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Cement / Strontium / Sorption / Sequential desorption Summary. We studied the sorption behavior of Sr onto calcium-silicate-hydrates (C-S-H), calcium-aluminate-hydrates ettringite (AFt), monosulphate (AFm), and hydrogarnet (C 3AH6) by applying a sequential desorption method. The results showed that:Ϫ The distribution coefficients (K d ) of Sr sorption onto C-S-H increased with decreasing Ca/Si ratios of C-S-H. This K d change is explained with the zeta potentials of C-S-H at various Ca/Si ratios and with the change of surface functional group,Ϫ Sr is sorbed on C-S-H through plural sorption forms. The observation that some Sr is desorbed by EDTA and nitric acid suggests that a replacement of Ca with Sr takes place in the C-S-H structure, andϪ Sr is structurally incorporated into AFt, AFm, and C 3 AH 6 .

Cement / Caesium / Sodium / Sorption / XRD / 29 Si NMRSummary. 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.

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We have studied the influence of interaction between CaO-Si02-H20 (C-S-H) gel and ettringite (AFt) on their dissolution regarding the initial chemical feature of degraded cement pore water. In this work, firstly dissolution experiments were performed in C-S-H gel at Ca/Si=l.0, 1.2 and 1.47 coexisting with AFt of which amount was 5% of mol corresponding to each C-S-H gel. Secondly, assuming the congruent dissolution of AFt, dissolution of the same system was calculated by combining with the dissolution model of C-S-H gel at l