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Research Publications (Engineering and Built Environment)

Permanent URI for this collectionhttp://ir-dev.dut.ac.za/handle/10321/215

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Start date: 2010Has files: No

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    Experimental investigations on the effect of concrete quality, exposure conditions and duration of initial moist curing on carbonation rate in concretes exposed to urban, inland environment
    (Elsevier, 2020-02-12) Otieno, Mike; Ikotun, Jacob; Ballim, Yunus
    This paper reports an investigation on the influence of inland exposure conditions, concrete quality and cover depth on carbonation-induced corrosion initiation of steel in concretes exposed to urban, inland environment. 100 mm concrete cube specimens of were prepared using five types of binder namely plain Portland cement (CEM I 52.5 N, PC), 70/30 PC/FA (fly ash), 50/50 PC/BS (blast furnace slag), 90/10 PC/SF (silica fume) and 60/30/10 PC/BS/SF at three w/b ratios of 0.40, 0.60 and 0.95. For all the concretes, two companion sets of specimens were cast and cured for 7 and 28 days before being exposed to natural indoor, outdoor-sheltered and outdoor-unsheltered environments. Concrete quality was characterized using water sorptivity and oxygen permeability. Carbonation depths were measured at 6-month intervals up to 2 years. The results show that as the quality of the concrete increases the rate of carbonation rate decreases. The results also show that carbonation rate is more sensitive to concrete quality (binder type and w/b ratio) than duration of curing. The indoor-exposed specimens exhibited higher carbonation rates than the corresponding outdoor-exposed concretes. Blended cement concretes showed higher carbonation rate than to the plain PC concretes. An empirical carbonation rate prediction model incorporating both gas permeability and water sorptivity as input parameters is proposed.
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    The effect of treatment on kenaf fiber using green approach and their reinforced epoxy composites
    (Elsevier, 2016) Kotharangannagari, Venkata Krishna; Kanny, Krishnan
    In this study we show the novel treatment (surface modification) of kenaf fiber using amino acids and the studies of kenaf fiber reinforced epoxy composites. The kenaf fiber was treated at room temperature for 24 h, using two amino acids namely glutamic acid (acid) and lysine (base). Thermogravimetric analysis (TGA) of the treated kenaf fiber (glutamic acid treated and lysine treated) showed more weight loss than compared to untreated fiber. The tensile studies of the composites suggested improved me-chanical properties in both the cases, glutamic acid treated and lysine treated kenaf fiber than compared to untreated samples. Dynamic mechanical analysis (DMA) of the composites suggested that the storage modulus, loss modulus and tand were most influenced by the chemical treatment. The morphological studies of the kenaf fibers before and after treatment were examined using scanning electron microscopy (SEM) and revealed that the chemical treatment for 24 h, removed any impurity from thefibers surface. In addition, morphological studies of fractured mechanical testing composite samples using SEM were performed to understand the de-bonding of fiber/matrix adhesion. The results, confirmed that the lysine treatment is more effective than the glutamic acid treatment on kenaf fibers.
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    Biodegradable hybrid nanocomposites of starch/lysine and ZnO nanoparticles with shape memory properties
    (Elsevier, 2016) Kotharangannagari, Venkata Krishna; Kanny, Krishnan
    In food packing applications; the research works have been focused on the development of biodegradable pack-ing materials by using biopolymers such as starch, carrageenan, agar, and gelatine to replace with petroleum-based non-biodegradable polymers. In this present work we studied novel synthesis of biodegradable hybrid nanocomposites using starch, amino acid (lysine), polypropylene glycol (PPG) and ZnO nanoparticles (NPs) and their shape memory properties. A series of hybrid nanocomposites were prepared by solution casting meth-od, with various ZnO nanoparticles content such as 0 wt%, 1 wt%, 3 wt% and 5 wt% by keeping peptide content constant and varying the ratio between starch and ZnO nanoparticles content. The thermogravimetric analysis (TGA) of the hybrid nanocomposites suggested increased thermal stability with increasing ZnO nanoparticles content. The solubility of the hybrid nanocomposites in H2O is decreased with increasing ZnO nanoparticles con-tent. The moisture content in the hybrid nanocomposites is decreased with increasing ZnO nanoparticles content. The mechanical properties of the materials were increased with increasing ZnO nanoparticle content. Further-more, the hybrid nanocomposites showed a shape memory properties by placing the sample at room tempera-ture and then at 55 °C. The morphology of the hybrid nanocomposites was revealed using scanning electron microscopy (SEM). We believe that these biodegradable hybrid nanocomposite films can be useful in food pack-ing applications.
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    Barrier and biodegradable properties of corn starch-derived biopolymer film filled with nanoclay fillers
    (SAGE Publications, 2016-12-18) Mohan, T. P.; Devchand, Kay; Kanny, Krishnan
    The objective of this work is to study the effect of nanoclay fillers on the biodegradation and barrier properties of corn starch polymer-based biofilm. Starch derived from corn plant source was used to prepare a biofilm by plasticization method. The barrier properties, namely, water absorption, moisture permeation, oxygen permeation and swelling of unfilled and nanoclay-filled corn starch biofilms were examined. The results indicate: ∼22% reduced water absorption, 40% reduced moisture uptake, 30% reduced oxygen permeation and 31% reduced swelling for 2–3 wt.% nanoclay-filled biofilm, when compared with unfilled biopolymer. The biodegradation result of unfilled and nanoclay-filled film series indicates that the nanoclay addition delays the biodegradation and is a function of nanoclay content in the film. The tensile, dynamic mechanical analysis and biodegradable studies were conducted on the biopolymers before and after water absorption, and the result shows that the nanoclay-filled biopolymer increased these properties when compared with unfilled biopolymer even after water absorption and is dependent on the nanocomposite structure and morphology as examined by X-ray diffraction and transmission electron microscopy analysis.
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    Treatment of industrial mineral oil wastewater – effects of coagulant type and dosage
    (IWA Publishing, 2017) Tetteh, E. Kweinor; Rathilal, Sudesh; Robinson, Kate
    The use of coagulants is essential in the diverse disciplines of conventional water and wastewater treatment. This work aimed to select an economic and effective coagulant, to minimize the cost of treatment and the oil droplet content of the water, thus enhancing the efficiency of a local South African oil refinery effluent plant recovering water and oil for reuse by treating the industrial mineral oil wastewater. A standard dissolved air flotation jar test preceded evaluation of four coagulants, viz. aluminum sulfate (Alum), aluminum chloride, ferric sulfate and ferric chloride. Chemical oxygen demand, soap oil and grease, total suspended solids and turbidity were determined as water quality parameters to check coagulant efficiency. Removal of over 70% was achieved for each parameter. The results obtained at pH 5 and coagulant dose of 50 mg/L showed that alum was the best pretreatment coagulant for destabilizing and minimizing oil droplets in water, due to its trivalent cationic nature. It was also economically viable.
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    Development and evaluation of a small scale water disinfection system
    (IWA Publishing, 2016-07-08) Alfa, Dorcas; Rathilal, Sudesh; Pikwa, Kumnandi; Chollom, Martha Noro; Pillay, Visvanathan Lingamurti
    Provision of microbiologically safe drinking water for people living in the rural areas of developing countries remains a major challenge to date. A simple gravity-driven membrane point of use system was developed based on woven fabric microfiltration (WFMF) membranes. The WFMF is a loose type of membrane (0.45 μm). However, complete disinfection is not achieved with the WFMF, hence it was incorporated with two disinfectants. This study aimed to combine the WFMF with two disinfectants (Water guard and bromochlor tablets) to bring the water to the accepted quality for drinking. Four different types of water were sourced, considering two factors; E. coli and turbidity content. The WFMF demonstrated excellent filtration performance by producing permeates with turbidity less than 1 NTU for feed turbidity ranging between 10 and 200 NTU. There was 95–99.8% E. coli removal for raw feeds with influent E. coli ranging between 500 and 44,500 CFU/100 mL. Total disinfection was achieved with both disinfectants, however, the effectiveness of the chemical disinfectants in E. coli removal was affected by the quality of water to be disinfected. The study showed that turbidity plays a major role in disinfection performances by increasing chlorine demand on water sources with high turbidity levels.
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    Evaluation of flux stabilisation using Bio-UF membrane filter on KZN Rivers, South Africa
    (Techno-Press, 2016) Thoola, Maipato Immaculate; Rathilal, Sudesh; Pillay, Lingham V.
    South Africa recognises piped water as the main source of safe drinking water supply. Remote areas do not have access to this resource and they rely solely on surface water for survival, which exposes them to waterborne diseases. Interim point of use solutions are not practiced due to their laboriousness and alteration of the taste. Bio-ultra low pressure driven membrane system has been noted to be able to produce stable fluxes after one week of operation; however, there is limited literature on South African waters. This study was conducted on three rivers namely; Umgeni, Umbilo and Tugela. Three laboratory systems were setup to evaluate the performance of the technology in terms of producing stable fluxes and water that is compliant with the WHO 2008 drinking water guideline with regards to turbidity, total coliforms and E.coli. The obtained flux rate trends were similar to those noted in literature where they are referred to as stable fluxes. However, when further comparing the obtained fluxes to the normal dead-end filtration curve, it was noted that both the Umbilo and Tugela Rivers responded similarly to a normal dead-end filtration curve. The Umgeni River was noted to produce flux rates which were higher than those obtainable under normal dead-end. It can be concluded that there was no stabilisation of flux noted. However, feed water with low E.coli and turbidity concentrations enhances the flux rates. The technology was noted to produce water of less than 1 NTU and 100% removal efficiency for E.coli and total coliforms.
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    Fault investigation methods on power transmission line : a comparative study
    (IEEE, 2016) Subramani, C.; Jimoh, A. A.; Sudheesh, M.; Davidson, Innocent E.
    In this paper, the authors have carried out fault investigation in Power Transmission Line using three different techniques: Simple impedance method, Travelling wave method and Wavelet Multi-Resolution Technique. Different realistic fault cases at different locations have been done but L-L fault is considered for this investigation. A two terminal 400kV transmission line fed by two generators model is simulated with MATLAB for all the three different techniques. The authors believe that the technique employed here is generally applicable to determine fault in any multi terminal transmission line.
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    Modeling and control of voltage source converters for grid integration of a wind turbine system
    (IEEE, 2016) Hamatwi, E.; Davidson, Innocent E.; Gitau, M. N.; Adam, G. P.
    Wind energy is one of the most promising renewable energy sources for generating electricity due to its cost competitiveness when compared to the conventional energy sources (fossil fuels). Wind farms are usually located far from the loads for minimal disturbances and optimal power generation. High Voltage Direct Current (HVDC) transmission is the preferred bulk power transmission system over long distances due to the minimal transmission losses, low costs and reduced environmental impacts. In this research investigation, a 690V, 2MW wind turbine equipped with a PMSG is modelled to be integrated into a local 33kV AC grid via a 2-level VSC-based HVDC transmission system. Three control schemes are implemented on the proposed system: a blade-pitch-angle controller applied on the wind turbine model, a field-oriented rotor speed controller applied on the rectifier for maximum power extraction, and a vector-oriented direct-current-link voltage controller applied on the grid-side inverter to keep the DC-link voltage constant and to ensure unity power factor. The proposed subsystems are implemented in MATLAB/Simulink and simulations are carried out to analyze the overall system’s performance.
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    Analysis of current Pulses in HeLa-Cell Permeabilization due to high voltage DC corona discharge
    (IEEE, 2016-09) Chetty, Nevendra K.; Chonco, Louis; Ijumba, Nelson M.; Chetty, Leon; Govender, Thavendran; Parboosing, Raveen; Davidson, Innocent Ewaen
    Corona discharges are commonly utilized for numerous practical applications, including bio-technological ones. The corona induced transfer of normally impermeant molecules into the interior of biological cells has recently been successfully demonstrated. The exact nature of the interaction of the corona discharge with a cell membrane is still unknown, how-ever, previous studies have suggested that it is either the electric fields produced by ions or the chemical interaction of the reactive species that result in the disruption of the cell membrane. This disruption of the cell membrane allows molecules to permeate into the cell. Corona discharge current constitutes a series of pulses, and it is during these pulses that the ions and reactive species are produced. It stands to reason, therefore, that the nature of these corona pulses would have an influence on the level of cell permeabilization and cell destruction. In this investigation, an analysis of the width, rise-time, characteristic frequencies, magnitude, and repetition rate of the nanosecond pulses was carried out in order to establish the relationship between these factors and the levels of cell membrane permeabilization and cell destruction. Results obtained are presented and discussed.