Faculty of Engineering and the Built Environment (ETDs)

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Analysing the progress of skills development necessary for mineral beneficiation in the gold mining industry: a case study of harmony gold’s Moab khotsong mine
(University of the Witwatersrand, Johannesburg, 2024) Nengwenani, Shumani Maemu; Mtegha, H.
The mining industry of South Africa is a cornerstone of the country’s economy, having contributed over 8% to the national gross domestic product in 2022. The mining industry has been responsible for major economic growth and job creation due to its mineral resource abundance. However, the socio-economic impact of this industry on communities has fallen short of expectations. The objective of the South African beneficiation strategy is to transform the country’s mineral wealth into competitive economic advantage through the promotion of economic diversification, industrialization, and job creation. The aim of this research is to determine progress made by the mining sector in skills training and development necessary for local mineral beneficiation, particularly in the gold mining industry. This is training provided through the achievement of formal qualifications such as a National Certificate in Jewellery Manufacturing, a Diploma in Jewellery design and Manufacture, as well as through the accumulation of skills such as jewellery processing, wax carving for jewellery, die stamping for jewellery, industrial design for jewellery, and jewellery evaluation. The reaserch also includes a critical reviews the company’s training initiatives within the context of the beneficiation skills pipeline, the National Skills Development Strategy, and the sector skills plan, which are all key elements of the National Growth Plan and the relevant Sector and Training Authorities. Harmony Gold company has shown commitment to socio-economic objectives through the implementation of numerous beneficiation projects, such as the Musuku Beneficiation Systems, the Harmony Jewellery School, the Oro-Maska Project, and the SARM project. While these initiations did not have long-term success, they indicate the company’s willingness to play a role in promoting skills transfer and in mineral beneficiation. The short-term success of these initiatives also highlights the complexities involved, underlining the need for proper planning, proper resource allocation, as well as the need for constant and consistent stakeholder engagement. A significant finding of this research is the identification of a skills gap, especially in areas crucial for mineral beneficiation. Despite existing efforts and policy frameworks like the Skills Development Act 97 of 1998, the remains a need for more targeted training and skills development programs. The existing skills gap must be addressed to maximize the mining sector’s contribution to national development objectives.
Evaluation of the Performance of the BlastLogic Software in Predicting Blasting Fragmentation Distribution in Surface Mines
(University of the Witwatersrand, Johannesburg, 2024) Munkombwe, Milton; Uludag, Erhan
Surface mining is a crucial aspect of the mining industry, and one of the most significant factors that affect profitability and efficiency in mining operations is fragmentation. The traditional approach to fragmentation in surface mines involves the use of explosives, which generates a particular fragmentation profile that may not always be targeted size. The objective of this study was to evaluate the performance of the BlastLogic software in predicting fragmentation distribution in surface mines. This was in comparison with Swebrec, Kuz-Ram and Split-Desktop fragmentation results. Drill pattern designs are created (burden, spacing and hole position) in other design parameter software e.g., Maptek Vulcan, and Micro-station. These patterns are optimised in the BlastLogic software package. It uses advanced algorithms and models to simulate and predict the effects of different blasting parameters on fragmentation. The study was conducted on 5 surface mines. These were Mogalakwena Platinum Mine, Kolomela Iron Ore Mine, Sishen Iron Ore Mine, Isibonelo Colliery, and Navigation Colliery. The study involved collecting data on the existing fragmentation profile in the mine and the geological characteristics of the ore body. The data was then used to evaluate the performance of the BlastLogic software in predicting fragmentation distribution. The blasting parameters used to achieve this were blast hole diameter, burden and spacing, powder factor and geotechnical factors such as the geology of the rock to be blasted. By accurately predicting the fragmentation size, engineers and blasting experts can design the blast parameters, such as hole diameter, spacing, and powder factor, more precisely. This allows for better control over the size distribution of the blasted material. Also, knowing the expected fragmentation size allows for the selection of an appropriate amount of iii explosive energy. Using too much energy can lead to excessive fracturing and finer fragmentation, while too little energy can result in larger rock fragments. Proper energy management helps achieve the desired size distribution. The findings of this research demonstrated that the predicted fragmentation distribution created by using BlastLogic software is more effective and profitable than the conventional method. The predicted fragmentation size reduced the amount of oversized material generated during blasting, thereby improving the recovery rate of valuable minerals. The results showed that there were less than 15% of fines produced, with an insignificant amount of oversized material less than 5% for all surface mines under study. In conclusion, the study evaluated the use of BlastLogic software in predicting fragmentation distribution. The study further highlighted the results of vibration and overpressure results obtained from these improved designs from BlastLogic. It was evident that BlastLogic software is a valuable tool for improving the efficiency and profitability of mining operations. The software offered a more accurate and reliable method of predicting and improving blasting fragmentation distribution for surface mines.
Geostatistical Modelling of Floor and Roof Hazard Data in the Highveld Coalfield – A New Denmark Colliery Case Study
(University of the Witwatersrand, Johannesburg, 2024) Hall, Quintin
New Denmark Colliery (NDC) is an underground coal mine located between Standerton and Bethal in the Mpumalanga province of South Africa. Due to the nature of the coal seam and the mining method in the research study area, mining operations are in constant contact with floor and roof lithologies which introduce operational challenges. To mitigate these challenges floor and roof hazard plans are used for operational planning purposes. Existing floor and roof hazard plans are deficient of both sound theoretical and procedural formality in their construction. This lack of formality in the hazard modelling was most concerning. The research establishes a methodology for the generation of meaningful floor and roof hazard plans from empirical and theoretical applications to both interpreted and measured variables relevant to the floor and roof hazards encountered. This methodology; developed for easy operational implementation, is supported by a formal system of procedures that allow for continuous updating, validation and monitoring. The quantitative and qualitative hazard data available in the study area required bridging. For this, the author introduces the concept of applying scorecards to the hybrid data and develops the scoring logic to convert the hybrid hazard information to numeric values, usable in quantitative analyses. The estimation software in place at NDC is limited to inverse distance weighting (IDW). The research therefore sought to determine whether the application of this classical technique would suffice for the creation of hazard plans. IDW, ordinary kriging and conditional sequential Gaussian simulation were applied to measured structural variables. The estimation results were visually compared. This would then confirm the suitability of applying IDW to the research data. The research takes a turn when the hazard scorecard numbers become the focus of the research as opposed to the structural variables. Floor and Roof hazard scores are individually classified, respectively representing either iv “competent”, “moderately competent” or “incompetent” floor conditions and “normal”,” cautionary” or “high risk” roof conditions. An innovative method of defining hazard indicators sets is introduced. IDW estimation is applied to each hazard indicator set. Results are interpreted, and inflection points on the slopes of the cumulative distribution plots of the estimates are used to identify cut-off values to clearly distinguish the hazard conditions mentioned. Resulting in updated Floor Hazard and Roof Hazard Plans for NDC aligned to a formal analytical process and estimation methodology. With this in place, the research goals were accomplished through the construction and validation of reliable and easily implementable floor and roof hazard plans. Procedures for applying hazard scorecards to newly drilled boreholes and for updating the hazard models appear in the Appendices.
Quantification of the benefits of pumpable emulsion explosives in narrow reef gold mines
(University of the Witwatersrand, Johannesburg, 2024) Chosi, Ramphele Lordwick
Pumpable emulsion explosives usage is gaining ground in South African underground narrow reef mining following its wide application on the surface and underground massive mining. Following the advancement in the narrow reef, this research sought to quantify the benefits of pumpable emulsion explosives in narrow reef stopes of gold mines under non-trial conditions on three key performance areas (KPA) of cost of explosives, blasting efficiency and post-blast conditions. The study adopted both qualitative and quantitative methodological approaches where historical and primary data was collected at the identified underground shafts of Ya Rona and Hlanganani. Historical data included planned targets and achieved results before and after the introduction of pumpable emulsion explosives at the shafts. The primary data was gathered through a total of 33 underground observations at the two shafts. The analysis of three KPAs was done through corresponding KPIs of explosives cost, face advance, powder factor, fragmentation distribution, and hangingwall overbreak. The cost of explosives KPA analysis indicated that pumpable emulsion was cost-effective when compared to cartridge explosives and the planned target. The blasting efficiency KPA was analysed through three KPIs, namely, face advance, powder factor, and fragmentation. The primary data analysis showed that the pumpable emulsion explosives were capable of achieving the mine’s required face advance at both shafts, and the historical data analysis showed that pumpable emulsion explosives performed better at the Ya Rona shaft and poorly at the Hlanganani shaft. The pumpable emulsion explosives powder factor calculated iii from the underground measurements can be lower or higher than the corresponding planned powder factor due to in-situ site conditions. Blast fragmentation analysed images showed that pumpable emulsion explosives can achieve the mine expected range fragmentation size or be below as indicated by the two image analysis programmes used and the Kuz-Ram estimation. Post-blast conditions were analysed using the hangingwall overbreak which cautiously showed that emulsion explosives have the potential to negatively impact the panel's post-blast condition due to non-adherence to the blast design parameters and the influence of the geological conditions. The research KPAs of cost of explosives, blasting efficiency and post blast conditions through the respective KPIs have indicated that emulsion explosives could achieve blast outcomes that were within the mine target. The analysis of the cost of explosives, face advance and powder factor KPIs conclusively showed the positive outcome pumpable emulsion explosives could have in narrow reef mines; though the powder factor showed dependence on other factors. The analysis of hangingwall overbreak KPI revealed a possible negative impact, while the analysis of the fragmentation KPI yielded an inconclusive outcome. Based on the results, the study proved the effectiveness of pumpable emulsion in narrow reef stope mining under non-trial operational conditions. It also quantified the benefits of pumpable emulsion explosives in narrow reef gold mines. Notwithstanding, it is recommended that further research on fragmentation analysis using different analysis methods and more research on the extent of the hangingwall damage when pumpable emulsion explosives are used should be conducted.
Internal Cooling at the Trailing-Edge of a High- Pressure Gas Turbine Blade
(University of the Witwatersrand, Johannesburg, 2024) Schekman, Sjouke W.
The efficiency of a gas turbine engine tends to be increased when its turbine blades are operated at higher temperatures. In turn, this requires the adequate cooling of these turbine blades (for both rotors and stators, collectively termed “airfoils”). Of specific concern in this study is the cooling at the trailing- edge of the airfoils. However, there exists limited space for cooling due to a requirement for a thin trailing-edge. A combination of perforated blockage plates and a pin-fin array (a “blockage pin-fin” configuration) is particularly focused on here. Such a configuration has been previously discounted due to a presumed poor thermal performance ( hTP < 1.0). This thesis demonstrates that the thermal performance has been misrepresented in part due to a misunderstanding of flow behaviours present in the configuration. To this end, a series of experimental tests are undertaken using particle image velocimetry, oil-dye flow visualization, and thermochromic liquid crystal paints. The new results show that a thermal performance greater than one (i.e., hTP > 1.0) can be achieved for a blockage pin-fin configuration. Despite previous studies concluding otherwise there may be merit in the use of a blockage pin-fin configuration for internally cooling the trailing-edge of a turbine blade. Further, a unique flow topology, present in a blockage pin-fin configuration was revealed. Such a flow, termed as a “jet-pin” flow, and its interactions has been previously unidentified or misinterpreted.
Magnetically Enhanced Vacuum Arc Thruster for Nanosatellites
(University of the Witwatersrand, Johannesburg, 2024) Rencken, Tristan Mark
This dissertation describes the development and testing of a magnetically-enhance Vacuum Arc Thruster (VAT) with various cathode materials and magnetic field strengths. The thruster uses a Power Processing Unit (PPU) used to generate a high-voltage spike to initiate and maintain a high current arc discharge. A multi-layer solenoid coil is placed around the arc discharge to investigate the effects of pulsed magnetic fields on the ion density distribution. The VAT produces consistent arc discharges with a peak arc current of IApk ≈ 270 A with a pulse length of tp ≈ 3.5 ms for three cathode materials, Fe (iron), Al (aluminium), and Cu (copper). The magnetic field generator uses a separate capacitive discharge circuit which produces field strengths between⃗ B = 0 - 250 mT along the center line of the thruster. Research was conducted to determine the effects of applied magnetic fields to the ion density distribution of ions with the VAT plasma plume. Ion-to-arc current ratios were normalised to a baseline VAT to directly compare qualitative distributions for the various materials and magnetic field strengths. The application of a magnetic field results in the increase in peak ion-to-arc current ratios with a decrease in ion-to-arc ratios at higher angles from the center line. The increased peak and narrowing of the ion distribution suggests that the magnetic field causes ion collimation within the plasma plume. For 0 <⃗ B < 250mT, performance increase over the non-magnetic case is observed with the best percentage increase in thrust factor of 16.4% for Al, 10.8% for Cu, and 6.3% for Fe, obtained at⃗ B ≈ 150 mT. For⃗ B > 150 mT, the ion distribution is shown to result in higher ion-to-arc ratios at higher angles perpendicular to the center line resulting in greater momentum loss. The greatest thrust factor increase of Al was found to be as a result of the mass-to-charge ratio of the Al ion which is subjected to greater accelerations due to Lorentz forces. The application of an axial magnetic field was found to increase the thrust factor and result in improved VAT thrust performances.
Uncontrolled aerobatic tumble manoeuvre mechanics
(University of the Witwatersrand, Johannesburg, 2024) Piccolo, Stefano Fabrizio
Despite advancements in aerobatic aircraft, the issues concerning aerobatic flight safety remain largely unresolved with incidents occurring at airshows, during training and during private flights, even with stable, predictable and reliable aircraft. The likelihood of aerobatic incidents has increased as aircraft are now capable of being flown in even more dangerous, low energy scenarios. Spins or tumble manoeuvres are typically the origin of loss-of-control accidents. Such scenarios occur generally in manoeuvres that result in low energy states. This dissertation aims to understand the mechanics behind a low energy aerobatic manoeuvre. The positive 𝑔 tumble manoeuvre was selected as the manoeuvre to analyse, as it is one of the most difficult aerobatic manoeuvres to recover from. The Extra 330SC was selected as the model aircraft as it is one of the most popular aerobatic aircraft across all pilot skill levels. Additionally, the Extra Aircraft Corporation provided more information about the aircraft than any other aerobatic aircraft manufacturer. Methods to develop mass, inertial and aerodynamic data were explored. The aerodynamic data was extended to high angles of attack. Aerodynamic models for the wing, fuselage, horizontal stabiliser and propeller were considered. Generated mass and inertial data were compared to reference data and demonstrated good correlation. Static aerodynamic data was compared to published experimental data (where possible). Good agreement was shown between the generated data and test data. Considerations for surfaces exposed to propeller slipstream and rotational dynamics were considered. No literature was available for direct comparison of these considerations. A non-linear three degree of freedom model was developed to simulate the tumble manoeuvre. This was achieved by simplifying the equations of motion in the velocity axes. The velocity axes were appropriate in determining the flight path of the manoeuvre along with all affiliated parameters. The aircraft body axes were utilised in determining the rotational parameters during the tumble manoeuvre. Force components at high angles of attack were modelled in both the velocity and body axes. The current model does not include any lateral-directional forces or moments, assuming the manoeuvre is purely in the longitudinal plane. A tumble manoeuvre is possible for a very specific aircraft configuration. An upgraded engine and propeller slipstream effects are essential in performing the tumble manoeuvre. It was shown the entire manoeuvre could be completed in a horizontal distance of ≈ 50 m and a vertical distance of ≈ 15 m for manoeuvre entry velocities of 25 m/s, 30 m/s, 35 m/s and 40 m/s. Each of the minimum radius tumble manoeuvres occurred at the most rearward centre of mass location. An entry velocity of 30 m/s provided the smallest possible radius tumble. The entry to the manoeuvre requires large decelerations and normal forces that were beyond the lift limits of the wing. Both these requirements were met by orientating the aircraft at large pitch angles and subsequently large angles of attack. The large angles of attack resulted in large decelerating forces and orientated various aircraft force components, other than iii the wing, in the lift direction. Significant energy loses are seen through the manoeuvre resulting in large losses in airspeed and ultimately altitude. The risks associated with a tumble manoeuvre could be minimised by adjusting the normal forces and moments acting on the aircraft. By altering the propeller blade pitch angle, the normal forces and subsequently the moments from the propeller could be changed, altering the overall normal forces and moments acting on the aircraft. This resulted in a slightly larger overall manoeuvre but illustrated increased velocity values throughout the manoeuvre. A form of validation of the results was performed by comparing model results of tumble manoeuvres that were generated through a patchwork of images compiled from video footage of the manoeuvre. Good correlation was shown between the model data and video footage.
Constrained solutions to IFPPS by finite-dimensional approximation
(University of the Witwatersrand, Johannesburg, 2024) McDonald, Andr´e Martin; van Wyk, Anton
The inverse Frobenius-Perron problem (IFPP) refers to the probabilistic modelling problem that requires the design of a discrete-time, one-dimensional dynamical system (i) that is ergodic and (ii) generates a zero-input time response that possesses prescribed statistical metrics as specifications. Systems designed using solutions to the IFPP hold potential as highly efficient and versatile random signal generators as well as solutions to practical radar signal processing problems. Distinct formulations of the IFPP have appeared in the literature: IFPP-I: The system is designed such its zero-input response possesses a pre- scribed probability density function (PDF). IFPP-II: The system is designed such that its zero-input response simultaneously possesses a prescribed PDF and a prescribed power spectral density (PSD). IFPP-III: An unknown system is reconstructed from sequences of PDF estimates of its zero-input response, which are derived from measurements of the unknown system. The work presented in this thesis contributes towards IFPP-II and IFPP-III by developing novel methods that improve upon exiting solutions. These novel methods construct candidate systems that admit an exact finite-dimensional representation for the FPO, which governs the evolution of density functions of the system’s response. The finite dimensionality of the FPO yields practical analytical methods for designing dynamical systems with prescribed statistical metrics as specifications, and for the consistent reconstruction of unknown dynamical systems. However, the structure of these systems imposes restrictions on the statistical metrics that are realisable, and only permit the approximation of arbitrary metrics that may be prescribed. Examples are presented that demonstrate the realisation of power spectra with prescribable poles and multiple peaks that are adjustable, and the reconstruction of iii unknown systems with consistent branch monotonicity and power spectrum mode characteristics, using the novel methods. Although the application-specific design and performance evaluation of random signal generators constructed using the proposed methods are not considered in this work, it is anticipated that these methods will be of interest in applications such as low-complexity random signal generation for Digital Radio Frequency Memory (DRFM) systems.
A bottom-up smart city approach to solid waste management: the case of ICT-enabled waste reclaimers system in two South African cities
(University of the Witwatersrand, Johannesburg, 2023) Siwawa, Vincent
This study delves into the realm of waste management in the context of bottom-up smart cities, focusing on the implementation of an innovative ICT-enabled waste reclaimer system in Cape Town and Johannesburg, South Africa. The central inquiry pertains to the pivotal role played by the bottom-up smart city paradigm in addressing waste management challenges and fostering the inclusion of waste reclaimers within the framework of smart cities. The inadequacies inherent in prevailing top-down smart city approaches and techno-centric solutions extends to the lack of mechanisms within the conventional informal recycling system to furnish reliable, immutable, and transparent waste-related data, thereby compromising security. To address these challenges, a novel approach emerges, fusing the capabilities of the Internet of Things (IoT) and blockchain technology into the informal recycling sector. This ICT-enabled waste reclaimer system introduces a comprehensive framework encompassing training initiatives, the provisioning of protective equipment, smartphones to facilitate communication between households and waste reclaimers, measuring instruments, tricycles, and dedicated spaces for sorting and storing recyclable materials. Employing a qualitative research methodology, this study incorporates a blend of document analysis, integrative literature review, and semi-structured interviews with key stakeholders. The selection of case studies, namely BanQu, Kudoti, and Regenize, is underpinned by purposive sampling. An array of research instruments including webinars, photography, participant observations, and transect walks contribute to the rich data collection process. The study draws upon the socio-technical transition theory to sustainability and the Multi-Level Perspective (MLP) as conceptual frameworks to dissect the digital transformation of the informal waste sector through the lens of the ICT-enabled waste reclaimer system. Findings underscore the potential of this innovative system to foster symbiotic connections between waste reclaimers and stakeholders embedded within the recycling value chain. This, in turn, culminates in enhanced working conditions and augmented income for waste reclaimers. Crucially, the ICT-enabled waste reclaimer system offers mechanisms for waste monitoring and tracking, while concurrently introducing incentives and rewards. By generating precise, secure, and reliable data, this system engenders a paradigm shift from a conventional cash- based payment structure to a virtual and electronic payment mechanism. Preliminary evidence showcases a notable threefold increase in recyclable collection by waste reclaimers compared to municipal efforts. In culmination, this study delivers both theoretical and empirical contributions by shedding light on the integration of waste reclaimers and waste management within the context of a bottom-up smart city approach. The study posits a promising trajectory for future research and ushers in new avenues for the development of bottom-up smart cities within the ambit of developing nations.
Assessment of the Performance of Corn Cob Ash as a Partial Replacement for Portland Cement in Concrete
(University of the Witwatersrand, Johannesburg, 2023) Fadele, Oluwadamilola Adepeju; Otieno , Mike
The production of Portland cement is associated with the release of greenhouse gases especially carbon dioxide which is estimated to be about a ton per every ton of clinker produced contributing to climate change. Several mitigation strategies have been proposed but the most viable remains the use of supplementary cementitious materials as partial replacement for Portland cement. There have been considerable success with the use of some industrial by-products (fly ash and slag) and natural materials (calcined kaolin clay) as supplementary cementitious materials. However, the non-availability of these by-products in countries like Nigeria calls for the investigation of locally available substitutes. Supplementary cementitious materials are either pozzolanic or possess latent hydraulic properties making them choice materials as partial Portland cement replacement. The classification and choice of a material as supplementary cementitious material lies in the understanding of their characteristic properties (chemical composition and mineralogy) and subsequent performance in cementitious systems. The performance of corn cob ash calcined at 700°C and 800°C as partial replacement for Portland cement (PC) compared to Portland cement and fly ash (FA) was studied with the following objectives: to determine the influence of calcination temperature on the reactivity of corn cob ash; investigate the effects of corn cob ash content at varying w/b ratio on the i) hydration reaction of Portland cement; ii) the compressive strength of concrete iii) drying shrinkage strain of mortar iv) penetrability of concrete v) microstructure of concrete The laboratory investigation involves using corn cob ash to partially replace Portland cement at two levels of 15% and 30% by mass using two w/b ratios of 0.4 and 0.6 at a water content of 205 kg/m3. The corn cob ashes in binary combination with either Portland cement or fly ash were used to prepare concrete samples which were used for the determination of compressive strength, durability index tests (namely oxygen permeability, water sorptivity and chloride conductivity) to assess the durability of concrete, and microstructural development. The concrete was designed using the South African Cement and Concrete Institute method of mix design. Also, mortar samples made from one part of cement to three parts of sand were prepared for the investigation of drying shrinkage and estimation of strength activity index while paste samples were prepared for determining reactivity of the ashes and effect on Portland cement hydration. iv Reactivity of the ashes was measured using both strength activity index and R3 reactivity test. Strength activity index was estimated from the compressive strength of 50 mm cube mortars at the ages of 28, 56 and 90 days of curing in order to better understand the mechanism of reaction of the ash, while R3 test was performed on model paste using the bound water approach at the age of 7 days. The amorphous content of ash calcined at 700°C and 800°C is 1.9% and 2.4% respectively while the gain in strength of mortar cubes prepared with only Portland cement, Portland cement/fly ash, Portland cement/corn cob ash calcined at 700°C and 800°C between 28 and 90 days are 14%, 24%, 10% and 9% respectively. The surface area of the Portland cement, fly ash, corn cob ash calcined at 700°C and at 800°C is 2.38, 2.224, 3.122 and 2.751 m2/g respectively. The results indicate that the corn cob ashes (CCA) calcined at 700°C (C700) and 800°C (C800) are low reactive materials with limited pozzolanic reactivity while the mechanism of reaction is largely influenced by filler effect due to finer particle size than plain PC. The compressive strength of concrete containing 15% CCA calcined at 700°C and 85% Portland cement ranges between 40 to 58 MPa between 3 and 90 days of curing at w/b ratio of 0.4 compared to 56 to 83 MPa for Portland cement concrete and 48 to 82 MPa for fly ash/Portland cement concrete at the same replacement level. The porosity of concrete containing 15% C700 and C800 at w/b ratio of 0.4 is 9.66 and 6.9% respectively at 28 days of curing compared to 8.37% for PC and 6.52% for fly ash at the same age and replacement level. The presence of CCA affects the heat of hydration of plain PC by prolonging the induction phase by about 12 hours which delayed the evolution of main heat peak. The use of CCA lead to a reduction in strength compared to PC/FA system with compressive strength decreasing with increasing w/b ratio and increasing PC replacement level. CCA has a high potassium oxide content which is highly soluble with a high concentration in the pore solution of concrete. CCA influences volume change leading to a high drying shrinkage strain compared to plain PC and FA. CCA also affects the durability of concrete by increasing the penetrability of concrete which increases with increasing ash content. In terms of the studied properties of cementitious systems, there is no marked difference in the effect of C700 compared to C800 while the effects recorded becomes significant with increasing PC replacement level. In comparison to FA, the effect of CCA on the properties studied was inferior due to the largely crystalline nature resulting in limited pozzolanic activity

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