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- All Subjects: Medellin
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Description
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 purpose of this text is to research and specify inequities present within three South American cities; Medellin, Columbia, Mexico City, Mexico, and Rio de Janeiro, Brazil. This research then considers specific neighborhoods within these cities that have become underprivileged as a result of the inequities, and analyzes architectural insertions that have been placed in these communities in hopes of balancing the inequities secluding the communities from the rest of the city. With the information gathered from the three case study cities, another city, Tijuana, Mexico, is examined and ascertained as to what type of inequities are present. Using the methodology implemented in the case studies, a specific architectural insertion is proposed in relation to the problems at hand, with the intent of balancing the inequalities present in an underprivilege neighborhood in Tijuana. Ultimately, the text strives to demonstrate the power of architectural insertions within a community, while highlighting the importance of the effects upon the daily lives of the inhabitants, as well as the dynamics within the community and greater city.
ContributorsBorie, Isabelle Ethelbah (Author) / Spellman, Catherine (Thesis director) / Vekstein, Claudio (Committee member) / Hejduk, Renata (Committee member) / The Design School (Contributor) / School of Sustainable Engineering and the Built Environment (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05