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Understanding the deformation mechanism and mechanical characteristics of cementitious mineral analogues from first principles and reactive force field molecular dynamics†
Physical Chemistry Chemical Physics ( IF 3.3 ) Pub Date : 2018-04-19 00:00:00 , DOI: 10.1039/c7cp08640g
Jinyang Jiang 1, 2, 3 , Yiru Yan 1, 2, 3 , Dongshuai Hou 3, 4, 5 , Jiao Yu 3, 4, 5
Affiliation  

In this paper, first principles and reactive force field molecular dynamics were utilized to study the mechanical properties of tobermorite 9 Å, tobermorite 11 Å and jennite. These are essential minerals in cement chemistry. The mechanical properties calculated by the first-principle method match well with previous experimental results, pointing to the introduction of vdW dispersion-type forces as able to improve the precision. The calculated elastic constants of the three minerals confirm anisotropic mechanical behavior of the layered structures. The crystals jennite and tobermorite 9 demonstrate stronger mechanical behavior in the ab plane than the interlayer direction due to the presence of stable covalent “dreierketten” silicate chains. For tobermorite 11 Å, the Q3 silicate tetrahedrons bridging the neighboring calcium silicate sheets heal the weak interlayer structure and enhance the c-direction stiffness and cohesive strength. Furthermore, analysis of uniaxial tension by reactive force MD elucidated the chemical and mechanical responses of the atomic structures in loading resistance. The stress–strain relation of the layered mineral tensioned along b direction, showing the “strain hardening” region, where stress continues to increase past the yield stage. The strain hardening and ductility enhancement for the minerals is largely due to the ability of the silicate chains to first de-polymerize into short chains or separate tetrahedrons before the broken Q species re-polymerize to form branched networks and ring structures which are able to resist loading. For all three minerals, protons transfer to oxygen and water, resulting in the formation of Si–OH and Ca–OH groups during the strain hardening stage as Si–O–Si or Si–O–Ca bonds start to break and the calcium atoms and silicate morphology is rearranged. Hydrolysis therefore accelerates structural damage and contributes to weakening of mechanical properties in the interlayer direction. Increased tensile stress level in the tobermorite 11 Å can contribute to a greater extent of water damage.

中文翻译:

通过第一原理和反作用力场分子动力学了解胶结矿物类似物的变形机理和力学特性

在本文中,第一性原理和反作用力场分子动力学被用来研究9硅钙石,11硅钙石和菱镁矿的力学性能。这些是水泥化学中必不可少的矿物质。通过第一原理方法计算的机械性能与先前的实验结果非常吻合,指出引入vdW分散型力可以提高精度。计算出的三种矿物的弹性常数证实了层状结构的各向异性力学行为。由于存在稳定的共价“ dreierketten”硅酸盐链,所以晶铁矿和钙铁矿9在ab平面中表现出比层间方向更强的机械行为。对于雪铁矿11Å,Q 3桥接相邻硅酸钙片的硅酸盐四面体可修复薄弱的中间层结构并增强c方向的刚度和内聚强度。此外,通过反作用力MD对单轴张力的分析阐明了在负载阻力方面原子结构的化学和机械响应。沿b方向张紧的层状矿物的应力-应变关系显示出“应变硬化”区域,该区域应力在屈服阶段之后继续增加。矿物的应变硬化和延展性增强很大程度上归因于硅酸盐链在断裂的Q物种重新聚合以形成能够抵抗的支链网络和环结构之前,先解聚为短链或分离的四面体的能力。加载中。对于所有三种矿物质,质子都会转移到氧气和水中,导致在应变硬化阶段形成Si–OH和Ca–OH基团,因为Si–O–Si或Si–O–Ca键开始断裂,钙原子和硅酸盐形态重新排列。因此,水解会加速结构破坏,并导致层间方向的机械性能减弱。辉钼矿11Å中拉应力水平的增加可能会导致更大程度的水损坏。
更新日期:2018-04-19
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