Publication Date

8-2023

Date of Final Oral Examination (Defense)

June 2023

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Civil Engineering

Department

Civil Engineering

Supervisory Committee Chair

Bhaskar Chittoori, Ph.D., P.E.

Supervisory Committee Member

Nick Hudyma, Ph.D., PE

Supervisory Committee Member

Michael J. Dickey, P.E.

Abstract

Microbially Induced Calcite Precipitation (MICP) has emerged as a promising technique for soil stabilization, traditionally involving the preparation and mixing of treatment solutions with the soil. However, this thesis explores a novel approach of applying MICP by directly mixing dry chemical compounds into the soil and subsequently adding water. This alternative method offers potential advantages in terms of convenience, ease of implementation, and cost savings.

The objective of this research is to investigate the applicability of dry mixing protocols for MICP in soil stabilization. Through comprehensive experimentation, three different dry protocols were developed and applied to five different soils. The effectiveness of these protocols was evaluated by monitoring pH levels, calcium carbonate precipitation, and free swell indexes.

The findings demonstrated that the dry mixing protocols resulted in significant calcium carbonate precipitation, comparable to or even surpassing that of the conventional protocol after some rounds of treatment. This research provides valuable insights into the feasibility and efficacy of employing MICP through dry mixing methods.

The innovative approach of directly mixing dry chemical compounds into the soil and subsequently adding water presents numerous benefits in terms of convenience and cost-effectiveness. By eliminating the need for preparing and mixing treatment solutions, this approach streamlines the application process, facilitating large-scale implementation.

This research contributes to the advancement of MICP techniques and offers a practical alternative for the soil stabilization industry. The new application method has the potential to revolutionize soil stabilization practices, providing a more efficient and effective solution for various geotechnical applications. Further development and implementation of dry mixing protocols in the industry can lead to significant advancements in soil stabilization practices, ultimately enhancing infrastructure durability. Both the conventional protocol and dry protocol-1 exhibited a similar trend of calcite precipitation as the treatment rounds progressed. In both cases, there was a gradual increase in the amount of calcium carbonate with each successive round of treatment. However, it is important to note that while the conventional protocol resulted in the highest overall calcium carbonate precipitation after seven treatment rounds, dry protocol-2 and dry protocol-3 displayed a distinct pattern. These dry protocols initially generated a relatively substantial amount of calcium carbonate precipitation in the early treatment rounds, but as the rounds progressed, the precipitation either declined or showed minimal increments. This observation underscores the differential behavior of the dry protocols compared to the conventional protocol regarding calcium carbonate precipitation throughout the treatment process.

DOI

https://doi.org/10.18122/td.2133.boisestate

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