Pressure solution of quartz aggregates under low effective stress (0.42–0.61 MPa) at 25–45 °C |
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| Institution: | 1. Department of Chemistry, University of Helsinki, P.O. Box 55, 00014, Finland;2. AMPHOS 21 CONSULTING S.L, Passeig de Garcia i Fària, 49-51 08019 Barcelona, Spain;3. Posiva Oy, Finland;4. Nagra (National Cooperative for the Disposal of Radioactive Waste), Wettingen, Switzerland;1. ENEA, National Agency for New Technologies, Energy and Sustainable Economic Development, UTTRI S.S. 106 Ionica, km 419+500, 75026 Matera, Italy;2. UTRINN/STD, Via Anguillarese 301, 00123 Roma, Italy;3. University of Calabria, Department of Environmental and Chemical Engineering, Via P. Bucci Cubo 44a, I-87036 Arcavacata di Rende, CS, Italy;1. Division of Earth and Environmental Sciences, Korea Basic Science Institute (KBSI), Cheongju 28119, Republic of Korea;2. Department of Earth System Sciences, Yonsei University, Seoul 03722, Republic of Korea;3. Korea Institute of Nuclear Safety (KINS), Daejeon 34142, Republic of Korea;1. Department of Geosciences and Geography, University of Helsinki, P.O. Box 64, 00014 Helsinki, Finland;2. Posiva Oy, Olkiluoto, 27160 Eurajoki, Finland;3. Department of Geosciences, Swedish Museum of Natural History, P.O. Box 50 007, SE-10405 Stockholm, Sweden;1. Department of Landscape Geochemistry and Soil Geography, Faculty of Geography, GSP-1, Leninskie gory, Moscow, 119991, Russian Federation;2. Institute of Geography, Erkhuu street, Sukhbaatar district, UB-14192, Ulaanbaatar, Mongolia |
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| Abstract: | Dissolution rates of pressure solution (PS) for quartz aggregates in 0.002 M NaHCO3 solution were experimentally determined under low effective stress conditions of 0.42–0.61 MPa, and low temperatures of 25–45 °C. At temperatures of 25 °C, 35 °C, and 45 °C, the resultant silicon dissolution rates are 4.2 ± 1.2 × 10?15, 6.0 ± 1.0 × 10?15 and 7.8 ± 1.9 × 10?15 mol/cm2/s, respectively. Ratios between these dissolution rates and those of quartz sand at zero effective stress are 4.1 ± 1.2 at 25 °C, 3.0 ± 0.5 at 35 °C, and 2.4 ± 0.6 at 45 °C. As the uniaxial pressure was increased, the dissolution rate of PS also increased, though gradually decreased when the effective stress was kept constant. After the removal of stress, the dissolution rate was observed to increase once again. The activation energy of our PS experiments was determined to be approximately 24 kJ/mol, lower than the amount required for quartz sand dissolution to commence at zero effective stress. Our results clearly show that, even at such low temperature and effective stress, Si released into solution as a result of PS can be detected. This implies that experimental compaction of quartz aggregates can be measured even under such condition. |
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