In situ interactions between Opalinus Clay and Low Alkali Concrete

Publication date: Available online 18 January 2017 Source:Physics and Chemistry of the Earth, Parts A/B/C Author(s): Catherine Lerouge, Stéphane Gaboreau, Sylvain Grangeon, Francis Claret, Fabienne Warmont, Andreas Jenni, Veerle Cloet, Urs Mäder A five-year-old interface between a Low Alkali Concrete (LAC) formulation (CEM III/B containing 66% slag and 10% nano-silica) and Opalinus Clay (OPA) from a field experiment at Mont Terri Underground Rock Laboratory in Switzerland (Jenni et al., 2014) has been studied to decipher the textural, mineralogical and chemical changes that occurred between the two reacting materials. Reactivity between LAC concrete and OPA is found to be limited to a ∼1mm thick highly porous (ca. 75% porosity) white crust developed on the concrete side. Quantitative mineralogical mapping of the white crust using an electron microprobe and infrared spectroscopy on the cement matrix provides evidence of a Mg-rich phase accounting for approximatively 25 weight % of the matrix associated with 11 weight % of calcite, calcium silicate hydrate (C-S-H) and other cement phases. EDX analyses and electron diffraction combined with transmission electron microscopy of the Mg-rich phase provide evidence for a tri-octahedral 2:1 phyllosilicate with mean composition: (Ca0.5±0.2) (Mg2.0±0.4, Fe0.2±0.1, Al0.5±03, □0.3±0.3) (Al0.9±0.2, Si3.1±0.2) O10 (OH)2, where □ represents vacancies in the octahedral site Apart from this reactive contact, textural...
Source: Physics and Chemistry of the Earth, Parts ABC - Category: Science Source Type: research