The Atomic-Level Structure of Cementitious Calcium Silicate Hydrate
The Atomic-Level Structure of Cementitious Calcium Silicate Hydrate
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DOI：
10.1021/acs.jpcc.7b02439
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发表时间：
2017-08-17
影响因子：
3.7
通讯作者：
Bowen, Paul
中科院分区：
文献类型：
--
作者：
Kumar, Abhishek;Walder, Brennan J.;Bowen, Paul
由于缺乏与硅酸钙水化相的原子级结构和生长相关的知识，调节混凝土整体物理性能的努力受到阻碍，硅酸钙水化相的体积约占水泥浆体体积的50%-60%。在这里，我们描述了第一次合成组成均匀的水化硅酸钙相，其钙硅比在1.0到2.0之间可调。合成的水化硅酸钙不含二次Ca(OH)(2)相，即使在钙硅比大于1.6的样品中也是如此，这在合成硅酸钙体系中是前所未有的。然后，我们利用动态核极化增强的H-1和Si-29核磁共振实验，结合原子模拟和密度泛函理论化学位移计算，求解了这些材料的原子级三维结构。我们发现，层间钙离子的桥联是单相胶凝硅酸钙水合物的决定性结构特征，导致了在高Ca：Si比下稳定结构的强烈氢键。
Efforts to tune the bulk physical properties of concrete are hindered by a lack of knowledge related to the atomic-level structure and growth of calcium silicate hydrate phases, which form about 50-60% by volume of cement paste. Here we describe the first synthesis of compositionally uniform calcium silicate hydrate phases with Ca:Si ratios tunable between 1.0 and 2.0. The calcium silicate hydrate synthesized here does not contain a secondary Ca(OH)(2) phase, even in samples with Ca:Si ratios above 1.6, which is unprecedented for synthetic calcium silicate hydrate systems. We then solve the atomic-level three-dimensional structure of these materials using dynamic nuclear polarization enhanced H-1 and Si-29 nuclear magnetic resonance experiments in combination with atomistic simulations and density functional theory chemical shift calculations. We discover that bridging interlayer calcium ions are the defining structural characteristic of single-phase cementitious calcium silicate hydrate, inducing the strong hydrogen bonding that is responsible for stabilizing the structure at high Ca:Si ratios.