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Enzyme-Induced Carbonate Precipitation Utilizing Fresh Urine and Calcium-Rich Zeolites

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Enzyme-induced carbonate precipitation (EICP) is a biocementation technique that produces comparatively fewer carbon dioxide emissions than traditional cementation. However, the use of synthetic reagents for EICP is costly, and the process produces an ammonium byproduct which is a harmful pollutant. This study utilizes fresh urine as a source of urea…

Enzyme-induced carbonate precipitation (EICP) is a biocementation technique that produces comparatively fewer carbon dioxide emissions than traditional cementation. However, the use of synthetic reagents for EICP is costly, and the process produces an ammonium byproduct which is a harmful pollutant. This study utilizes fresh urine as a source of urea and calcium-rich zeolites as an ammonium adsorbent and a source of calcium ions for the EICP cementation technique. Batch hydrolysis and adsorption experiments were conducted to determine the effects of zeolite type, zeolite form, and solution composition on ammonium adsorption and calcium release. Cementation experiments were then conducted to determine the effects of different hydrolysis and adsorption times on ammonium adsorption and calcium carbonate precipitation. The results showed that calcium-rich chabazite could be used as a source of calcium ions and as an effective adsorbent of ammonium for EICP. Additionally, synthetic, fresh urine and real, fresh urine had comparable ammonium adsorption and calcium release trends. Finally, inclusion of a pre-hydrolysis step reduced the ammonium adsorption and calcium release, but longer adsorption times lead to calcium carbonate precipitation outside of the sand column, which is an undesirable outcome for soil biocementation; even with this limitation, the calcium carbonate content of sand columns ranged from 0.48% to 0.92%, which signifies the potential of the proposed process for cementation, given a higher initial concentration of urea.
ContributorsCrane, Lucas Christopher (Author) / Boyer, Treavor (Thesis director) / Hamdan, Nasser (Committee member) / Civil, Environmental and Sustainable Eng Program (Contributor) / School of Sustainable Engineering & Built Envirnmt (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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The effect of UV-treated plastic reinforcement in cement-based materials

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The preceding paper analyzes the effects of UV radiation in plastic reinforcement and its effects on the fracture properties of cement-based materials. Three point tests were performed on notched beams, which called for the consideration of the Type II Size Effect. A comparison of the ductility of beams with and…

The preceding paper analyzes the effects of UV radiation in plastic reinforcement and its effects on the fracture properties of cement-based materials. Three point tests were performed on notched beams, which called for the consideration of the Type II Size Effect. A comparison of the ductility of beams with and without polyethylene plastic powder reinforcement was done through the calculation of the fracture parameters Gf and cf, which represent the initial fracture energy and the characteristic length respectively. Although there was an observed increase in ductile behavior and properties in beams with polyethylene reinforcement, there did not seem to be a significant effect caused by the UV radiation. The hydrophilicity of the polyethylene powder was successfully increased through UV radiation and validated through water retention tests, which showed that the UV-treated polyethylene was retaining more water than the non-treated polyethylene, yet there was no extra increase in ductility of the cement beams compared to using non-treated polyethylene. The Type II Size Effect analysis was performed and compared to the stress analysis results of the experiment. For future research, it is recommended that a higher volume of polyethylene per 1000 grams of cement powder be used, as well as increasing the strength of the UV chamber to achieve a larger increase in the hydrophilicity of the polyethylene. Also, perhaps using more precise equipment to cut the notches in the beams would be helpful in ensuring that all specimens are identical and there is no error in notch depth caused by inaccurate use of the hacksaw or radial saw. Further experiments will be conducted.
ContributorsMardambek, Karim (Author) / Hoover, Christian (Thesis director) / Kazembeyki, Maryam (Committee member) / Civil, Environmental and Sustainable Eng Program (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2019-05