科研之友
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摘要
Hydration of minerals, playing fundamental role in many technological applications, involves multi-stage chemical reactions, morphology changes and compositional variations. For the first time, the hydration mechanism for the tricalcium silicate was investigated by the combination of C3S hydration experimentally and polymerization of silicate-monomers via molecular dynamics simulation. Tricalcium silicate was self-synthesized and utilized to hydrate with water at the water/solid ratio of 50. Samples hydrated from one day to one year were obtained and characterized by XRD, IR, SEM, NMR and TEM techniques. Based on SEM observation, the morphology of hydrated C3S transformed from small localized to foil-like wrinkled clusters with fibrillar-like wrinkles distributed randomly. Wrinkled product of C-S-H possessed poor-crystallined or amorphous feature based on XRD and TEM analysis. Such was also evidenced by the fact that no layered crystal phase was observed in simulated calcium silicate gel clusters. Besides, the simulated pair distribution function of C-S-H gel demonstrating the structure feature of short range order and long range disorder, also confirmed glassy structural nature for the C-S-H gel. Furthermore, based on NMR and SEM results C/S ratio changed to 1.2 and the mean silicate chain length in C-S-H was obtained at around 4 after hydration for one year with Q1 and Q2 species representing linear silicate chain structure present dominantly. The molecular dynamics helped illuminate the hydration mechanism that the morphology of C-S-H gel was closely related with C/S ratio. At C/S ratio of 1, solid branched 3-dimmensional cluster was segregated from the solution while ellipsoid colloid particle with the size of 4 nm x 4 nm x 8 nm was formed at C/S ratio of 1.75. It was also found that calcium ions prevented thepolymerization reaction of silicate monomers and silicate chains were shortened significantly at high Cal Si ratio, amplifying the predominate percentage of Q1 species in the C-S-H gel.
