In situ interactions between Opalinus Clay and Low Alkali Concrete

摘要: Abstract A five-year-old interface between a Low Alkali Concrete (LAC) formulation (CEM III/B containing 66% slag and 10% nano-silica) Opalinus Clay (OPA) from field experiment at Mont Terri Underground Rock Laboratory in Switzerland (Jenni et al., 2014) has been studied to decipher the textural, mineralogical chemical changes that occurred two reacting materials. Reactivity LAC concrete OPA is found be limited ∼1 mm thick highly porous (ca. 75% porosity) white crust developed on side. Quantitative mapping of using an electron microprobe infrared spectroscopy cement matrix provides evidence Mg-rich phase accounting for approximatively 25 wt % associated with 11 wt calcite, calcium silicate hydrate (C-S-H) other phases. EDX analyses diffraction combined transmission microscopy provide tri-octahedral 2:1 phyllosilicate 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 octahedral site. Apart this reactive contact, modifications contact are limited. mineralogy remains largely unmodified. X-ray micro-fluorescence EPMA major elements side also Mg-enriched 300–400 μm layer. The cation exchange capacity (CEC) values measured range 153 175 meq kg−1 dry OPA, close reference value 170 ± 10 (Pearson 2003). Changing occupancies mainly marked by increased Ca, Mg K, decreased Na. Leaching tests performed deionized water different solid ratios strongly suggest Cl SO4 have either conservative behaviour or constrained solubility precipitated sulfate phase. concentrations 2 cm undisturbed pore waters (SO4: 4.5 ± 1.5 mmol kg−1 OPA; Cl: 7.5 ± 2.1 mmol kg−1of OPA), increase towards concrete. ratio increases interface, suggesting increasing anion not related porosity variations but rather concentration gradient precipitation near interface.