Year of Publication

2019

Season of Publication

Fall

Paper Type

Master's Thesis

College

College of Computing, Engineering & Construction

Degree Name

Master of Science in Civil Engineering (MSCE)

Department

Engineering

NACO controlled Corporate Body

University of North Florida. School of Engineering

First Advisor

Raphael Crowley

Second Advisor

Terri Ellis

Third Advisor

Donald Resio

Department Chair

Osama Jadaan

College Dean

William Klosermeyer

Abstract

Microbial induced calcite precipitation (MICP) was used to treat several sandboxes filled with naturally occurring beach sand collected from Atlantic Beach, FL. Unlike most previous MICP studies, a surface-spray technique was used to treat these sandboxes where relatively high-concentration bacteria solution and high concentration calcium chloride/urea solutions were applied directly to the boxes’ surfaces. Several different treatment combinations were tested whereby bacterial optical density, bacteria/urea/calcium chloride volume relative to void space, and bacteria/urea/calcium chloride ratio were manipulated. Treated sandboxes were tested for erodibility using a pocket erodometer and for calcification using a wash method. In addition, sandboxes were dissected after calcification/erosion testing to examine calcification depth. Results showed that higher optical densities, higher bacteria quantities relative to void volume, and higher bacteria quantities relative to urea led to higher calcification. By maximizing these three variables, calcium carbonate precipitation of approximately 6% was achieved after one treatment. After five treatments, calcification approached 15%. However, even with significant calcification like this, erodibility improvements were relatively moderate. In addition, correlations were developed that appeared to show indirect relationships between erodibility and calcite content; and direct relationships between calcification depth and calcite content. Overall, results seem to present a roadmap for upscaling microbial treatment for erosion control – generally, “more is better” and adding as much bacteria, urea, and calcium carbonate as possible to soil appears to produce the most erosion resistance.

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