Improvement of uniformity of biocemented sand column using CH₃COOH-buffered one-phase-low-pH injection method

• Main Authors: Yang, Yang, Chu, Jian, Liu, Hanlong, Cheng, Liang
• Other Authors: School of Civil and Environmental Engineering
• Format: Article
• Language: English
• Published: 2022
• Subjects: Engineering::Civil engineering; Crystal Shape; CH3COOH Buffered
• Online Access: https://hdl.handle.net/10356/162156
• Institution: Nanyang Technological University

Biocement based on a Microbially Induced Calcite Precipitation (MICP) process has emerged to be a promising alternative to cement for soil improvement. A two-phase injection method is commonly used for the MICP treatment of granular soil. However, the samples treated using this method may not be uniform. Recently, an acidified one-phase-low-pH injection method was developed using HCl as a buffer. This method could improve the uniformity of the MICP treatment to a certain extent. However, the distance in which the soil could be treated uniformly is still limited. This paper presents a CH3COOH-buffered one-phase-low-pH method which could improve the uniformity of biocement treatment considerably compared with the one-phase-low-pH method based on HCl. The key feature of this method is to create a much longer lag duration; thus, the biocementation process can be delayed and allow the all-in-one solution to be distributed more uniformly in soil within the lag duration. The uniformity of MICP-treated 1-m and 2-m sand columns was evaluated by comparing the unconfined compressive strengths and the calcium carbonate contents measured at different locations along the sand columns. The test results show that the proposed method is much more effective in improving the uniformity of the MICP treatment though a significant increase in the lag duration, given the other conditions the same.