2025 Volume 78 Issue 1 Pages 26-34
In this study, microstructure of Calcium Silicate Hydrate（C-S-H）agglomeration, so-called C-S-H gel, formed during cement hydration, and that of synthetic C-S-H was compared by 1H NMR T1-T2 correlation measurements. Based on T1-T2 correlation maps, C-S-H gel in hardened cement paste（HCP）showed all the relaxation components were on-diagonal at the same T1/T2 ratio, which is the measure of mobility of 1H. However, 1Hs in interlayer/gel-sized pores of synthetic C-S-H decayed at different T1/T2 ratios, similar to the result of layered clay minerals. From the viewpoint of 1H relaxation mechanisms in porous materials, experiments indicated microstructures of C-S-H gel in HCP and synthetic C-S-H are different. Synthetic C-S-H shares some similarities with layered clay minerals, indicating 1H in interlayer/gel-sized pores likely exhibits different mobility compared to those in bulk regions. On the other hand, C-S-H gel in HCP is more disordered and contains interlayer and gel between neighboring CaO layers. According to these assumptions, the length along the a-axis/b-axis of the pore having some fixed size in c-direction inside C-S-H gel may tend to be shorter than those in synthetic C-S-H. This can be the possible explanation for the difference in the microstructure of C-S-H gel in HCP and synthetic C-S-H.
