Publication Details |
| Category | Text Publication |
| Reference Category | Journals |
| DOI | 10.1007/s40996-025-01808-3 |
| Document | Shareable Link |
| Title (Primary) | The swelling characteristics of an unsaturated bio-cemented sand-bentonite mixture: Analyzing the effect of bacterial concentration and suction |
| Author | Niknam Safari Kouchi, E.; Nikooee, E.; Habibagahi, G.; Niazi, A.; Nagel, T. |
| Source Titel | Iranian Journal of Science and Technology-Transactions of Civil Engineering |
| Year | 2025 |
| Department | ENVINF |
| Volume | 49 |
| Page From | 6005 |
| Page To | 6025 |
| Language | englisch |
| Topic | T5 Future Landscapes |
| Supplements | Supplement 1 |
| Keywords | Suction; Osmotic; Soil water retention curve; Swelling; Biocementation; Sporosarcina pasteurii |
| Abstract | Swelling soils are among the most prevalent problematic soils worldwide. The presence of swelling soils beneath foundation of buildings, irrigation canals, pavements, railway tracks and other infrastructures threatens their proper functioning and integrity, due to the large volumetric deformation that these soils experience as a result of change in saturation. There are various traditional methods to reduce swelling potential of expansive soils, such as lime and cement treatment. However, eco-friendly techniques such as microbially-induced carbonate precipitation (MICP), favoring their lower CO2 footprint, have received great attention recently as a green and sustainable substitute to the traditional additives. Despite recent studies on the swelling potential of MICP treated soils, little is known on the effect of microbially induced carbonate precipitation on the soil swelling potential at different suction levels. It is, thus, crucial to understand the effect of saturation change and suction level on the swelling characteristics of bio-cemented soils. In this study, hence, free swelling tests were performed on biocemented sand-bentonite mixtures exposed to different suction levels applied using the osmotic technique. The soil water retention curve is a fundamental property for characterizing mechanical and hydraulic characteristics of unsaturated soils. Therefore, water retention properties of the bio-cemented swelling soil samples were also examined at different suction levels and bacterial density (i.e., different cell densities of Sporosarcina pasteurii). Based on free-swell tests, it was discovered that the combination of bacterial concentration and suction plays a crucial role in reducing soil swelling in biocemented soils. A minimum reduction of 67% in the free swell index of the sand-bentonite mixture was observed by treating the soil with a bacterial solution of OD = 1, regardless of the applied suction. XRD and SEM analysis of the treated samples pointed to the precipitated calcium carbonate crystals. Furthermore, electrical conductivity measurement and calcimeter test results provided further evidence on the role of MICP in stiffening the soil structure and soil aggregation by reducing double layer thickness and formation of calcite bridges among soil grains. |
| Persistent UFZ Identifier | https://www.ufz.de/index.php?en=20939&ufzPublicationIdentifier=31994 |
| Niknam Safari Kouchi, E., Nikooee, E., Habibagahi, G., Niazi, A., Nagel, T. (2025): The swelling characteristics of an unsaturated bio-cemented sand-bentonite mixture: Analyzing the effect of bacterial concentration and suction Iran. J. Sci. Technol.-Trans. Civ. Eng. 49 , 6005 - 6025 10.1007/s40996-025-01808-3 |
|