Faculty of Engineering and Built Environment
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Item Evaluating the performance of high-volume fly ash (HVFA) concrete, for South African fly ash(IJRTEM, 2016-07) Zulu, Sabelo; Allopi, DhirenDue to the benefits provided by the usage of FA in concrete, the usage of HVFA concrete is increasing within the concrete industry. This study looked at the effects of increasing the content of FA in concrete, beyond the conventional 30% amount, to find an optimum amount suitable for use in concrete structures, without compromising the quality of concrete. Concrete mixes of 25MPa, 35MPa and 50MPa with FA partially substituting the cement at 30%, 40%, 50% and 60%, were produced and numerous concrete properties were evaluated in a laboratory environment, to determine an optimum amount of HVFA that can be used and still obtain better or comparable concrete to ordinary concrete. Concrete testing for compressive strength, durability, slump, setting time and drying shrinkage was performed at laboratories over a period of one year. Also a cost comparison between the ordinary concrete and FA concrete was done. Test results showed that HVFA concrete can perform well in structures with good compressive strength and durability result even if the amount of cement is less than of fly ash. It can also be economical to utilize HVFA concrete, especially in larger project.Item Effects and benefits of using high content of fly ash in concrete(Thomson Reuters, 2016-01) Zulu, Sabelo; Allopi, DhirenThe usage of fly ash products by the South African cement and construction industries has saved the country over 6 million tons of harmful greenhouse gas emissions. The recycling of it as cement extenders provides an immediate benefit for the environment while still improving the quality of concrete, and increasing the amount used in concrete can promote sustainable development. This study evaluated properties of 35MPa/9,5mm concrete with fly ash substituted at 30%, 40%, 50% and 60%. Increasing the fly ash content can result in more workable and less permeable concrete. The compressive strength and durability index results showed that the fly ash content can be increased beyond 50% and still achieve the required strength and produce durable concrete. Substituting high volumes of cement with fly ash in concrete can provide good quality concrete and a relief to the environment without compromising the quality and cost of concrete.Item Influence of high content fly ash on concrete durability(IJEIT, 2014-01) Allopi, Dhiren; Zulu, SabeloAbstract - The use of fly ash products by the South African cement and construction industries has saved the country over 6 million tons of harmful greenhouse gas emissions. Fly ash is an industrial by-product that is normally consigned to landfills and the re-use of it as cement extenders provides an immediate benefit for the environment while still improving the quality of concrete. Fly ash blended cements in concrete perform better than pure cement in providing better concrete properties. Current specifications limit the use of fly ash in concrete to 30%, although an increase of this amount can be very beneficial in concrete structures, economically and environmentally. In South Africa the durability index of concrete is commonly determined by performing the Oxygen Permeability test, Water Sorptivity test and Chloride Conductivity test, developed by the Universities of Cape Town and the Witwatersrand. Performing these tests in this study, the results obtained showed that concrete mixes with fly ash content that is higher than the specification limit can result in concrete with acceptable good durability qualities, and with age, the durability qualities are improved due to pozzolanic reactions. Substituting high volumes of cement with fly ash in concrete can provide high quality concrete and a relief in the environment without compromising the quality of concrete.