Calcite seed-assisted microbial induced carbonate precipitation (MICP).

Jennifer Zehner,Pawel Sikorski,Anja Røyne,Amitava Mukherjee

doi:10.1371/journal.pone.0240763

Abstract

Microbial-induced calcium carbonate precipitation (MICP) is a biological process inducing biomineralization of CaCO3. This can be used to form a solid, concrete-like material. To be able to use MICP successfully to produce solid materials, it is important to understand the formation process of the material in detail. It is well known that crystallization surfaces can influence the precipitation process. Therefore, we present in this contribution a systematic study investigating the influence of calcite seeds on the MICP process. We focus on the changes in the pH and changes of the optical density (OD) signal measured with absorption spectroscopy to analyze the precipitation process. Furthermore, optical microscopy was used to visualize the precipitation processes in the sample and connect them to changes in the pH and OD. We show, that there is a significant difference in the pH evolution between samples with and without calcite seeds present and that the shape of the pH evolution and the changes in OD can give detailed information about the mineral precipitation and transformations. In the presented experiments we show, that amorphous calcium carbonate (ACC) can also precipitate in the presence of initial calcite seeds and this can have implications for consolidated MICP materials.

Highlights

Biocementation is a biological process, which improves the engineering properties of a granular medium by biomineralization
The pH evolution as well as the OD at 750 nm (OD750nm) curves for CaCO3 precipitation, induced by hydrolysis of urea by S. pasteurii, in samples that did not contain calcite seeds are shown in Fig 1a and 1b
We presented a systematic study investigating the influence of calcite seeds on the crystallization processes of CaCO3 in microbial induced calcite precipitation (MICP)

Summary

Introduction

Biocementation is a biological process, which improves the engineering properties of a granular medium by biomineralization. Biomineralized CaCO3 fills pores and bind the granular medium together, which results in an increase of strength and stiffness and reduce the permeability of the granular medium [1]. One of the most commonly used process to achieve biocementation is microbial induced calcite precipitation (MICP). MICP has been successfully used for soil stabilization [1, 2]. Using MICP for soil stabilization reduces the environmental impact of ground improvement, since conventional ground improvement techniques often have a high impact on the environment [3]. MICP has the potential to replace conventional concrete as a building material in some applications.

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