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1. Engineered Water Repellency in Frost Susceptible Soils

   https://doi.org/10.1061/9780784484012.047  

   Uduebor, Micheal; Daniels, John; Naqvi, Mohammad Wasif; Cetin, Bora (March 2022, Geo-Congress 2022: Soil Improvement, Geosynthetics, and Innovative Geomaterials)

   Anne Lemnitzer, Ph.D.; Armin W. Stuedlein (Ed.)

   Selected papers from sessions of Geo-Congress 2022, held in Charlotte, North Carolina, March 20–23, 2022. Sponsored by the Society of Exploration Geophysicists and the Geo-Institute of ASCE. This Geotechnical Special Publication contains 66 peer-reviewed papers on geosynthetics, innovative geomaterials, and soil improvement techniques. Topics include: rigid inclusions and stone columns; soil stabilization; bio-grouting and bio-inspired solutions; geosynthetics; and innovative geomaterials and methods. GSP 331 will be valuable to practitioners and researchers working in the area of soil improvement. 

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2. Investigating the Frost Action in Soils

   https://doi.org/10.1061/9780784484067.027  

   Wasif Naqvi, Mohammad; Sadiq, Md. Fyaz; Cetin, Bora; Uduebor, Micheal; Daniels, John (March 2022, Geo-Congress 2022: Advances in Monitoring and Sensing; Embankments, Slopes, and Dams; Pavements; and Geo-Education)

   Anne Lemnitzer, Ph.D.; Armin W. Stuedlein (Ed.)

   Selected papers from sessions of Geo-Congress 2022, held in Charlotte, North Carolina, March 20–23, 2022. Sponsored by the Society of Exploration Geophysicists and the Geo-Institute of ASCE. This Geotechnical Special Publication contains 56 peer-reviewed papers on monitoring and sensing and embankments, dams, and slopes. Topics include: monitoring and remote sensing for geo-systems; geotechnics of resilient infrastructure; pavements; geotechnical engineering education; and data and software in geotechnical engineering. GSP 336 will be valuable to practitioners and researchers working in the areas of pavements and remote sensing and monitoring of geo-systems. 

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3. Investigating the Dissolution Behavior of Calcium Carbonate Bio-Cemented Sands

   https://doi.org/10.1061/9780784484012.040  

   Ribeiro, Bruna G.; Gomez, Michael G. (March 2022, Geo-Congress 2022 GSP 331)

   Microbially Induced Calcite Precipitation (MICP) is a bio-mediated cementation process that uses microbial enzymatic activity to catalyze the precipitation of CaCO3 minerals on soil particle surfaces and contacts. Extensive research has focused on understanding various aspects of MICP-treated soils including soil behavioral enhancements and process reaction chemistry, however, almost no research has explored the permanence of bio-cemented geomaterials. As the technology matures, an improved understanding of the longevity of bio-cementation improved soils will be critical towards identifying favorable field applications, quantifying environmental impacts, and understanding their long-term performance. In this study, a series of batch experiments were performed to investigate the dissolution kinetics of CaCO3-based bio- cemented sands with the specific aim of incorporating these behaviors into geochemical models. All batch experiments involved previously bio-cemented poorly graded sands that were exposed to different dissolution treatments intended to explore the magnitude and rate of CaCO3 dissolution as a function of acid type, concentration, initial pH, and other factors. During experiments, changes in solution pH and calcium concentrations indicative of CaCO3 dissolution were monitored. After experiments, aqueous measurements were compared to those simulated using two different dissolution kinetic frameworks. While not exhaustive, the results of these experiments suggest that the dissolution behavior of bio-cementation can be well-approximated using existing chemically controlled kinetic models, particularly when surrounding solutions are more strongly buffered. 

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4. Influence of the coefficient of uniformity on bio-cemented sands: a microscale investigation

   Reed, Marlee; Montoya, Brina M. (September 2023, Proceedings of the 8th International Symposium on DEFORMATION CHARACTERISTICS OF GEOMATERIALS)

   Viana da Fonseca, António; Ferreira, Cristiana (Ed.)

   Microbially induced carbonate precipitation (MICP) is a bio-mediated ground improvement technique that can increase soil stiffness and produce cohesion within granular material. Most experimental investigations on MICP-treated soils are performed on idealized granular materials. Evaluating a narrow range of particle sizes dismisses the potential influence of soil fabric on MICP treatment efficiency. Therefore, little is known regarding the influence of soil fabric on the level of improvement achievable post-MICP treatment. We investigate the influence of the coefficient of uniformity (Cu) on the level of improvement that can be obtained from MICP treatment. This study couples unconfined compression testing with microscale observations obtained from x-ray computed tomography (CT) of two sand mixtures with different Cu values. A soil column and CT specimen of each sand mixture were prepared and received the same number of MICP- injections. The shear wave velocity (Vs) of the soil columns was monitored to evaluate the increase in soil stiffness over time. After MICP treatment, the bio-cemented columns were subjected to unconfined compressive strength testing. Results indicate that for a similar mass of carbonate, the soil with a larger Cu experienced a greater increase in Vs but a lower maximum unconfined compressive strength. Through CT imaging, the soil with a smaller Cu was observed to have a more uniform distribution of carbonate within the sand matrix whereas the soil with a larger Cu has more sporadic MICP trends. This study elucidates the influence of soil fabric on the level of improvement that can be achieved through MICP treatment and assesses the reliability of x-ray CT scanning of MICP-treated sands with moderate carbonate content. 

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5. Mineralogy, morphology, and reaction kinetics of ureolytic bio-cementation in the presence of seawater ions and varying soil materials

   https://doi.org/10.1038/s41598-022-21268-3  

   Burdalski, Robert J.; Ribeiro, Bruna G.; Gomez, Michael G.; Gorman-Lewis, Drew (December 2022, Scientific Reports)

   Abstract Microbially-induced calcium carbonate precipitation (MICP) is a bio-cementation process that can improve the engineering properties of granular soils through the precipitation of calcium carbonate (CaCO 3 ) minerals on soil particle surfaces and contacts. The technology has advanced rapidly as an environmentally conscious soil improvement method, however, our understanding of the effect of changes in field-representative environmental conditions on the physical and chemical properties of resulting precipitates has remained limited. An improved understanding of the effect of subsurface geochemical and soil conditions on process reaction kinetics and the morphology and mineralogy of bio-cementation may be critical towards enabling successful field-scale deployment of the technology and improving our understanding of the long-term chemical permanence of bio-cemented soils in different environments. In this study, thirty-five batch experiments were performed to specifically investigate the influence of seawater ions and varying soil materials on the mineralogy, morphology, and reaction kinetics of ureolytic bio-cementation. During experiments, differences in reaction kinetics were quantified to identify conditions inhibiting CaCO 3 precipitation and ureolysis. Following experiments, scanning electron microscopy, x-ray diffraction, and chemical composition analyses were employed to quantify differences in mineralogical compositions and material morphology. Ions present in seawater and variations in soil materials were shown to significantly influence ureolytic activity and precipitate mineralogy and morphology, however, calcite remained the predominant CaCO 3 polymorph in all experiments with relative percentages exceeding 80% by mass in all precipitates. 

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