Geochemical constraints on the stability of zeolites and C–S–H in the high pH reaction of bentonite

Authigenic Clay Minerals from Interface Reactions of Concrete-Clay Engineered Barriers: A New Perspective on Mg-Clays Formation in Alkaline Environments

“…It is calculated that at pH 11 for the equilibrium montmorillonite-C-A-S-H at the interface it is needed the dissolution of <10 wt % of the initial montmorillonite content in order to satisfy equilibrium conditions. This limit imposed by C-S-H/montmorillonite equilibrium was shown by Fernández et al [48] in their thermochemical interpretation of Ca(OH) 2 -montmorillonite reactions. In fact, this limit can have favourable consequences as it enables the precipitation or retention of amphoteric metal ions that can be solubilized at higher pHs as it is the case of Al and radionuclides as U(VI), Tc(IV), Np(V) [49].…”

Rock alteration in alkaline cement waters over 15 years and its relevance to the geological disposal of nuclear waste

“…Modelling has also been used to predict the chemical and physical evolution within the CDZ (e.g. Savage et al, 1992;Savage and Rochelle, 1993;Braney et al, 1993;Bateman et al, 1999;Pfingsten et al, 2006;Soler and Mäder, 2007;Fernandez et al, 2010;Alexander et al, 1992). These studies generally support the experimental findings that silicate mineral dissolution is followed by secondary solid phase (e.g.…”

ThermoChimie database developments in the framework of cement/clay interactions

“…Indeed, a survey of the literature highlights difficulties in collecting enough mineralogical and chemical information on a single case (from experiment or field observations), in order to process the verification directly. For example, an assessment of a chabazite stability field by the Fernández et al (2010) experiments failed since only muscovite was found to be stable in the final solutions reported at 25°C. Thus, through verification we instead correct the substantial inconsistencies that would arise from the critical selection, such as for the case of gismondine, described earlier.…”

“…A typical problem arises when mineralogical determinations are based on XRD alone, as it does not provide precise enough information for chemical composition and degree of hydration. Errors are also possible when trying to derive thermodynamic properties from experiments performed in supersaturated conditions (Fernández et al, 2010).…”