3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item The effect of various particle size fractions of fly ash additions on the properties and performance of oil well cements(2019) Rongai, GladmoreFly ash as supplementary cementitious materials had reduced the total price of Portland cement and has reduced the greenhouse gas emissions resulting in a sustainable “green” concrete. This study investigates the effect of various particle size fractions of fly ash as additive to cement in various amount on the properties and performance of oil well cements. An investigation on the effects of the different particle size and the various compositions was made. The fly ash were separated using sieves laid on top of the other and were allowed to vibrate allowing sieving of the fly ash. Various sieve sizes were used including 25um, 38um, 45um, 53um, 68um, 75um as well as 90um respectively. The retained fly ashes within the sieves were tested for performance when mixed at 0.35 water to cement ratio. The fly ash - cement slurries were tested for their shear stress and rate, compression strength, as well as water loss for a specific particle size and in different compositions. Graphs were plotted to show the different performance of cement slurries at different particle size composition against shear rate and shear stress. Experiments were carried out to determine the performance of the different particle size composition on the compressive strength and water loss. AAS was also used to determine the chemical composition of the fly ash and cement. Higher and low compression strength were observed for 38um and 75um particle size of the fly ash, respectively. Low fly ash content (10%) showed better strength compared to 40 %. Rheology test showed that fly ash - cement slurries followed the Bingham plastic model. An increase in fly ash content (from 10% to 70%) decreases the apparent viscosity from 596.59 and 394.17Pa. Results also showed that higher content fly ash lowered the yield stress of cement mixture. Finally, highest rate of water loss was recorded for low fly ash content (10 %)Item Exploring the environmental impacts of fly ash on Eskom's business sustainability and sustainable development: a study on Kriel power station in Mpumalanga province of South Africa(2018) Rasimphi, Khuliso JamesFly ash generated at coal fired power stations is associated with various environmental impacts. The aim of this study was to particularly investigate alternative ways in which fly ash generated at Kriel Power Station can be managed effectively to minimize environmental impacts in order to ensure alignment with the notion of sustainable development. The study was primarily focused on exploring the impacts of Kriel Power Station’s fly ash as well as current fly management practices within the context of contemporary principles of environmental management and sustainable development. Quantitative and qualitative research methods were used for data collection. Purposive sampling was used as primary sampling procedure to select fitting sample from the study population. Data from structured questionnaire surveys, semi- structured interviews as well as existing records was used for data collection. This study has found that fly ash utilization is an ideal management practice which is aligned with sustainable development notion as compared to disposal to ash dams. Kriel Power Station’s fly ash was found to consist of various valuable elements which can be used for various industrial production purposes. The findings further suggest that the very same valuable chemical elements found in Kriel Power Station’s fly ash can cause adverse environmental impacts such as water, land and air pollution depending on the management approach. One of the key findings of this research is that fly ash utilization program is currently not well marketed in South Africa; and there is a need for all relevant stakeholders to work together to educate the public on the opportunities presented by fly ash. As part of concluding remarks, this study also suggested some enabling policies which can be established in order to optimize fly ash utilization from the regulator level (national level) to the generator and end user level (institutions). Recommendations on relevant future studies which can potentially be undertaken to explore adverse impacts as well as benefits of fly ash were also made.Item Coal fly ash waste management challenges in the South African power generation sector and possible recycling opportunities: a case study of Hendrina and Kendal power stations(2018) Ramagoma, Mbavhalelo JusticeSouth Africa will be dependent on coal for power generation for many decades to come, before a complete transition is achieved where more energy will be generated from non-fossil fuel sources. Through case studies of Hendrina and Kendal Power Stations, this study explored how the management of fly ash (FA) waste in South Africa can be improved to minimise its impact on the environment and human health and examined the potential recycling applications that can benefit local communities. The study drew insights from an environmental justice framework to examine the pollution impacts that FA is exposing to the local community. The environmental justice theory is based on the principle that all people have a right to live in an environment that enhances their wellbeing. Empirical evidence obtained from local community’s in-depth interviews revealed that FA is impacting on the health of communities by exposing them to respiratory and other illnesses and it is also affecting their livelihoods which primarily involves farming. A just transition theory was employed to examine potential socio economic opportunities that can be derived from FA recycling to fulfil redistributive measures that can reduce inequality and eradicate poverty in local communities. Some of Eskom’s power stations like Hendrina are nearing the end of their lifespan since their commissioning in the 1960’s and 1970’s. To aid a just transition, ash recycling was found to have the potential to address the socio economic situation of the power station’s employees and the local communities. The study found that local communities generally lack knowledge about coal ash recycling and need to be empowered and supported to partake in ash recycling ventures. The study argues that a shift in the ash recycling regime is needed in order to benefit local communities and facilitate a just transition to a clean energy production.