Chemical alteration of calcium silicate hydrate (C–S–H) in sodium chloride solution

Modelling of Chemical Alteration of Cement Materials in Radioactive Waste Repository Environment

“…It is noted that a lower diffusion coefficient was provided for FAC than for OPC even though the porosity of FAC (29%) was higher than that of OPC (12%). Similar observations were given by Sugiyama et al (2008) and Sugiyama (2007, 2008): they observed that the effective diffusion coefficients of uranium , organic carbon , caesium, strontium and iodine in the FAC matrix were more than an order of magnitude lower than those in the OPC matrix, though the porosity of FAC was higher than that of OPC. The reason for the lower diffusion coefficients for FAC is still unclear, but it should be interpreted using the smaller pore size distribution in the FAC matrix .…”

“…The chemistry of the CaO-SiO 2 -H 2 O (C-S-H) system is a key parameter since it is suggested to be responsible for the high-pH condition in cements and is important in discussing the high-pH chemical condition in the long-term assessment of a repository environment Atkinson, 1985). The author therefore has been developing a series of predictive calculation models based on a discussion of the incongruent dissolution/precipitation of the C-S-H system (Sugiyama & Fujita, 2006;Sugiyama, 2008).…”

Alteration of nanocrystalline calcium silicate hydrate (C-S-H) at pH 9.2 and room temperature: a combined mineralogical and chemical study

“…The preferential release of Ca observed during the first step is certainly due to the dissolution of impurities, and then to the release of interlayer Ca because layer Ca is strongly bound and is certainly not released in early stages of alteration. XRD provides clues to the preferential release of interlayer Ca, through the decrease in the layerto-layer distance which certainly results from the replacement of Ca by Na from the input solution (Bach et al, 2013;Sugiyama, 2008). In particular, Bach et al (2013) observed, on a C-S-H sample with a C/S ratio of 0.83, a decrease in the layer-tolayer distance with increasing Na concentration in the solution: layer-to-layer distance was 13.98 Å after equilibration in a Na-free solution as compared to a position of the (001) reflection of 13.50 Å in sample C-S-H_0.9i.…”

X-ray spectromicroscopic study of interactions between NaCl and calcium silicate hydrates

“…The interaction between C-S-H and NaCl aqueous solution is therefore of great importance and several works on this topic have been reported (Hill et al, 2006;Kalinichev and Kirkpatrick, 2002;Sugiyama, 2008;Sugiyama andFujita, 2004, 2006;Viallis et al (1999). Viallis et al (1999) studied the structure of silicate tetrahedra and adsorbed sodium ions with solid-state nuclear magnetic resonance (NMR) spectroscopy.…”

“…Hill et al (2006) investigated the behaviour of C-S-H in saline solution and the effect of Ca/Si ratio, temperature and cationic type on this behaviour. Sugiyama (2008) also emphasised the importance of cationic interaction with C-S-H and successfully described the exchange reaction of sodium with calcium in C-S-H using a thermodynamic model. However, most of the studies to date have not considered the significance of anionic interaction with C-S-H when cement-based materials come into contact with NaCl solutions.…”