https://ir.unisa.ac.za/handle/10500/2924 2026-06-28T17:34:24Z https://ir.unisa.ac.za/handle/10500/32667 The potential of epoxy coated chicken feathers as modified natural fiber in concrete Rikhotso, Mixo Asset This study assessed the viability of incorporating both untreated (UCF) and treated chicken feathers (TCF) into concrete to enhance sustainability in the construction industry. Five concrete mixes were tested, with Mix 4 (0.75% TCF) and Mix 5 (1.25% TCF) emerging as the most promising. These mixes showed improved workability and retained high compressive and tensile strength compared to the control. In contrast, the mix with 1% UCF exhibited significant reductions in mechanical and durability performance. Durability tests confirmed that TCF-enhanced concrete maintained resistance to oxygen permeability, water absorption, and chloride penetration, while also displaying reduced shrinkage. Overall, treated feathers proved to be a suitable partial replacement in non-structural concrete applications, offering both environmental and engineering benefits. Text and abstract in English 2025-06-01T00:00:00Z https://ir.unisa.ac.za/handle/10500/32631 Geotechnical analysis of dolomitic terrain to assess the probability of sinkhole formation : a case study of Centurion, South Africa Mavhetha, Lavhelesani Dolomitic terrain in the Gauteng Province of South Africa presents significant geotechnical challenges for urban development. This is primarily due to subsurface dissolution processes that create void networks susceptible to sinkhole formation and ground subsidence. This research study explores the case of Cornwall Hill in Centurion where numerous sinkhole incidents have caused infrastructure damage and imposed severe development constraints. A multi-method investigation approach was employed, combining gravity geophysical surveys, test pit excavations, rotary percussion boreholes, dynamic cone penetrometer tests, and laboratory analysis. Gravity surveys comprised 105 measurement stations on a 50 m × 50 m grid. Five test pits were excavated while four rotary percussion boreholes were drilled to depths between 10 and 25 m. Five dynamic cone penetrometer tests were also carried out on site and rotary percussion drilling was done to complement gravity surveys. Lastly, a comprehensive laboratory geotechnical analysis programme was done on field samples collected on site. Results revealed that the site is underlain by Malmani Subgroup dolomites overlain by a consistent three-layer stratigraphic sequence comprising colluvium, residual soil, and dolomite bedrock. The residual soils exhibited consistent classification as low plasticity clay with plasticity indices of 11 – 14% and a gravel-rich composition at 50 – 60%. However, the soils displayed significant spatial variability in thickness (0.70 – 2.70 m) and bearing capacity (152 – 320 kPa at 0.7 – 0.8 m depth). Rotary percussion drilling confirmed the presence of shallow competent dolomite beneath chert layers at 2 m depth and colluvium overlying interbedded chert and dolomite from 3 m depth. A cavity located within the peripheral low-density gravity zone and extending from 2 m to 13 m depth before competent material was also reached. Gravity survey results defined the subsurface density contrast, with high-density areas (covering 60% of the site) indicating shallow competent bedrock at 1.0–1.6 m depth and low-density areas (covering 40% of the site) indicating deep weathering profiles exceeding 2.7 m; the cavity intersected in BH01 directly correlates with low gravity in the peripheral zone. The site was described into Zone A (central D3 area of the site suitable for development with raft foundations at 600–900 mm depth) and Zone B (peripheral D4 area of the site unsuitable for development owing to the presence of a cavity, gravity lows indicating solution features, and high collapse potential) based on the results of integrated geophysical, intrusive, and laboratory investigation. The study meets the requirements of SANS 1936-2:2012 and proves the potential of integrated characterization of complex terrain, including the application of Rotary Percussion Drilling (RPD) as ground truth, for making informed decisions regarding development of difficult terrain such as this dolomitic environment, while providing valuable geotechnical data for the Centurion region. 2026-05-19T00:00:00Z https://ir.unisa.ac.za/handle/10500/32261 Reliability analysis of studded shear connectors in composite slabs subjected to shear loading Morudu, Kagiso Ntate This study investigated the reliability of stud connectors in composite slabs subjected to shear loading, focusing on the adequacy and efficiency of design provisions outlined in four major international codes: SANS 10162-4, EN 1994, AISC 360, and AS/NZS 2327:2017. The analysis evaluated the safety margins and conservatism inherent in these codes, using both the First Order Reliability Method (FORM) and Monte Carlo Simulation (MCS) to assess the probability of failure of stud connectors under various loading and material conditions. The study began by analysing model uncertainty, revealing significant differences in bias and variability among the design codes. The SANS 10162-4 model showed no bias and minimal variability, while AISC 360 demonstrated the largest bias and variability. EN 1994 and AS/NZS 2327:2017 displayed moderate levels of conservatism. Reliability indices were computed for each design code, with results indicating that all models provided sufficient safety margins, though EN 1994 and AISC 360 exhibited excessive conservatism that may lead to overdesign. A sensitivity analysis based on FORM identified variable actions as the most critical factor affecting reliability, followed by stud diameter. The implications of these findings were used to propose adjustments to partial safety and reduction factors to optimize design efficiency without compromising safety. For instance, a reduction in the partial safety factor from 1.25 to 1.1 for EN 1994:2005, and an increase in the partial reduction factor for AISC 360 from 0.65 to 0.80, were recommended. The study concludes that while the current design standards provide adequate safety, there is significant potential for optimization, particularly in reducing conservatism in certain models. Future research is recommended to refine design models, account for more complex loading conditions, and explore probabilistic methods to further enhance the reliability and efficiency of stud connector designs. Limitations of the study include the use of simplified load conditions and assumptions about material properties, as well as the exclusion of long-term effects such as creep and shrinkage. In summary, this study evaluates the reliability performance of existing stud-connector design models and develops calibrated resistance factors that enhance their consistency with target reliability levels, providing evidence that can inform future improvements to design provisions while maintaining adequate safety margins. 2025-09-01T00:00:00Z https://ir.unisa.ac.za/handle/10500/32122 Biodegradation of environmental significant inorganics using aerobic bacteria found in Blesbokspruit Wetland, South Africa Kgabile, Mpho Gift The Blesbokspruit wetland is known to be one of the imperative wetlands in Republic of South Africa (RSA), located in region of Ekurhuleni, Gauteng Province. A continuous discharge towards the Blesbokspruit wetland from effluents coming from the nearby Grootvlei mine, paper production company (South African Pulp and Paper Industries) and other anthropogenic activities accompanied with environmental impurities which include cyanide-residues has been witnessed within the wetland. Cyanide compounds depict distinct characteristics depending on chemical bindings with other elements which determines their severity and stability of the compound. Cyanides are either classified as either organic or inorganic cyanides and they are regarded as environmental significant contaminants. Biodegradation processes have proved to be an ideal tool to degrade environmental significant contaminants due to its cost effectiveness, eco-friendly and durability. The environmental significant inorganic placed under study is thiocyanate and its biodegradability using microorganisms isolated from soil, water and sludge within Blesbokspruit wetland. Among the most problematic inorganics found in wetlands are cyanides, particularly thiocyanate, which are toxicophores due to their cyanide content. Studies have shown that cyanides are present in effluents channelled by mining industries, which results in the deterioration of the Blesbokspruit wetland. Microorganisms were isolated and identified using universal primers 16S-27F and 16S-1492R, targeting 16S rDNA sequence. Indicator plate technique was applied in order to detect microorganisms with thiocyanate biodegradation capabilities, where phenol red aided as an indicator to distinguish microorganisms that can degrade thiocyanate by observing a colour change from red to pink. Later, thiocyanate degrading isolates and mixed culture were inoculated in minimal media without addition of a carbon or nitrogen source and 1/10th minimal medium containing a 24-hour starved culture was further inoculated in batch conical flasks containing minimal media with thiocyanate (SCN) either 150 mg SCN-/L or 250 mg SCN-/L. The sampling intervals were done every 24 hour-interval for a duration of 5 days, whereby the absorbance of microbial growth was measured at 600 nm and ammonium-nitrogen was measured with use of Merck Spectroquant Pharo 300. The results have shown that only few bacterial isolates were more effective compared to the bacterial consortium with regards to biodegrading thiocyanate, whereas the highest biological thiocyanate removal efficiency achieved in this study was 97.44 % and 95.71 % under 150 mg SCN-/L and 250 mg SCN-/L by Exiguobacterium sp., respectively. Most of bacterial isolates gave less biological thiocyanate removal efficiency as compared to bacterial consortium which was dominantly comprised by Pseudomonas sp. It was concluded that aerobic bacteria obtained at the Blesbokspruit wetland were capable of biodegrading thiocyanate which is deemed as an environmental significant inorganic. The greater concentration amounts of thiocyanate, most bacteria seemed to be susceptible to exposure, although few bacteria exhibited some form of resistance to some extent. Most of these bacteria were able nitrify the available ammonium-nitrogen. 2022-12-21T00:00:00Z