Civil Engineering
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The Department of Civil Engineering has strong affiliation with the Western Transportation Institute (WTI) and the Center for Biofilm Engineering (CBE), a graduated NSF research center. The department is also affiliated with a Montana Department of Transportation Design Unit located on the MSU campus.
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Item Biomineralization of Plastic Waste to Improve the Strength of Plastic-Reinforced Cement Mortar(2021-04) Kane, Seth; Thane, Abby; Espinal, Michael; Lunday, Kendra; Armagan, Hakan; Phillips, Adrienne J.; Heveran, Chelsea M.; Ryan, Cecily A.The development of methods to reuse large volumes of plastic waste is essential to curb the environmental impact of plastic pollution. Plastic-reinforced cementitious materials (PRCs), such as plastic-reinforced mortar (PRM), may be potential avenues to productively use large quantities of low-value plastic waste. However, poor bonding between the plastic and cement matrix reduces the strength of PRCs, limiting its viable applications. In this study, calcium carbonate biomineralization techniques were applied to coat plastic waste and improved the compressive strength of PRM. Two biomineralization treatments were examined: enzymatically induced calcium carbonate precipitation (EICP) and microbially induced calcium carbonate precipitation (MICP). MICP treatment of polyethylene terephthalate (PET) resulted in PRMs with compressive strengths similar to that of plastic-free mortar and higher than the compressive strengths of PRMs with untreated or EICP-treated PET. Based on the results of this study, MICP was used to treat hard-to-recycle types 3–7 plastic waste. No plastics investigated in this study inhibited the MICP process. PRM samples with 5% MICP-treated polyvinyl chloride (PVC) and mixed type 3–7 plastic had compressive strengths similar to plastic-free mortar. These results indicate that MICP treatment can improve PRM strength and that MICP-treated PRM shows promise as a method to reuse plastic waste.Item Kinetics of Calcite Precipitation by Ureolytic Bacteria under Aerobic and Anaerobic Conditions(2019-05) Mitchell, Andrew C.; Espinosa-Ortiz, Erika J.; Parks, Stacy L.; Phillips, Adrienne J.; Cunningham, Alfred B.; Gerlach, RobinThe kinetics of urea hydrolysis (ureolysis) and induced calcium carbonate (CaCO3) precipitation for engineering use in the subsurface was investigated under aerobic conditions using Sporosarcina pasteurii (ATCC strain 11859) as well as Bacillus sphaericus strains 21776 and 21787. All bacterial strains showed ureolytic activity inducing CaCO3 precipitation aerobically. Rate constants not normalized to biomass demonstrated slightly higher-rate coefficients for both ureolysis (kurea) and CaCO3 precipitation (kprecip) for B. sphaericus 21776 (kurea=0.10±0.03 h−1, kprecip=0.60±0.34 h−1) compared to S. pasteurii (kurea=0.07±0.02 h−1, kprecip=0.25±0.02 h−1), though these differences were not statistically significantly different. B. sphaericus 21787 showed little ureolytic activity but was still capable of inducing some CaCO3 precipitation. Cell growth appeared to be inhibited during the period of CaCO3 precipitation. Transmission electron microscopy (TEM) images suggest this is due to the encasement of cells and was reflected in lower kurea values observed in the presence of dissolved Ca. However, biomass regrowth could be observed after CaCO3 precipitation ceased, which suggests that ureolysis-induced CaCO3 precipitation is not necessarily lethal for the entire population. The kinetics of ureolysis and CaCO3 precipitation with S. pasteurii was further analyzed under anaerobic conditions. Rate coefficients obtained in anaerobic environments were comparable to those under aerobic conditions; however, no cell growth was observed under anaerobic conditions with NO−3, SO2−4 or Fe3+ as potential terminal electron acceptors. These data suggest that the initial rates of ureolysis and ureolysis-induced CaCO3 precipitation are not significantly affected by the absence of oxygen but that long-term ureolytic activity might require the addition of suitable electron acceptors. Variations in the ureolytic capabilities and associated rates of CaCO3 precipitation between strains must be fully considered in subsurface engineering strategies that utilize microbial amendments.Item Bulk electric conductivity response to soil and rock CO2 concentration during controlled CO2 release experiments: Observations & analytic modeling(2015-09) Jewell, Scott; Zhou, Xiaobing; Apple, Martha E.; Dobeck, Laura M.; Spangler, Lee H.; Cunningham, Alfred B.To develop monitoring technologies for geologic CO2 storage, controlled CO2 release experiments at the Zero Emissions Research and Technology (ZERT) site in Bozeman, Montana, USA, were carried out in 2009-2011. To understand the impact on the electric properties of soil and sediment rock due to possible CO2 leakage, we have developed an analytical model to explain and predict the electric conductivity (EC) for CO2 impacted soil and sedimentary rock. Results from the model were compared with the measurements at the ZERT site during 2009–2011 and the CO2-Vadose Project site in France in 2011-2012 after model calibration at each site. The model was calibrated using the saturation (n) and cementation (m) exponents contained in Archie's equation, and a chemistry coefficient (pKc) as tuning parameters that minimized the misfit between observed and modeled soil/rock bulk conductivity data. The calibration resulted in n=3.15, m=2.95, and pKc=4.7 for the ZERT site, which was within the range of values in the literature. All the ZERT data sets had rms errors of 0.0115-0.0724. For the CO2-Vadose site, calibration resulted in n=3.6-9.85 and m=2.5-4.2, pKc=4.80-5.65, and the rms error of 0.0002-0.0003; the cementation exponents were consistent with the literature. These results found that the model predicted the bulk EC reasonably well in soil and rock once the unmeasurable model parameters (n, m, and pKc) were calibrated.Item Whole cell kinetics of ureolysis by Sporosarcina pasteurii(2015-06) Lauchnor, Ellen G.; Topp, D. M.; Cunningham, Alfred B.; Gerlach, RobinAims Ureolysis drives microbially induced calcium carbonate precipitation (MICP). MICP models typically employ simplified urea hydrolysis kinetics that do not account for cell density, pH effect or product inhibition. Here, ureolysis rate studies with whole cells of Sporosarcina pasteurii aimed to determine the relationship between ureolysis rate and concentrations of (i) urea, (ii) cells, (iii) and (iv) pH (H+ activity). Methods and Results Batch ureolysis rate experiments were performed with suspended cells of S. pasteurii and one parameter was varied in each set of experiments. A Michaelis–Menten model for urea dependence was fitted to the rate data (R2 = 0·95) using a nonlinear mixed effects statistical model. The resulting half-saturation coefficient, Km, was 305 mmol l−1 and maximum rate constant, Vmax, was 200 mmol l−1 h−1. However, a first-order model with k1 = 0·35 h−1 fit the data better (R2 = 0·99) for urea concentrations up to 330 mmol l−1. Cell concentrations in the range tested (1 × 107–2 × 108 CFU ml−1) were linearly correlated with ureolysis rate (cell dependent = 6·4 × 10−9 mmol CFU−1 h−1). Conclusions Neither pH (6–9) nor ammonium concentrations up to 0·19 mol l−1 had significant effects on the ureolysis rate and are not necessary in kinetic modelling of ureolysis. Thus, we conclude that first-order kinetics with respect to urea and cell concentrations are likely sufficient to describe urea hydrolysis rates at most relevant concentrations. Significance and Impact of the Study These results can be used in simulations of ureolysis driven processes such as microbially induced mineral precipitation and they verify that under the stated conditions, a simplified first-order rate for ureolysis can be employed. The study shows that the kinetic models developed for enzyme kinetics of urease do not apply to whole cells of S. pasteurii.