On shrinkage and structure changes of pure and blended Portland concretes |
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| Authors: | Yao Zhang Catherine A Davy Gregory Tricot Cyrille Albert‐Mercier Natacha Henry Pieter Bertier Frédéric Cazaux Denis Damidot Xavier Bourbon |
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| Affiliation: | 1. Key Laboratory of Energy Engineering Safety and Disaster Mechanics (Ministry of Education), College of Architecture & Environment, Sichuan University, Chengdu, China;2. CNRS, Arts et Métiers Paris Tech, Centrale Lille, Univ. Lille, FRE 3723 ‐ LML ‐ Laboratoire de Mécanique de Lille, Lille, France;3. L2MGC EA4114 Cergy‐Pontoise University, Cergy‐Pontoise, France;4. LASIR, UMR CNRS 8516, Université de Lille 1, Villeneuve d'Ascq Cedex, France;5. LMCPA, Université de Valenciennes, Maubeuge, France;6. UCCS, UMR CNRS 8181, Université de Lille 1, Villeneuve d'Ascq Cedex, France;7. RWTH Aachen University, Institute for Clay & Interface Mineralogy, Aachen, Germany;8. UMET, UMR CNRS 8207, Université de Lille 1, Villeneuve d'Ascq, France;9. EM Douai, Centre de Recherches, Douai, France;10. Andra, Chatenay‐Malabry, France |
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| Abstract: | This research investigates the long‐term shrinkage and Relative Mass Loss (RML) of mature Portland concretes (pure CEMI and blended CEMV/A), at temperatures of 20°C and 80°C. When placed at 80°C and at relative humidities (RH) below 50‐60%, concrete shrinkage increases with very slow stabilization kinetics by several hundreds of μm/m, while RML remains of about 0.2%. The origins of this continued shrinkage, simultaneously with limited RML, are investigated through the changes in (i) the pore structure of the concretes (by Mercury Intrusion Porosimetry and nitrogen adsorption) and in (ii) their solid phases (by TGA/DTA, FTIR spectroscopy coupled to DVS, quantitative X‐Ray Diffraction by Rietveld analysis, and 29Si and 27Al MAS NMR). While the pore structure coarsens during continued shrinkage, several phase transformations occur, namely ettringite decomposition and changes in the silicate chain length of the C–A–S–H. While these structural changes are documented, their relationship with shrinkage/RML and to the pore structure is novel. |
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| Keywords: | temperature drying shrinkage structure changes XRD solid state NMR |
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