Structure alteration of C-S-H (calcium silicate hydrated phases) caused by sorption of caesium

Summary The sorption behavior of Cs onto C-S-H (calcium silicate hydrated phases) was investigated by evaluating the effect of sorption on the C-S-H structure. The C-S-H have a tobermorite-type layer structure. Each layer consists of central calcium and oxygen atoms sandwiched by silicate tetrahedral chains. Additional calcium and water are located in interlayer zones. The XRD spectra showed that the tobermorite-type layer degraded and that the sorption of Cs made the fragments of layer intergrowths much smaller. The fragmentation of the tobermorite-type layer was observed for C-S-H in contact with CsCl solution or with CsOH solution, but not for the C-S-H in contact with Na solution. Furthermore, 29 Si NMR spectroscopy revealed that the sorption of Cs onto C-S-H induced cleavages of silicate chains in C-S-H. It was also suggested that the OH − ion contributed to breaking the silicate chains.