Modification of All-in-One Solution for Improvement of 1m Sand Columns

The potential of microbially induced carbonate precipitation (MICP) for soil bio-improvement has been widely studied as an alternative to the traditional cementation by Portland cement. While multiple-phase injection techniques are commonly used for MICP treatment, they impose complexities and require a high number of injections. One of the latest developments in biocementation research area is using one-phase-low-pH MICP method as a more effective and efficient alternative to the traditional two-phase method. However, the one-phase-low-pH method has its challenges. The main challenge is delaying the start of carbonate precipitation to produce a homogenous distribution of cementation in soil matrixes. This study has tried to expand the lag phase with magnesium substitution for 20% calcium cations and decrease the initial temperature of reagents. These actions prolonged the lag phase by about five times, improved the crystal structure of carbonate precipitation and enhanced the transportability of bacteria in a 1 m length sand column. A modified injection strategy for all-in-one solution was introduced, and its capabilities were investigated in long sand columns. This new injection strategy provided a more uniform urea conversion, carbonate precipitation, and strength. It also decreased the required bacteria by 75% and minimized the necessity of pH adjustment and the initial low temperature of reagents.