Masters Degrees (Civil Engineering)

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Browsing Masters Degrees (Civil Engineering) by browse.metadata.advisor "Babafemi, Adewumi John"

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    3D printing of eco-friendly concrete incorporating recycled plastic waste (RESIN8) as fine aggregate
    (Stellenbosch : Stellenbosch University, 2022-12) Oosthuizen, Jandré Daniel; Babafemi, Adewumi John; Walls, Richard Shaun; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
    ENGLISH BSTRACTS: Plastic waste is a massive environmental issue worldwide which cannot be solved in a simple manner. Sand being a natural resource is limited in nature in contrast to the abundance of waste plastics in our environment. This study, therefore, investigates the suitability of creating an eco-friendly 3D printable concrete where recycled plastic waste, in the form of Resin8, is incorporated by replacing different percentages of fine aggregates. Replacement values of 5%, 10% and 15% of natural sand by volume are investigated, which are further characterized by varying Resin8 particle sizes. Particle sizes of Resin8 included are sub-5 mm, sub-1 mm and a combination of the two by mixing them by equal proportions (50/50). The concrete incorporating recycled plastic waste (Resin8) was compared to, and tested against a reference concrete mix which is the standard 3DPC mix at Stellenbosch University. Samples of each concrete mix were also mould cast into 160 x 40 x 40 mm prisms from the same concrete mix that were used for printing to investigate the effect the printing process had on the mechanical properties of the concrete. The rheology, slump flow (workability), buildability, air content and density are some of the fresh properties that were investigated. The mechanical properties of the different concrete mixes were investigated by means of flexural (4-point bending) and compression tests. Due to the anisotropic nature of 3DPC, the printed samples were tested in two different directions; D1 and D3. Porosity analysis by means of Computed Tomography (CT) scans were done on printed and cast samples of the reference mix as well as all sub-1 mm Resin8 printed samples to compare and investigate the effect of Resin8 on the microstructure of the printed concrete. Scanning Electron Microscopy (SEM) analysis was conducted on sub-5 mm and sub-1 mm Resin8 particles used in this study, as well as on the 3D printed samples of the reference mix and all replacement percentages of the combination Resin8 mixes after 28 days. All mixes containing Resin8 performed adequately for use in 3DPC based on characterisation of its fresh properties. It was observed that mixes containing Resin8 were more flowable, which has been validated by an increase in slump flow value when compared to the reference mix, while the buildability was negatively affected by the increased flowability. A lower density was obtained as the percentage of Resin8 replacement increased as expected due to the lower relative density of Resin8 compared to sand. Both the flexural and compressive strength decreased as the Resin8 replacement increased. However, an increase in interlayer bond strength was observed in all Resin8 mixes compared to the reference mix, which could possibly be as a result of excess pore water at the interlayer region due to the hydrophobic nature of plastics. The printing process had little effect on the performance of the 3DPC mixes based on similar flexural and compressive strength results achieved for orientation D3 and the mould cast samples, while orientation D1 yielded the best results. Considering the results obtained in this research, the addition of Resin8 into 3D printable concrete is a feasible option and could potentially lead to great reductions of waste plastics in our natural environment even for low replacement volumes.
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    Alkali-resistant glass textile reinforcement of 3D printed concrete
    (Stellenbosch : Stellenbosch University, 2022, 2022-12) Janse van Rensburg, Johannes Jacobus; Combrinck, Riaan; Babafemi, Adewumi John; Civil Engineering; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
    ENGLISH ABSTRACT: Additive manufacturing such as 3D concrete printing (3DCP), has recently gained significant attention due to its numerous benefits. However, 3DCP still has significant challenges to overcome before it can be fully adopted as a feasible alternative to conventional construction methods. The reinforcement of 3D printed concrete elements has proven to be challenging and needs to be addressed. Moreover, there are multiple aspects to this challenge that need to be taken into account, such as the lack of clear space above the filament layer being printed, difficulty in installing the reinforcement in different directions as well as integrating the reinforcement into the printing process. Various strategies have been studied in order to address these challenges, with different materials used as reinforcement before, during or after printing. However, before reinforcement can be applied, the behaviour of the consequent composite materials must first be studied. This study, therefore, investigates the flexural performance and behaviour of two different alkaliresistant (AR) glass textile materials as reinforcement to determine whether it is a feasible solution. During this study, two different methods of printing and applications of the textiles are considered, one where the elements are printed vertically and the textiles are pre-installed, and one where the elements are printed horizontally and the textiles are installed during the printing process. The textiles are applied in two different locations, one at the middle of the depth of the sample and one lower down. Samples are extracted from these printed elements and tested in flexure by conducting fourpoint bending tests 28 days after printing. After conducting these tests, the crack sequence and failure mechanisms of the variations are investigated. Furthermore, an optical microscope is used to gather more information regarding the performance and failure of the various samples. The results show that there is a significant increase in the flexural performance of the samples reinforced with an AR glass Textile A. Textile A is fully impregnated with epoxy resin, with high tensile strength, stiffness, and large cross-section area. Additionally, the application of this textile promotes deflection hardening structural behaviour. However, in contrast, there is a significant increase in ductility with no increase in flexural strength for the samples reinforced with an AR glass Textile B. Textile B is coated with styrene butadiene, with high tensile strength but a small section area. The results further indicate that the samples reinforced lower in the sample experience higher flexural strength with lower ductility and more variability in behaviour. During testing, it is also discovered that voids form underneath Textile A when applied to horizontally printed samples (between the interlayers), and that these voids influence the performance of the samples. The voids further influence the failure mode as well as the cracking sequence. Investigation of the failure of the samples reinforced with Textile A show two failure mechanisms occurring, namely, delamination and shear. Delamination always occurs when the textile is applied in the middle of the depth of the samples, but shear only occasionally occurs for the variation where the textile is applied lower in the sample. Additionally, telescopic failure is detected for Textile B. It is concluded that for both the textiles, the best performance, behaviour and repeatability are observed when the elements are vertically printed, and the textiles are placed in the middle of the depth of the sample. Among others, it is recommended to apply different variations of textiles, use different application techniques (such as retrofitting) and to explore the micro mechanical behaviour of 3DPC elements reinforced with textiles in future studies.
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    Behaviour of masonry systems incorporating waste plastic subjected to fire
    (Stellenbosch : Stellenbosch University, 2020-04) Botha, Ayden Dennis; Walls, Richard Shaun; Babafemi, Adewumi John; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
    ENGLISH ABSTRACT: Plastic waste within the built environment is a global concern, with proportions of waste plastic produced in municipal solid waste being more than 10% by the beginning of the millennium. Within the engineering community, the use of construction materials implementing waste plastics has been a recent development that aims to minimise the effect of plastic waste on the environment. One major concern, however, is that addition of plastics has an unknown impact on the fire response and behaviour of recycled construction products. All structures are required to have a fire rating to quantify the resistance of the structure to a fire event. The unknown response of recycled construction materials to fire has resulted in the investigation of several recycled construction systems within this thesis. Systems that were analysed include Ecobricks (a building block made of a plastic bottle that is filled with plastic infill material), adobe bricks (building units made from natural in-situ soils) and RESIN8 bricks (concrete masonry units with added plastic aggregate replacement). The exposure of each of these systems to a heat source representing a small fire allowed their respective response to fire to be examined, both qualitatively and quantitively, and for observed behaviour to be captured. The adaptation of a newly developed system for fire response testing (Heat Transfer Rate Inducing System or H-TRIS) was employed for the experimentation carried out in this thesis. The system used involved the use of electric radiant panels for means of heating experiments (coined as the eH-TRIS). Samples were subjected to constant heat fluxes of up to 35 kW/m² imparted purely by means of radiative heat transfer, without the effect of the convective zone heating the sample. A qualitative assessment of the behaviour of exposed Ecobricks with the use of video and photographic data was performed, as well as quantitative thermal assessment of the associated adobe protection system. A quantitative analysis of the RESIN8 samples was carried out to determine total mass losses, release of energy as well as total heat release rates for samples of increasing replacement plastic content. In addition, the pre- and post-fire compressive strengths of the RESIN8 samples were determined to quantify the effect of fire on the capacity of brick strength. The use of exposed Ecobricks was found to lead to undesirable fire behaviour, including the presence of flaming droplets, high smoke production and sustained burning immediately after ignition. A significant improvement was observed with the use of adobe, with minimal effects of heat transfer impacting on the system. The replacement content of the RESIN8 samples influenced both smoke production and heat transfer, with high volumes of smoke observed for the highest replacement group. Capacity of the RESIN8 units was also found to drop up to 34.7% of original compressive strength, with heat releases ranging from 291 to 3075 kW with an increase in RESIN8 replacement. The research in this paper aims to act as a spearhead into the topic of these systems, as further research will be required into the many other facets (and additional construction materials) that remain.
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    Fire behaviour of plastic bottle ecobricks as an infill building material
    (Stellenbosch : Stellenbosch University, 2022-04) Sander, Zara Rose; Walls, Richard Shaun; Babafemi, Adewumi John; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
    ENGLISH ABSTRACT: A global increased awareness of plastic pollution, and the consequences of not addressing said problem, has led to increased interest and adoption of ecobricks as a building material. Ecobricks consist of any size plastic beverage bottle, densely filled with dry, non-recyclable plastic. As a result, places such as schools, shops and crèches around the world are collecting them and using them as an infill material in the construction of private and municipal projects. Construction projects incorporating ecobricks involve placing the plastic bricks inside a timber or reinforced concrete frame. The frame is sometimes covered with steel mesh (“chicken wire”) and plastered with various plaster-mixes. Ecobrick structures have gained popularity, with over 200 schools in Guatemala having been built using ecobricks. With plastics being highly flammable, it is important that the construction and fire engineering industries understand how they may perform when exposed to fire. The problem this thesis aims to answer is: how do ecobrick walls behave when exposed to fire, and how can they be built to ensure that they are safe? As construction using ecobricks is relatively new, minimal research has been done regarding fire safety. Two of the most common methods for constructing homes out of ecobricks were identified. One consists of laying ecobricks horizontally between cob (a clay-straw-sand-mortar mix). The alternative was to stack them vertically and encase them with a mesh and plaster. In this work, various plaster systems were tested, including, (a) traditional cement-sand mortar, (b) lime mortar, and (c) cob. This thesis investigates the placement of bottles, the application of plaster, and the use of mesh layers in relation to the thermal performance of ecobricks in a standard fire test. Six wall samples were built to represent the two different construction methods and three different plasters. The samples were tested in a large-scale furnace where the temperatures were measured through the cross-section of each wall. The temperatures were then compared against 2D thermal modelled wall samples to understand the thermal behaviour of the plaster and ecobricks. The plaster of each wall sample proved to be critical in the fire behaviour of the samples. The most favourable ecobrick and plaster combination, a cob plaster of 40 mm on the horizontal ecobrick wall sample, was able to achieve a one-hour fire rating, where the ecobricks did not melt or ignite. Samples tested with a vertical ecobrick and cement mortar experienced severe flaming and failed after 56 minutes, with some samples failing significantly faster. The lime plaster delaminated early on resulting in rapid failure. Preliminary guidelines for ensuring suitable fire behaviour are presented.
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    Mechanical properties of eco-friendly one-part metakaolin-based geopolymer concrete with Recycled Glass and Plastic (RESIN8) aggregates
    (Stellenbosch : Stellenbosch University, 2023-11) Ajayi, Babatunde Luke; Babafemi, Adewumi John; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
    ENGLISH ABSTRACT: The high demand for concrete in the construction industry is directly proportional to the demand for Portland cement (PC), which is the binding agent in concrete. However, PC production leads to the emission of its equivalent amount of carbon dioxide (CO2), resulting in global warming. Consequently, a one-part "just add water" geopolymer binder is developed, which is a potential sustainable binder that could substitute PC. Therefore, this study investigates and reports the mechanical performance, microstructural properties, and cost analysis of a one-part metakaolin-based geopolymer concrete (GPC) produced with anhydrous sodium silicate, sodium hydroxide, and calcium hydroxide as alkali reagents. The GPC materials were pretreated and investigated to assess their physical properties (such as water absorption, particle gradation, specific gravity, and moisture content of the aggregates) and the chemical composition and morphology of the precursors. The optimum GPC mix design was obtained using the Taguchi experimental design approach, and the materials were dry-mixed before water was added. Further, the natural sand was substituted by fine waste aggregate (FWG) and RESIN8 (recycled plastic waste containing Resins 1–7), respectively, at a 5% and 10% replacement level. The influence of the recycled aggregates on the fresh and hardened properties of the composite was investigated and reported. Furthermore, the effects of different curing methods, such as climate-controlled curing (CC), water-curing (WC), and ambient-curing (AC) conditions, were investigated on the compressive strength. The samples tested for splitting tensile and flexural strength were subjected to AC conditions. Adding 5% and 10% of FWG and RESIN8 as fine aggregate in concrete enhances its workability. However, the compressive strength of samples with 5% and 10% RESIN8 is reduced by 15.1% and 19% for CC, 15.7% and 24.1% for AC, and 14.7% and 22% for WC, respectively, compared to their respective control GPC samples after 28 days of curing. On the other hand, the addition of 5% FWG improved the performance of the matrices by 8.9%, 3.5%, and 5.3% for CC, AC, and WC, respectively. After 28 days of curing, the strength of CC sample was increased by 13.6% due to the addition of 10% FWG. In contrast, the strength of AC and WC samples decreased by 0.7% and 1.7%, respectively, when compared to the control GPC samples. The compressive strength of AC samples shows a 10.9% improvement, whereas WC samples show a 16.3% improvement compared to the 28-day CC GPC samples. Further, the compressive strength of CC GPC declined after 28 days of curing; hence, the choice of curing condition greatly influences the performance of GPC. The enhanced strength of the AC and WC samples can be attributed to the presence of water within the concrete matrix, which allows for a complete geopolymerisation reaction. In contrast, the CC sample only underwent hydration due to the consistent curing temperature of 24 °C. The inclusion of 5% and 10% RESIN8 led to a 60.6% and 78% reduction, respectively, in the elastic modulus (E-mod) of GPC, while 5% and 10% FWG inclusion led to a 21.2% and 30.3% reduction in the E-mod of 28-day AC GPC, respectively. Using 5% and 10% FWG reduced the cost of GPC by 0.13% and 0.27%, respectively, while 5% and 10% RESIN8 increased the cost by 0.07% and 0.13%, respectively. The increased cost of RESIN8 containing GPC is due to the high cost of producing RESIN8. Conclusively, structural GPC is obtained, and 5% RESIN8 content and up to 10% FWG content have the potential to substitute natural sand in an environmentally friendly one-part metakaolin-based structural GPC. In contrast, 10% RESIN8 could be used for a non-structural concrete component. The use of RESIN8 and FWG in GPC possesses economic benefits and is a viable solution to environmental pollution, protection of aquatic lives and preservation of natural aggregates.