Durability of biocalcified porous materials exposed to solutions of varying aggressiveness: model-based measurements and short- and long-term issues

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4. Durability of biocalcified porous materials exposed to solutions of varying aggressiveness: model-based measurements and short- and long-term issues

Controlled biocalcification is an emerging way to increase the mechanical cohesion of granular materials through the formation of grain-bridging concretions in several industrial applications. However, this increase in cohesion can be lost through chemical dissolution and/or mechanical stress on the long term and can limit the applicability of such techniques. The long-term durability of biocalcified materials therefore needs to be assessed through studies of the factors and processes affecting their chemical and physical stability in realistic situations of chemical and physical stresses. This was the main goal of this study, in which the evolution of the cohesion of porous materials biocalcified by Sporosarcina pasteurii in a controlled manner in columns was measured during transfer tests of an aggressive solution optimised to accelerate the dissolution of calcite, consisting in particular of Tris-hydroxy-methyl-aminomethane (TRIS). In these tests, we monitored key chemical parameters such as electrical conductivity, pH and calcium concentration. Similar experimental and theoretical leaching tests conducted with pure water alone led to horizontal dissolution profiles, i.e. only dissolution of calcite at the point of entry into the column. Conversely, leaching with the optimised tris solution generated subvertical dissolution profiles. The pH of the solution of 6.6 and the moderate complexing strength of TRIS increase the solubility of calcite compared with pure water, which reduces the dissolution time and therefore allows calcite to be dissolved over a larger section and length of the column. Monitoring of the cohesion of the calcified material revealed a non-linear decrease in the mass of calcite exported. Thermodynamic modelling of our experiments made it possible to decipher the dissolution mechanisms and kinetics and predict the dissolution patterns in various realistic situations, considering wide properties of natural waters including acidic/alcaline waters

2025 International Conference on Bio-mediated and Bio-inspired Geotechnics (ICBBG2025)

General session: Fundamental research on biogeotechnics