Control of drying shrinkage in magnesium silicate hydrate (m-s-h) gel mortars |
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| Affiliation: | 1. Faculty of Infrastructure Engineering, Dalian University of Technology, Dalian 116000, China;2. Department of Materials, Centre for Advanced Ceramics, Imperial College London, London, SW7 2AZ, UK;3. Department of Civil and Environmental Engineering, Imperial College London, London, SW7 2AZ, UK;1. Andra — Scientific Division, 1-7 Rue Jean Monnet, Parc de la Croix Blanche, 92298 Chatenay-Malabry Cedex, France;2. BRGM, 3 Avenue Claude Guillemin, 45060 Orléans Cedex 2, France;3. CNRS, CEMHTI, UPR 3079, 45071 Orléans, France;4. Empa, Laboratory for Concrete & Construction Chemistry, Überlandstrasse 129, 8600 Dübendorf, Switzerland;5. Université de Poitiers-CNRS, UMR7285 IC2MP, Equipe HydrASA, Poitiers 86022, France;1. HeidelbergCement Technology Center GmbH, 69181 Leimen, Germany;2. Empa, Laboratory for Concrete & Construction Chemistry, 8600 Duebendorf, Switzerland;3. Department of Chemistry and Interdisciplinary Nanoscience Center (iNANO), Aarhus University, DK-8000 Aarhus C, Denmark;1. University of Bern, Institute of Geological Sciences, RWI Group, 3012 Bern, Switzerland;2. Empa, Laboratory for Concrete & Construction Chemistry, 8600 Dübendorf, Switzerland;3. CEA, DEN, DE2D, SEAD, F-30207 Bagnols-sur-Cèze cedex, France;4. IRSN, Institute of Radiation Protection and Nuclear Safety, PSE/SEDRE/LETIS, BP 17, 92262 Fontenay aux Roses, France;5. UTINAM UMR 6213 CNRS, Université Bourgogne-Franche-Comté, 25030 Besançon, France |
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| Abstract: | Magnesium silicate hydrate (M-S-H) gel can be formed by the reaction of MgO with amorphous silica in the presence of sodium hexametaphosphate (Na-HMP). Typical pastes contain 40% MgO and 60% SF and have a w/c ratio of 0.5, but these exhibit shrinkage cracking on drying. The shrinkage characteristics of M-S-H mortar samples containing different additions of sand have been studied using dilatometry. The drying shrinkage was found to decrease with increasing sand addition and to increase with increased water content. Mortars with 60 wt.% sand addition and a w/c ratio of 0.5 had a drying shrinkage of 0.16% and did not show shrinkage cracking. A simple geometrical model based on particle packing is presented that explains the observed changes in drying shrinkage. Based on the geometrical model, the shrinkage of M-S-H mortar system can be reduced to zero when the volume fraction of sand in the mortar is about 0.77. |
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