Simulation of calcium carbonate nucleation processes in confined C-S-H nanopores with different calcium-silicon ratios

• Published in: Construction & building materials 2024-08, Vol.438, p.137157, Article 137157
• Main Authors: Yu, Jiao, Wang, Kerui, Yang, Peixuan, Li, Mengmeng, Dong, Biqin, Jin, Zuquan, Hong, Shuxian, Ma, Hongyan
• Format: Article
• Language: English
• Subjects: Calcium carbonate; Calcium silicate hydrate; Cluster process; Confined nanopores; Molecular dynamics simulation
• ISSN: 0950-0618; 1879-0526
• DOI: 10.1016/j.conbuildmat.2024.137157

Carbonation curing technology plays an important role in carbon cycling and improving the properties of cement-based materials, while the nucleation and growth mechanism of calcium carbonate (CaCO3) is still unclear. Based on molecular dynamics simulation, the formation process and nucleation mechanism of CaCO3 in confined C-S-H nanopores with different calcium-silicon ratios were studied. The results show that the clustering behavior of CaCO3 in C-S-H nanopores filled with saturated CaCO3 solution can be divided into three phases, rapid agglomeration stage, slow cluster stage, and stable cluster stage. The aggregation is mainly dependent on ionic bonding for nucleation growth and is consistent with the prenucleation mechanism. The Ca/Si ratio of C-S-H has a direct influence on the clustering of CaCO3. The anchoring mechanism of CaCO3 clusters is determined by ionic bonds and hydrogen bonds, and large clusters are preferentially adsorbed at the C-S-H interface through ionic bonds. The Ca/Si ratio of 1.5 can provide more nucleation sites by ionic bonds and hydrogen bonds for the formation of CaCO3, which is more conducive to the growth of clusters. And the calcium source from C-S-H in cluster bodies can be as high as 33 %. This study helps to understand the early formation process of CaCO3 in cement-based materials and lays a theoretical foundation for the development of carbonization curing technology. [Display omitted] •Cluster processes in nanoscale C-S-H channels.•Capture the calcium-silicon ratio effect of C-S-H.•The discovery of the nucleation mechanism.