Groundwater-rock interactions cement

Cement-equilibrated water derived from the repository will react with the surrounding rock and form an alkaline-disturbed zone (ADZ) around the repository. The main reactions that are expected to occur within the ADZ are dissolution of primary silicates, and precipitation of hydrated calcium silicates (CSH phases) and possibly zeolites (Rochelle et al. 1992). As such water-rock interaction proceeds, the pH of the repository-derived water will be buffered toward lower values and will eventually reach the nearneutral values typical of unperturbed far-field groundwaters. It is likely that the hydrogeological and radionuclide retardation properties of the ADZ will be different from those of the unperturbed geosphere. The NSARP therefore includes work to evaluate the size of the ADZ and the extent to which its properties will be perturbed. A summary of the ADZ sorption programme is presented below. 

Sedimentary rock A rock that formed from the natural cementing of sediments during burial, compaction, and interactions with groundwater (clastic sedimentary rocks) or that resulted from the burial and diagenesis of materials excreted from organisms or salts that precipitated from surface water. 

Coombs, P., Gardner, S. J., Rochelle, C. A. West, J. M. 1998. Natural analogue for geochemistry and microbiology of cement porewaters and cement porewater host rock/near-field interactions. In Linklater, C. (ed.) A natural analogue of cement-buffered groundwaters and their interaction with a repository host rock II. Nirex Science Report, S-98-003. Nirex, Didcot, UK. 

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