In situ interactions between Opalinus Clay and Low Alkali Concrete

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

“…On the other hand, the presence of hydrotalcite-type compositions and the secondary tendency to form saponitic compositions implies the existence of a sufficient high pH condition to allow the aluminium mobility and, hence, the dissolution of part of the montmorillonite mineral. The possibility of formation of saponitic minerals have been found also in low pH concrete matrices in contact with Opalinus Clay at the Mont Terri URL [14]. Our FTIR data showed similarities with this study and outline some bands indicative of Al-Si substitutions, which in one hand support the presence of saponite and also the dissolution of montmorillonite due to the above-mentioned mobility of aluminium soluble species.…”

“…Mg-silicates have been found at the clay-concrete (OPA) interface. In this case, the M-S-H phases are located in the concrete matrix and not in the clay side [8,14]. In addition to these processes, Al-Ca sulphates, chlorides and mono-hemi-carbonates [44] can precipitate in the concrete face due to the accommodation of Al (i.e., by montmorillonite dissolution) and soluble salts diffusion through the bentonite [11,45].…”

“…The formation of a Mg enriched zone within the concrete-clay interface, characterized by the formation of Mg-silicates hydrates (M-S-H), is known as Mg-perturbation. It has been recognized elsewhere when clay rocks or compacted bentonite are held in contact with solid cementitious materials [8,[10][11][12][13][14]. Usually, the source of Mg comes from the bentonite exchange complex or through the dissolution of Mg minerals in the concrete (i.e., brucite) or in the clay rocks (dolomite, serpentine, chlorite).…”

Alkali binding by magnesium silicate hydrates

“…Experiments of Brew and Glasser indicated that M–S–H could bind the alkali ions potassium and cesium. Additionally, M–S–H phases have an ill‐defined structure comparable to hydrated nano‐sized 2:1 and/or 1:1 phyllosilicates and M–S–H exhibits a negative surface charge as observed by acoustophoresis and cation exchange capacity (CEC) measurements . As in clays, the negative surface charge is caused by the presence of deprotonated silanol groups at the edges and/or in vacancies in the silicate layers of the M–S–H.…”

RTM for Waste Repositories

“…This is a long-term passive diffusion-reaction experiment between contrasting materials of relevance to engineered barrier systems/near-field for deep disposal of radioactive waste in claystone (Opalinus Clay). The sampled interfaces have been (and are still) extensively characterized from the mineralogical and petrophysical point of view (Jenni et al 2014(Jenni et al , 2017Dauzeres et al 2016;Lerouge et al 2017). The two other in situ interfaces were sampled in the Tournemire underground research laboratory.…”