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It is the intent of this research to determine the feasibility of utilizing industrial byproducts in cementitious systems in lieu of Portland Cement to reduce global CO2 emissions. Class C and Class F Fly Ash (CFA and FFA, respectively) derived from industrial coal combustion were selected as the replacement materials for this study. Sodium sulfate and calcium oxide were used as activators. In Part 1 of this study, focus was placed on high volume replacement of OPC using sodium sulfate as the activator. Despite improvements in heat generation for both CFA and FFA systems in the presence of sulfate, sodium sulfate was found to have adverse effects on the compressive strength of CFA mortars. In the CFA mixes, strength improved significantly with sulfate addition, but began to decrease in strength around 14 days due to expansive ettringite formation. Conversely, the addition of sulfate led to improved strength for FFA mixes such that the 28 day strength was comparable to that of the CFA mixes with no observable strength loss. Maximum compressive strengths achieved for the high volume replacement mixes was around 40 MPa, which is considerably lower than the baseline OPC mix used for comparison. In Part 2 of the study, temperature dependency and calcium oxide addition were studied for sodium sulfate activated systems composed of 100% Class F fly ash. In the presence of sulfate, added calcium increased reactivity and compressive strength at early ages, particularly at elevated temperatures. It is believed that sulfate and calcium react with alumina from fly ash to form ettringite, while heat overcomes the activation energy barrier of fly ash. The greatest strengths were obtained for mixes containing the maximum allowed quantity of calcium oxide (5%) and sodium sulfate (3%), and were around 12 MPa. This is a very low compressive strength relative to OPC and would therefore be an inadequate substitute for OPC needs.
ContributorsTweedley, Shannon Elizabeth (Author) / Neithalath, Narayanan (Thesis director) / Mamlouk, Michael (Committee member) / Civil, Environmental and Sustainable Engineering Programs (Contributor) / Barrett, The Honors College (Contributor) / School of Sustainable Engineering and the Built Environment (Contributor)
Created2014-05
Description
The civil engineering curriculum includes the engineering fields of environmental, geotechnical, hydrology, structural, and transportation. A particular focus on the structural engineering curriculum outline involves courses in mathematics, engineering mechanics, structural analysis, and structural design. The core structural analysis and design course at Arizona State University (CEE 321) is a transition course to connect realistic structural design and analysis concepts to an engineering foundation created by the first and second year mathematics and mechanics courses. CEE 321 is styled after a flipped classroom model and students are assessed through quizzes, midterms, design projects, and a final exam. Student performance was evaluated for the Spring 2013 and Fall 2013 semesters through an error analysis technique designed to categorize student mistakes based on type of error and related topic. This analysis revealed that student's basic engineering mechanics skills improved throughout the course as well as identified the areas that students struggle in. The slope-deflection and direct stiffness methods of analysis and calculating cross-sectional properties are the primary areas of concern. Using appropriate technology in the engineering classroom has the potential to enhance the learning environment and address the areas of inadequacy identified by the performance analysis. A survey of CEE 321 students demonstrated that technology is a highly integrated and useful portion of student's lives. Therefore, the engineering classroom should reflect this. Through the use of analysis and design software, students are able to begin to develop design intuition and understanding while completing realistic engineering projects in their third year of undergraduate studies. Additionally, incorporating internet resources into and outside of the classroom allows students to be connected to course content from any web-enabled device of their choice. Lecture videos posted online covering the course content were requested by many CEE 321 students and are an emerging resource that supplements the flipped classroom model. The availability of such a tool allows students to revisit concepts that they do not understand or pause, rewind, and replay the lectures when necessary. An expansion of the structural analysis and design online lecture videos for CEE 321 are expected to address and improve the areas that students struggle in as identified by the error analysis.
ContributorsMika, Krista Nicole (Author) / Rajan, Subramaniam (Thesis director) / Mamlouk, Michael (Committee member) / Civil, Environmental and Sustainable Engineering Programs (Contributor) / Barrett, The Honors College (Contributor)
Created2013-12