Zhao Cheng, Zhou Wei, Zhou Qi, Zhang Yao, Liu Han, Sant Gaurav, Liu Xinghong, Guo Lijie, Bauchy Mathieu
State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China.
Physics of AmoRphous and Inorganic Solids Laboratory (PARISlab), Department of Civil and Environmental Engineering, University of California, Los Angeles, California 90095, USA.
J Chem Phys. 2020 Jul 7;153(1):014501. doi: 10.1063/5.0010476.
Concrete gains its strength from the precipitation of a calcium-alumino-silicate-hydrate (C-A-S-H) colloidal gel, which acts as its binding phase. However, despite concrete's ubiquity in the building environment, the atomic-scale mechanism of C-A-S-H precipitation is still unclear. Here, we use reactive molecular dynamics simulations to model the early-age precipitation of a C-A-S-H gel. We find that, upon gelation, silicate and aluminate precursors condensate and polymerize to form an aluminosilicate gel network. Notably, we demonstrate that the gelation reaction is driven by the existence of a mismatch of atomic-level internal stress between Si and Al polytopes, which are initially experiencing some local tension and compression, respectively. The polymerization of Si and Al polytopes enables the release of these competitive stresses.
混凝土通过钙铝硅酸盐水合物（C-A-S-H）胶体凝胶的沉淀获得强度，该胶体凝胶作为其粘结相。然而，尽管混凝土在建筑环境中无处不在，C-A-S-H沉淀的原子尺度机制仍不清楚。在此，我们使用反应分子动力学模拟来模拟C-A-S-H凝胶的早期沉淀。我们发现，在凝胶化时，硅酸盐和铝酸盐前驱体凝聚并聚合形成硅铝酸盐凝胶网络。值得注意的是，我们证明凝胶化反应是由硅和铝多面体之间原子级内应力不匹配的存在驱动的，硅和铝多面体最初分别经历一些局部拉伸和压缩。硅和铝多面体的聚合使得这些竞争应力得以释放。
