ETDs

This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.

In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.

Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.

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Enzyme Induced Carbonate Precipitation (EICP) for Soil Improvement

Description
This dissertation presents an investigation of calcium carbonate precipitation via hydrolysis of urea (ureolysis) catalyzed by plant-extracted urease enzyme for soil improvement. In this approach to soil improvement, referred to as enzyme induced carbonate precipitation (EICP), carbonate minerals are precipitated within the soil pores, cementing soil particles together and increasing…

This dissertation presents an investigation of calcium carbonate precipitation via hydrolysis of urea (ureolysis) catalyzed by plant-extracted urease enzyme for soil improvement. In this approach to soil improvement, referred to as enzyme induced carbonate precipitation (EICP), carbonate minerals are precipitated within the soil pores, cementing soil particles together and increasing the dilatancy of the soil. EICP is a bio-inspired solution to improving the properties of cohesionless soil in that no living organisms are engaged in the process, though it uses a biologically-derived material (urease enzyme).

Over the past decade, research has commenced on biologically-mediated solutions like microbially induced carbonate precipitation (MICP) and biologically-inspired solutions like EICP for non-disruptive ground improvement. Both of these approaches rely upon hydrolysis of urea catalyzed by the enzyme urease. Under the right environmental conditions (e.g., pH), the hydrolysis of urea leads to calcium carbonate precipitation in the presence of Ca^(2+). The rate of carbonate precipitation via hydrolysis of urea can be up to 〖10〗^14 times faster than natural process.

The objective of this research was to ascertain the effectiveness of EICP for soil improvement via hydrolysis of urea (ureolysis) catalyzed by plant-extracted urease enzyme. Elements of this work include: 1) systematic experiments to identify an optimum EICP treatment solution; 2) evaluation of the mechanical properties of EICP-treated soil under different treatment conditions and with varying carbonate contents; 3) investigation of the potential for enhancing the EICP stabilization process by including xanthan gum, natural sisal fiber, and powdered of dried non-fat milk in the EICP treatment solution; and 4) bench-scale studies of the use of EICP to make sub-horizontal columns of cemented soil for soil nailing and vertical columns of cemented soil for foundation support. As part of this research, the effect of three preparation methods (mix-and-compact, percolation, and injection) was also examined as was the influence of the grain size of soil. The results of this study should help make the EICP technique an attractive option for geotechnical engineers for ground improvement and stimulate the development and use of other biogeotechnical techniques for civil engineering purposes.
ContributorsAlmajed, Abdullah A. (Author) / Kavazanjian, Edward (Thesis advisor) / Zapata, Claudia (Committee member) / Hamdan, Nasser M (Committee member) / Arizona State University (Publisher)
Created2017