule into C-S-H gel
Uniaxial tensile deformation and fracture process of structures forming by unsaturated intercalation of amine molecule into C-S-H gel
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胺分子不饱和插层C-S-H凝胶结构单轴拉伸变形及断裂过程
DOI：
10.1007/s00894-021-04998-5
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发表时间：
2022
影响因子：
2.2
通讯作者：
Zhiyong Wang
中科院分区：
文献类型：
--
作者：
Dawei Sun;Yan Zheng;Jianhua Yan;Yali Wang;Jianfeng Wang;Ziming Wang;Zherui Chen;Yufeng Cai;Suping Cui;Mingzhang Lan;Zhiyong Wang
水泥基材料在工程中的应用，需要了解其特性以及服役中C-S-H凝胶的后续变形和断裂过程。本研究成功地将四乙基戊二胺（TEPA）、聚丙烯酰胺（PAM）和三乙醇胺（TEA）三种胺类分子以不饱和状态插入C-S-H凝胶中。系统地分析了C-S-H凝胶和相应的胺分子/ C-S-H凝胶的结构和性能。研究发现，胺类分子在C-S-H凝胶中的不饱和插层对纳米复合材料的几何形状和密度起着关键作用。随后，利用径向分布函数（RDF）、时间相关函数（TCF）和均方位移（MSD）表征了纳米复合材料的结构和动态信息，证明了胺分子与Ca-Si层之间存在相互作用，并通过胺分子不饱和插入到C-S-H凝胶的层间区域加速了水的扩散。最后，通过分子动力学模拟给出了C-S-H凝胶和胺分子/ C-S-H凝胶在单轴拉伸载荷作用下的变形和断裂过程。结果表明，纳米复合材料的切线模量表现为应变软化性质，具有粘弹性特性。C-S-H凝胶的断裂以Ca-O键和氢键断裂为主。TEPA/ C-S-H凝胶或TEA/ C-S-H凝胶的弱相互作用导致拉伸强度下降。尽管PAM分子中的双键极性氧原子与C-S-H凝胶中的Ca原子形成了强相互作用，但在其他层间区域的局部应力集中控制了变形和断裂过程。
The application of cement-based materials in engineering requires the understanding of their characteristics and subsequent deformation and fracture process of C–S–H gel in service. In this work, three types of amine molecules including tetraethylenepentamine (TEPA), polyacrylamide (PAM), and triethanolamine (TEA) were intercalated into C–S–H gel in an unsaturated status successfully. Systematical analysis was performed on the structures and properties for both C–S–H gel and corresponding amine molecules/C–S–H gel. It was found that the unsaturated intercalation of amine molecules into C–S–H gel plays a key role in the geometry and therein density of nanocomposites. Subsequently, radial distribution function (RDF), time-correlated function (TCF), and mean square displacement (MSD) were applied to characterize the structure and dynamic information of the as-generated nanocomposites, demonstrating the occurrence of interaction between amine molecules with Ca–Si layer and acceleration of water diffusion by unsaturated intercalation of amine molecules into the interlayer region in C–S–H gel. Finally, the deformation and fracture process of C–S–H gel and amine molecules/C–S–H gel under uniaxial tensile loads were given by molecular dynamics simulation. It was indicated that the tangent modulus of nanocomposites demonstrates a strain-softening nature, indicating a visco-elastic behavior. The breakage of Ca–O bonds and hydrogen bonds dominates the fracture of C–S–H gel. Weak interaction for TEPA/C–S–H gel or TEA/C–S–H gel leads to a decreased tensile strength. Local stress concentration in other interlayer region governs the deformation and fracture process in spite of the formation of strong interaction between double bonded polar oxygen atoms in PAM molecules and Ca atoms in C–S–H gel.