In recycling and reusing construction waste, carbonation of recycled concrete fine (RCF) has been successfully applied to produce value-added products, such as silica nanoparticles, via the breaking of calcium silicate hydrate (C-S-H) structure and condensation of silicate chains. However, the intricacies of carbonation of RCF with varying calcium to silicon (C/S) ratios and their implications on the size of generated silica nanoparticles remain unknown. In this work, we developed an optimized carbonation method at high water to solid ratio to fabricate silica nanoparticles from C-S-H with different C/S ratios. The particle size of silica nanoparticles was found to gradually decrease with the increased C/S ratio of C-S-H. Since as C/S ratio increased, silicate in Q3 state shifted to Q1 state and the silicate chain became shorter, shifting from long-range, disordered to short-range, ordered. As the disordered self-seeding growth of long silicate chains derived from C-S-H continued, the Si-O-Si network of silica nanoparticles became chaotic, leaving more unreacted Si-OH on its surface. On the contrary, the short silicate chains displayed higher possibility of condensation, making nanoparticles with a smaller diameter.

中文翻译：

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高水固比下 C-S-H 衍生的二氧化硅纳米颗粒的 Ca/Si 依赖性尺寸


在建筑垃圾的回收和再利用方面，再生混凝土细粒 （RCF） 的碳化已成功应用于通过破坏硅酸钙水合物 （CSH） 结构和硅酸盐链的冷凝来生产增值产品，例如二氧化硅纳米颗粒。然而，具有不同钙硅 （C/S） 比率的 RCF 碳化的复杂性及其对生成的二氧化硅纳米颗粒尺寸的影响仍然未知。在这项工作中，我们开发了一种高水固比的优化碳化方法，以不同 C/S 比的 C-S-H 制备具有不同 C/S 比的二氧化硅纳米颗粒。发现二氧化硅纳米颗粒的粒径随着 C-S-H 的 C/S 比的增加而逐渐减小。由于随着 C/S 比值的增加，Q3 状态的硅酸盐转变为 Q1 状态，硅酸盐链变短，由长程、无序变为短程、有序。随着源自 C-S-H 的长硅酸盐链无序自种子生长的继续，二氧化硅纳米颗粒的 Si-O-Si 网络变得混乱，在其表面留下更多未反应的 Si-OH。相反，短硅酸盐链显示出更高的缩合可能性，使纳米颗粒的直径更小。