Sandy Soil Improvement through Microbially Induced Calcite Precipitation (MICP) by Immersion

Summary

Here, microbially induced calcite precipitation (MICP) technology is presented to improve soil properties by immersion.

Abstract

The goal of this article is to develop an immersion method to improve the microbially induced calcite precipitation (MICP) treated samples. A batch reactor was assembled to immerse soil samples into cementation media. The cementation media can freely diffuse into the soil samples in the batch reactor instead of cementation media being injected. A full contact flexible mold, a rigid full contact mold, and a cored brick mold were used to prepare different soil sample holders. Synthetic fibers and natural fibers were selected to reinforce the MICP-treated soil samples. The precipitated CaCO₃ in different areas of the MICP-treated samples was measured. The CaCO₃ distribution results demonstrated that the precipitated CaCO₃ was distributed uniformly in the soil sample by the immersion method.

Introduction

As a biological ground improvement technology, microbially induced calcite precipitation (MICP) is capable of improving engineering properties of soil. It has been used to enhance the strength, stiffness, and permeability of soil. The MICP technique has gained much attention for soil improvement worldwide^1,2,3,4. Carbonate precipitation naturally happens and can be induced by nonpathogenic organisms that are native to the soil environment⁵. The MICP biogeochemical reaction is driven by the existence of ureolytic bacte....

Protocol

NOTE: All relevant material used in the following procedures are non-hazardous. Personal protective equipment (safety glasses, gloves, lab coat, full length pants, closed-toe shoes) are still needed.

1. Preparation of bacteria solution

1. Preparation of growth medium (NH₄-YE medium)
   NOTE: The components of growth media per liter of deionized water are: 20 g of yeast extract; 10 g of (NH₄)₂SO₄; and 0.13 M Tris buffer (pH 9.0).
   1. Autoclave ingredients separately.
   2. Dissolve 20 g of yeast extract, and 10 g of (NH₄)₂SO₄ in 1 L of deio....

Results

Figure 7 shows the distribution of precipitated CaCO₃ throughout the MICP-treated sample. The MICP-treated sample was divided into three different areas. The CaCO₃ content in each area was tested by the acid washing method. To dissolve precipitated carbonates, the dry MICP-treated samples were washed in a HCl solution (0.1 M), then rinsed, drained, and oven-dried for 48 hours. The difference value between the masses of samples before and after acid washing was considere.......

Discussion

The MICP technique by immersion was presented in this paper. Soil samples were immersed into the batch reactor to get fully penetrated by cementation media in the MICP process. In this method, a full contact flexible mold, a rigid full contact mold, and a cored brick mold were applied to prepare MICP-treated samples.

Different molds can be designed for different geometry requirements. The fibrous structure of geotextile increased the contact area between sand and cementation media, which effec.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Ammonium Chloride, >99%	Bio-world	40100196-3 (705033)
Ammonium Sulfate	Bio-world	30635330-3
Calcium Chloride Dihydrate, >99%	Bio-world	40300016-3 (705111)
Nutrient Broth	Bio-world	30620056-3
Sodium Bicarbonate, >99%	Bio-world	41900068-3 (705727)
Sporosarcina pasteurii	American Type Culture Collection	ATCC 11859
Synthetic fiber	FIBERMESH	Fibermesh 150e3
Tris-Base, Biotechnology Grade, >99.7%	Bio-world	42020309-2 (730205)
Urea, USP Grade, >99%	Bio-world	42100008-2 (705986)
Yeast Extract	Bio-world	30620096-3 (760095)