Ground Improvement with a Single Injection of a High-Performance All-in-one MICP Solution

Abstract

All-in-one injection strategy has been developed recently as an efficient method in microbially induced carbonate precipitation (MICP). In this method, engineers try to delay the beginning of precipitation and consequently distribute reagents homogeneously on a soil mass. In this article, a series of experiments have been carried out to modify all-in-one solution strategy and promote its uniformity. Primarily, the concentration of all-in-one solutions was optimized and the result showed that all-in-one solution with a 2 M concentration of urea/calcium chloride was completely consumed. The short columns treated by one-time one-pore volume (PV) injection of 2 M all-in-one solution provided approximately 450 kPa in UCS test. In the second step, magnesium substitution for calcium was investigated to improve the strength and homogeneity of biocementation. This substitution raised the UCS by approximately 70%, and 800 kPa was acquired. XRD analysis confirmed that Mg²⁺ changes the mineralogy of precipitation from vaterite to aragonite. Hence, the higher strength of columns treated with the magnesium-substituted solutions is attributed to the higher hardness of aragonite crystals than that of vaterite. Finally, the bacterial transport of all-in-one solutions showed that magnesium substitution for 20% of calcium cations, enhances its potential to provide a homogeneous biocement on large-scale projects.

Keywords:

• All-in-one solution
• biocementation
• ground improvement
• magnesium addition
• microbially induced carbonate precipitation (MICP)
• bacterial transportability

Disclosure statement

The authors declare that the research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest.

Data availability statement

All data, photos, and analyses presented in this article are available from the corresponding author by request.

Additional information

Funding

The work was supported by NSFC Major International Joint Research Project POW3M (51920105013), NSFC-National Outstanding Youth Science Fund Project (52122109), Key Laboratory of Ministry of Education for Coastal Disaster and Protection, Hohai University (202210), Jiangsu Distinguished Professor Program, and Jiangsu Province ‘‘Six Talent Peak’’ program (XCL-111).