Theses and dissertations (Engineering and Built Environment)
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Item Characterisation of concrete with expanded polystyrene, eggshell powder and non-potable water : a case study(2023-05) Mncwango, Bonke; Allopi, DhirenUrbanisation has brought many benefits but it has also highlighted the global lack of housing alongside global natural resource scarcity. Lack of housing on the surface appears to be a singular problem, however in reality it represents a number of society’s biggest challenges such as crime, pollution (as a result of inadequate waste disposal strategies), unhygienic living conditions, as well as numerous health problems. Governments across the world have made various attempts at addressing the issue of lack of housing, including embarking on large scale social and public housing initiatives, building smaller homes for the homeless, as well as removing certain regulatory barriers to allow more houses to be built at a reduced timeframe. These advances have assisted many individuals and families globally, however, there are still many individuals and families that government housing-aid or housing initiatives have not yet reached. These individuals and families are faced with solving their housing crisis on their own, with their own resources. Globally, concrete remains a supreme building material in the construction industry and therefore is a primary factor of consideration for solving the housing crisis, especially for those who have no financial assistance or aid from government. Concrete’s composition is simple: cement, fine aggregate, coarse aggregate and water. The intricate interaction between all four components is meant to stand the test of time. Unfortunately, it is not only the earth’s diminishing natural resource reserves which are causing a decline in the popularity of conventionally produced concrete, but it is also the irreparable harm that it is causing to the environment. The process of concrete production requires large volumes of cement, and cement remains one of the biggest producers of carbon dioxide. Carbon dioxide is a greenhouse gas which in excessive amounts creates a cover that traps the sun’s heat energy in the atmosphere. Another major criticism of conventional concrete is the requirement that it be produced with clean water which is of a drinkable standard. This criticism is justified when considering the extreme water shortages that are experienced by many low to middle income countries around the world. The amount of financial and human resources that local authorities invest in cleansing water to bring it to a drinkable standard is often overlooked. It is obvious that it is less expensive to use water directly from a river in its natural state than using it after it has undergone numerous cleansing processes by local authorities. There have been a notable number of advances in making concrete more resource-efficient and environmentally friendly. These include the advent of lightweight concretes such as expanded polystyrene concrete. Expanded polystyrene concrete not only saves the amount of aggregate that would normally be required in conventional concrete, it also has excellent acoustic and thermal properties, thereby reducing energy consumption which in turn saves money. However, even with such excellent properties, expanded polystyrene concrete still fails to address two of concrete’s major criticisms which are related to the amount of cement used as well as the amount of clean potable water required for mixing. Therefore, by building on the qualities of expanded polystyrene concrete, this research investigates the potential of lowering the amount of cement required in a concrete mix through the use of eggshell powder. Eggshells are a waste product found everywhere in the world and are readily available in almost limitless quantities. The use of eggshells in concrete to lower the amount of cement required will not only achieve a reduction in the amount of carbon dioxide that is produced in the process of producing concrete, it will also assist in contributing toward solving the escalating waste disposal crisis that currently exists for many waste types such as eggshells. It is common for communities to reside close to a river or a natural flowing watercourse, so this research included river water as a variable. Four different concrete mix scenarios were tested to ascertain through experimentation whether the strength properties of concrete that contains expanded polystyrene, eggshell powder and natural river water in various proportions could in any way compare to a conventionally produced concrete mix. In order to comprehensively study material behaviour in this case, sieve analysis, bulk density, fineness modulus, moisture content as well as specific gravity tests were performed on all aggregates used. Furthermore, in order to achieve the required analytical depth for the materials being studied, x-ray diffraction and energy dispersive spectroscopy tests were conducted. As a means of conducting further trend analysis on the different experimental mixes, logarithmic regression models were developed. Through analysis of the output attained from the aforementioned strategies, this research study found that when cement was substituted by eggshell powder at a percentage of 5 % and simultaneously when coarse aggregate was also substituted by expanded polystyrene at a percentage of 5 %, all mixed with non-potable water, the compressive and flexural strength outcomes marginally differed from the strength outcomes of conventionally produced concrete. Furthermore, the substitution of stone by EPS at a percentage of 10 % when mixed with river water was comparable to the substitution of stone by EPS at a percentage of 10 % when mixed with potable water. The results showed that there was a difference of not more than 1.4 MPa and 0.3 MPa in compressive and flexural strength respectively amongst the averages obtained at each age tested. Study results show that the substitution of potable water by non-potable water reduced both the compressive and flexural strength of the concrete when the mix did not contain eggshell powder. However, when eggshell powder was included in the mix, the strength outcomes of the compressive and flexural strength of the concrete mix was comparable to that of conventionally produced concrete. There may be many reasons why it is important to not deviate from convention in the production of numerous products such as concrete; nevertheless, the value of experimentation as demonstrated in this research is that experimentation can give rise to a variety of innovations accompanied by a wealth of solutions to the environmental and socio-economic issues that the world is currently faced with.Item An investigation into the structural suitability of standard grade Expanded Polystyrene (EPS) as an innovative building material(2019-11) Mncwango, Bonke; Allopi, DhirenRapid urbanization has brought numerous economic, cultural and political development in South Africa; however, it has also led to some parts of the country turning into slums. The spread of slums is mainly driven by the lack of adequate housing provision by the Government. Although it has been twenty-five years since South Africa had its first democratic elections, millions of citizens still continue to live under squalid conditions as a result of lack of housing. The South African government cites numerous reasons for not being able to eradicate the housing backlog, including insufficient housing budget allocation as well as the worsening global economic climate. It is evident from the current housing backlogs that more building solutions that can reduce cost and construction time are needed. Further, new building materials should be explored in order to alleviate the environmental pressures that conventional building materials cause on the environment. This research investigates the properties of standard grade Expanded Polystyrene (EPS) as a potential contributor in low-cost housing provision. Currently the construction of EPS dome houses using modified EPS is only occurring outside of South Africa and it requires the possession of intricate moulding equipment. Existing suppliers require a minimum order, for instance, Japan Dome House Company supplies dome houses at a minimum order of three-hundred units. This research examines the potential of carving standard grade EPS into a form of dwelling using a hot-wire tool to re-create a model similar to a commercially produced EPS dome house. EPS components were assembled and left exposed to the elements since the main method of analyses of the live model was through exposure, particularly against rain and wind experienced within the jurisdiction of Pietermaritzburg, South Africa. Analyses of the live model was supplemented by testing of compression, flexural and thermal qualities of EPS under laboratory conditions. With wind speeds of thirty-nine km/hr and a rainfall intensity of twenty-eight mm, the model was found to still be in its original state of composure after six-months even without having been permanently anchored to the ground. Existing industry models such as Moladi, Khaya ReadyKit and Fischer Housing were examined to provide a standard of comparison for this investigation. This was done in order to distinguish how EPS dome houses differ to current existing alternative building technologies within the sector of low-cost housing. Observation of the model revealed that it is possible to successfully re-create an EPS dome house without complex moulding equipment. Some of the main findings from the laboratory analysis were that, contrary to expectations, thermo-gravimetric analyses of three different densities (fifteen kg/m3, twenty kg/m3 and thirty kg/m3) revealed that as the density of EPS increases, the maximum degradation value decreases. A study of the interaction of the polystyrene beads through microscopic analysis revealed that in higher EPS densities beads can rupture, leading to a compromise in both structural integrity and form. A water absorption test on EPS revealed that the percentage of water absorbed by EPS is similar to that absorbed by clay bricks over a 24-hour period, which makes the materials comparable in this regard. In terms of the outcomes of the study, the researcher has already published articles in three journals and two conference proceedings. This research will be of value to design professionals in alleviating the environmental impacts of commonly used conventional materials through the inclusion of EPS where low compressive loads are permissible.