Faculty of 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 Life cycle assessment of the production of cement : a South African case study(2021-12-01) Olagunju, Busola Dorcas; Olanrewaju, Oludolapo AkanniThe relentless ongoing pursuit of innovation, development, urbanization and immigration for a better quality of life has impacted the natural environment. Also, the various consequences of continuous industrial activities are seen in the departure from what is supposed to be the norms of nature and an ideal environment free of toxicity, pollution and unquantifiable instantaneous changes. One of these is variation in temperature experienced in recent times as against what it was about 2000 years ago before the industrial revolution. A world with an increasing population requires infrastructure to support this growth. The construction industry is able to support this growth by building necessary structures that will accommodate environmental sustainability. However, the construction industry is responsible for several environmental impacts as a result of various activities. Concrete is one of the major base materials used in the construction industry and cement is an essential ingredient in concrete production. Several environmental impacts ranging from high greenhouse gas (GHG) levels to high energy consumption (fossil fuel and electricity) to high resource usage are associated with cement production. Quantifying these impacts is a major roadmap to reducing them. In this study an analysis of the production model of South African cement plants was carried out so as to quantify its impacts, and know how they consequently affect the lives of South Africans, her resources as well as the ecosystem; so that proper mitigation strategies can be recommended. The study carried out a Life cycle assessment (LCA) of cement using both the midpoint and endpoint approaches of the LCIA. LCA is a tool used to analyze the environmental impact of a process or product from start to finish. This study carried out a cradle-to-gate analysis of 1kg of cement produced in a typical South African plant using data from the Ecoinvent database and SimaPro 9.1.1 software. The result showed that for every 1kg of cement produced, O.993 CO2 eq, was emitted into the atmosphere; 98.8% was actual CO2 emission and its resultant effect was global warming which causes changes in climatic conditions. Also, 1.6kg of 1,4-Dichlorobenzene (1,4-DCB) eq was emitted into the air and water, which caused high toxicity in these media and for every 1kg of cement produced, 0.139kg of oil eq was produced and its effect was seen in fossil resources scarcity. Of this value, 0.125kg was from the burning of coal In both approaches, the result was further analyzed with respect to five major production processes: (1) Clinker production (2) Raw material consumption (3) Electricity usage (4) Fuel consumption and (5) Transportation. The results showed that the clinker production stage contributed 76.3% to global warming; and raw material consumption contributed 95.9%, 99.9%, 90.7%, and 77.9% to ionization radiation, mineral scarcity, fossil resource scarcity and terrestrial ecotoxicity, respectively. Fuel consumption contributed 98.6%, 96.3%, 85.7% and 76.9% to freshwater eutrophication, marine eutrophication, human carcinogenic toxicity, and human non-carcinogenic toxicity, respectively. Electricity usage contributed 65.8% and 64.8% to stratospheric ozone depletion and fine particulate matter formation, respectively. Though South Africa relies on the importation of clinker and cement, in the endpoint approach an estimation was carried out based on the annual requirement of cement in South Africa without importing either commodity. The result showed that 55 404 was the potential number of human lives that could be endangered annually; 133 species had the potential to be endangered annually, and the effect of a potential scarcity of resources caused total a marginal price increase of R6.2 billion due to these damages. The results of the analysis are in line with previously published literature but with slight variations. In conclusion, the study prescribed mitigation and adaptation strategies to counter these environmental impacts.