The Calcium Silicate Hydrate (C-S-H) nucleation is a crucial step during cement hydration and determines to a great extent the rheology, microstructure, and properties of the cement paste. Recent evidence indicates that the C-S-H nucleation involves at least two steps, yet the underlying atomic scale mechanism, the nature of the primary particles and their stability, or how they merge/aggregate to form larger structures is unknown. In this work, we use atomistic simulation methods, specifically DFT, evolutionary algorithms (EA), and Molecular Dynamics (MD), to investigate the structure and formation of C-S-H primary particles (PPs) from the ions in solution, and then discuss a possible formation pathway for the C-S-H nucleation. Our simulations indicate that even for small sizes the most stable clusters encode C-S-H structural motifs, and we identified a C₄S₄H₂ cluster candidate to be the C-S-H basic building block. We suggest a formation path in which small clusters formed by silicate dimers merge into large elongated aggregates. Upon dehydration, the C-S-H basic building blocks can be formed within the aggregates, and eventually crystallize.

硅酸钙水合物（CSH）成核是水泥水化过程中的关键步骤，在很大程度上决定了水泥浆体的流变性、微观结构和性能。最近的证据表明，CSH 成核至少涉及两个步骤，但潜在的原子尺度机制、初级粒子的性质及其稳定性，或者它们如何合并/聚集形成更大的结构尚不清楚。在这项工作中，我们使用原子模拟方法，特别是 DFT、进化算法 (EA) 和分子动力学 (MD)，研究溶液中离子的 CSH 初级粒子 (PP) 的结构和形成，然后讨论可能的CSH成核的形成途径。我们的模拟表明，即使对于小尺寸，最稳定的簇也编码 CSH 结构基序，并且我们确定了 C ₄ S ₄ H ₂候选簇作为 CSH 基本构建块。我们提出了一种形成路径，其中由硅酸盐二聚体形成的小簇合并成大的细长聚集体。脱水后，CSH 基本结构单元可在聚集体中形成，并最终结晶。