a Institute of Geotechnical Engineering, School of Transportation, Southeast University, Nanjing, 211189, China
b Jiangsu Key Laboratory of Low Carbon and Sustainable Geotechnical Engineering, Nanjing, 211189, China
c Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Hong Kong, China
d College of Civil Engineering and Architecture, Hainan University, Haikou, 570228, China
2024, 16(12): 5121-5134. doi:10.1016/j.jrmge.2024.07.005
Received: 2024-03-18 / Revised: 2024-06-03 / Accepted: 2024-07-15 / Available online: 2024-07-17
2024, 16(12): 5121-5134.
doi:10.1016/j.jrmge.2024.07.005
Received: 2024-03-18
Revised: 2024-06-03
Accepted: 2024-07-15
Available online: 2024-07-17
The application of microbially induced carbonate precipitation (MICP) in clayey soils has attracted much attention, and many studies used clay as an additive to enhance microbial mineralization efficiency in sandy soils. Within the sand-clay-bacteria-calcite system, the property and content of clay play crucial roles in affecting bacterial growth and calcite formation. More important, bentonite is particularly sensitive to changes in the geochemical environment. In this study, the sand-bentonite mixtures were treated by biostimulated MICP, aiming to provide insights into the behavior of this system. The bacterial activity and cementation pattern at different bentonite contents were evaluated through a series of tests such as enrichment tests, unconfined compressive strength (UCS) tests, cementation content measurements, mercury intrusion porosimetry (MIP) tests, scanning electron microscopy (SEM) observations, and energy dispersive X-ray spectroscopy (EDS) analyses. The findings showed that the bentonite presence promoted the enrichment of indigenous ureolytic bacteria, with lower bentonite levels enhancing ureolytic activity. Macroscopic and microscopic characterization indicated that the bentonite-coating sand structure was more conducive to the formation of large-sized calcite crystals capable of cementing soil particles compared to sand-supported and bentonite-supported structures. Additionally, excessive calcium ions (Ca2+) concentrations in the cementitious solution would lead to predominant calcite deposition on soil particle surfaces, contributing minimally to strength improvement.
Keywords: Microbially induced carbonate precipitation (MICP), Biostimulation, Sand-clay mixtures, Bacterial activity, Cementation pattern
Ningjun Jiang
Dr. Ningjun Jiang is currently a Full Professor and interim Vice Director of Graduate School at Southeast University (SEU), China. He received his PhD from University of Cambridge, UK. Prior to joining SEU, he was an assistant professor at University of Hawaii at Manoa, USA. His research areas include bio-mediated geotechnics, soil remediation, and ground improvement. Prof. Jiang has published more than 80 journal and conference papers. He has received multiple research fundings from National Natural Science Foundation of China, China Ministry of Science and Technology, and Hawaii Department of Transportation, etc. He is the recipient of several academic awards, including Fredlund Award in 2019, Acta Geotechnica Best Paper Award in 2020, Soils and Foundations Editorial Board Member Award in 2021, and 75th Géotechnique Anniversary Early Career Award in 2023. Prof. Jiang is an Executive Deputy Editor-in-Chief for the young journal Biogeotechnics. Previously, he was also an editorial member of Soils and Foundations and Environmental Geotechnics.