Characterization of contact properties in biocemented sand using 3D X-ray micro-tomography
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The mechanical efficiency of the biocementation process is directly related to the microstructural properties of the biocemented sand, such as the volume fraction of calcite, its distribution within the pore space (localized at the contact between grains, over the grain surfaces) and the contact properties: coordination number, contact surface area, contacts orientation and types of contact. In the present work, all these micromechanical properties are computed, for the first time, from 3D images obtained by X-ray tomography of intact biocemented sand samples. The evolution of all these properties with respect to the volume fraction of calcite is analyzed and compared between each other (from untreated sand to highly cemented sand). Whatever the volume fraction of calcite, it is shown that the precipitation of the calcite is localized at the contacts between grains. These results are confirmed by comparing our numerical results with analytical estimates assuming that the granular medium is made of periodic simple cubic arrangements of grains and by considering two extreme cases of precipitation: (1) The calcite is localized at the contact, and (2) the grains are covered by a uniform layer of calcite. In overall, the obtained results show that a small percentage of calcite is sufficient to get a large amount of cohesive contacts.
KeywordsBiocementation Contact orientation Contact surface area Coordination number MICP X-ray micro-tomography
This research is part of the BOREAL project founded under FUI 16 program and receives financial support from BPI, Metropole de Lyon and CD73. The authors acknowledge the technical support provided by Axelera Indura and all the BOREAL project partners for this research, and in particular the CNR company for funding the first author’s PhD thesis. 3SR laboratory is part of the LabEx Tec 21 (Investissements d’Avenir–Grant Agreement ANR11 269 LABX0030).
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