# A One-Phase Injection Method with Dual Inhibition for Improving the Strength and Uniformity of MICP

## TL;DR

This study introduces a dual inhibition method to improve the strength and uniformity of calcium carbonate in microbial-induced processes for geotechnical applications.

## Contribution

The novel dual inhibition strategy synergistically lowers pH and temperature to enhance CaCO3 uniformity and strength in a single-phase injection method.

## Key findings

- The minimum pH for flocculation increased from ~4.5 at 40 °C to ~6.0 at 10 °C under dual inhibition.
- After four treatment cycles, CaCO3 content at 10 °C increased by 53%, with compressive strength reaching 2.5 MPa.
- XRD analysis showed calcite as the dominant phase (85–90%) with minor vaterite.

## Abstract

The formation and spatial uniformity of calcium carbonate (CaCO3) are critical for evaluating the effectiveness of microbial-induced calcium carbonate precipitation (MICP) in geotechnical applications. In recent years, the single-phase injection method has emerged as a promising alternative to traditional two-phase processes by addressing the issue of uneven CaCO3 distribution. This study proposes a dual inhibition strategy that delays the mineralization reaction by synergistically lowering pH and temperature, thereby promoting uniform precipitation and enhanced compressive strength in cemented sand columns. A series of experiments, including bacterial growth, aqueous reaction, sand column reinforcement, and microstructural characterization, were conducted. Results show that the minimum pH required for flocculation increases from ~4.5 at 40 °C to ~6.0 at 10 °C. Under dual inhibition, the lag period effectively improved the spatial uniformity of CaCO3 and enabled complete calcium utilization within 24 h. After four treatment cycles, the CaCO3 content at 10 °C increased by 53%, and the unconfined compressive strength reached 2.5 MPa, a 50% improvement over the 40 °C condition. XRD analysis confirmed that calcite was the dominant phase (85–90%), accompanied by minor vaterite. These findings demonstrate the adaptability and efficiency of the dual inhibition method across temperature ranges, providing a cost-effective solution for broader engineering applications.