International Journal of Engineering Research in Africa Vol. 75

Abstract: The use of huge amounts of concrete has led to an increase in the focus on High Performance Concrete (HPC). This study examined how Waste Paper Pulp Ash (WPPA) pozzolanic qualities affected HPC. WPPA was used to replace PLC at levels of 5, 10, 15 and 20%, respectively. With a characteristic strength of 50N/mm², the COREN Mix Design Manual was followed in the adoption of the concrete mix design. A 150 by 150 by 150 mm concrete cube was cast, and it was cured in water for 7, 28, and 56 days. The X-ray fluorescence (XRF) method was used to ascertain the chemical composition of the WPPA. For fresh concrete, tests for compacting factor and slump were performed; for hardened concrete, tests for density and compressive strength were performed. The concrete gets less workable (stiff) as the proportion increases, according to the workability data. The compressive strength results at 56 days revealed that 5% of WPPA exceeded the 56.56N/mm² design target mean strength, 10% of WPPA met the 50N/mm² designed target mean strength, and 15% and 20% of WPPA fell short of both the designed target mean strength and characteristic strength. SEM analysis showed that up to 5% WPPA maintains a dense microstructure and high strength in concrete, while higher WPPA levels result in increased porosity and reduced mechanical performance. In comparison to traditional HPC, 5% WPPA replacement of PLC would result in concrete that is stronger after a longer curing period.

Abstract: Incorporating steel binding wire waste into concrete offers a sustainable solution that aligns with green construction practices. This study aims to explore the feasibility of using untreated steel binding wire (SBW) waste as a material in concrete production. This research examines the mechanical properties of concrete containing SBW as a partial replacement for sand to improve the concrete’s structural performance by addressing its inherent weakness in tension. Two different shapes of SBW (powder and fiber) and three ratios of replacement of sand by SBW (10%, 15%, and 20%) were considered. The obtained results demonstrate that incorporating SBW wastes enhances the fresh concrete workability. The increasement ranged from 15% to 35% for powder and fiber of SBW, respectively compared to the ordinary concrete (OC). When fiber SBW is added, the concrete density increases from 3.62% to 5.9% for 10% and 20% of SBW, respectively compared to OC. Whereas for powder SBW incorporation, it decreases from 1.7% to 0.37% for 10% and 20%, respectively. The addition of SBW fiber improves compressive strength (CS), which increases as the replacement ratio increases by 73% and 104%, for replacement ratios of 10% and 20%, respectively. However, a low ratio of SBW powder increases the compressive strength by 49%, while higher ratio results in a decrease in CS and the gain drops to 2%. Both SBW fiber and powder addition concrete demonstrate similar behavior in tensile strength (TS) as observed in compression. The study concludes that adding up to 20% SBW fiber and less than 10% SBW powder significantly enhances the mechanical properties of concrete, providing a practical method for waste utilization and material performance improvement.

Abstract: Expanded Polystyrene Aggregate Concrete (EPAC) offers reduced structural density and carbon footprint while maintaining acceptable mechanical performance, making it a promising material for sustainable, seismic-resistant construction. This study investigates the natural self-healing behavior of EPAC, a largely unexplored area, using the Taguchi method to analyze the effects of EPS percentage of total aggregate volume (60%, 70%, 80%), cement content (410, 515, 594 kg/m³), and W/C (0.45, 0.5, 0.55). A novel method developed in this study, quantified a maximum healing efficiency of 67.5%, with results indicating that higher EPS content enhances healing due to its elastic nature. Compressive strength, thermal conductivity, and density were also assessed to validate the method’s reliability. The findings demonstrate the utility of the Taguchi method in construction materials research by reducing experimental workload while maintaining analytical depth. The proposed healing assessment method opens new avenues for evaluating durability in EPS-based concretes, supporting future innovations in sustainable construction.

Abstract: This study presents a novel approach to optimizing concrete block production by utilizing coconut shells and coconut shell ash as sustainable alternatives to stone dust and cement. Using classical experimental-mathematical modeling and exponential regression analysis, the optimal material proportions and their influence on the mechanical strength of concrete blocks were determined. Chemical composition tests indicated that incinerating coconut shells enhanced key pozzolanic components—silicon oxide, iron oxide, sulfur oxide, and potassium oxide—significantly improving the ash's pozzolanic reactivity and the durability of the concrete mix. The results reveal a critical threshold for incorporating these materials: beyond certain proportions, compressive strength declines. Specifically, strength ranged from 16.14 to 26.77 N/mm² at 100% replacement and from 0.32 to 1.54 N/mm² at 75% replacement. A non-linear regression model based on 42 observation points was developed, with 39 used for model training. The model accurately predicts performance and indicates an ideal mix consisting of 82.58% stone dust, a water–cement ratio of 0.6039, 82.5% cement, 17.5% coconut shell ash, and 17.42% coconut shells. This mix achieved a compressive strength of 3.17 N/mm² after 14 days of curing, exceeding the required 2.9 N/mm². The practical implications of these findings suggest that this mixture is cost-effective, utilizing low-cost coconut shells instead of more expensive materials like cement and stone dust. This approach promotes the use of sustainable materials in concrete production, supports waste management and conservation efforts, and aligns with circular economy practices in construction. Furthermore, the developed non-linear regression model serves as a valuable tool for integrating agricultural byproducts into concrete block production, providing a reliable method for predicting concrete performance and enabling better material selection in future applications. Generally, this study offers recommendations for identifying the optimal concrete block mix, enhancing circular economy practices, and minimizing dependence on non-renewable resources

Abstract: The construction industry remains a major contributor to global CO₂ emissions, primarily due to its high consumption of non-renewable mineral resources and energy-intensive materials. In response to the growing need for sustainable alternatives, this study focuses on valorizing lignocellulosic biomass waste specifically Solid Olive Waste (SOW), a byproduct of olive oil production abundant in Mediterranean countries as a partial replacement for mineral aggregates in concrete. The main objective is to develop and evaluate an Innovative Solid Olive Waste Composite (ISOWC) as an eco-friendly material suitable for construction sector. The incorporation of SOW was optimized using the Talbot–Fuller–Thompson (T-F-T) semi-empirical method, which enabled the determination of ideal incorporation rates (10%, 20%, and 30% by aggregate volume) based on maximum packing density. Composite formulations were developed using the volumetric mix design method, incorporating both raw and water-saturated SOW. Comparative tests demonstrated that saturated SOW significantly improved the composite’s compressive strength and thermal conductivity, particularly as the SOW content increased. To further assess performance, a sensitivity analysis was conducted on ISOWC with 30% saturated SOW at varying cement dosages (200–350 kg/m³). The formulation with 200 kg/m³ cement achieved a compressive strength of approximately 6 MPa and thermal conductivity of 0.72 W/mK, meeting the criteria for insulating applications such as blocks and cladding panels. These results highlight the promising potential of ISOWC and support further investigation into the use of Solid Olive Waste as a full replacement for gravel in the development of eco-efficient, sand-based concretes.

Abstract: Improving the energy efficiency of thermal power plants through the thermodynamic analysis of their operational parameters in real time is a major issue in order to ensure rational and sustainable operation. An in-depth analysis has been conducted on the thermodynamic efficiency of three gas turbines in a gas/steam combined cycle power plant using real-time operational data. The presented work is part of the research that deals with operational parameters in order to maintain the performance of thermal power plants at the highest possible value. A combination of the first and second laws of thermodynamics has been developed to provide a model able of predicting the thermal efficiency of gas turbines in different operating modes in real-time. The results of our study indicate that each turbine demonstrated a thermal efficiency of around 33.5%. Additionally, the turbines produced an output power of 284 MW and had a specific fuel consumption rate of roughly 206 kg/MWh. The analysis not only verifies the durability of the turbines under various operating conditions, but also presents a verified method to monitor and improve energy efficiency in real time, which is crucial to optimize the power plant operations. Furthermore, this thermodynamic model can be used as a calculation program to be integrated into the display panel which will be used to provide operating indicators in real time. Keywords: Steam/Gas combined cycle, Gas turbine, Thermal performance, Energy conversion.

Abstract: This study presents a comprehensive energy audit and optimization strategy for six motor-driven pumps supplying hot water to essential production circuits in a food manufacturing facility. A Level II audit was conducted to diagnose network inefficiencies, including current and voltage harmonic distortions, power factor issues, and motor load conditions. A complementary demand-side analysis was also performed to align pump operations with actual process requirements and reduce energy losses. Adopting a systems approach, the study focuses on optimizing the overall motor system rather than analyzing components in isolation. Three energy-saving measures were proposed: (i) avoiding idle operations through solenoid valves, (ii) reducing motor power consumption with variable speed drives (VSDs) to match the process-required flow rates, and (iii) optimizing heating to prevent excess water temperature and unnecessary energy consumption. These measures led to substantial energy and cost savings—specifically, annual reductions of 44,079.25 kWh of electricity and 2,921 GJ of thermal energy, equivalent to $67,187 in financial savings and a 214.38-tonne reduction in CO₂ emissions. With payback periods as short as 0.7 years, the proposed actions are economically viable and practically implementable. This research contributes to filling the gap in real-world case studies on industrial energy optimization, particularly in developing countries, by demonstrating that significant savings can be achieved through simple, low-cost interventions. It thereby helps break down the barriers that prevent industries from adopting energy efficiency measures. Despite the specific industrial context, the findings are broadly applicable across sectors due to the widespread use of motor systems. Moreover, the study supports both the African Union’s Agenda 2063 and the United Nations Sustainable Development Goals (SDGs) by offering actionable insights for enhancing energy efficiency and sustainability in the industrial sector.

Abstract: Pipelines are critical assets for transporting liquid and gaseous products in the oil and gas industry, and they are typically situated in challenging operational environments. Over time, adverse operational and environmental conditions lead to wear and tear of their structural components, resulting in structural anomalies that manifest as leak points. An effective pipeline anomaly and leakage detection mechanism is therefore crucial to maintaining the integrity of the product transportation system. This study develops a Long Short-Term Memory-AutoEncoder (LSTM-AE) model for real-time anomaly and leak detection in oil-and-gas production pipelines. The developed model uses an ensemble approach to adapt a multi-layer Long Short-Term Memory (LSTM) to improve the performance of an AutoEncoder (AE). The resulting hybrid LSTM-AE model composes an encoder, a repeat vector, and a decoder with a data-driven capability. The performance of the developed model is evaluated using publicly available oil-and-gas production data. Results indicate that the base AE model achieves accuracy, recall, and precision rates of 72%, 72%, and 100%, respectively, whilst the LSTM-AE model achieves improved rates of 88%, 100%, and 100% for the same respective metrics. The realized performance enhancement gives credence to the utility of the LSTM-AE model for effective intelligent anomaly detection in pipeline systems.

Abstract: Under both typical and partial shading conditions, this research seeks to assess how two maximum power point tracking (MPPT) solutions, Perturb and Observe (P&O) and fuzzy logic control (FLC), help maximize power extraction from a photovoltaic (PV) system. Applying MATLAB SIMULINK, a DC-DC converter and a PV generator were simulated to run these MPPT systems. The comparison focuses on the extracted power, the performance of each technique, and their ability to follow the global maximum power point (MPP). The simulation findings show that in standard and partial shading conditions, both P&O and fuzzy logic algorithms can effectively track the MPP. The fuzzy logic controller, however, turned out to be more accurate and efficient (≥98% efficiency vs. P&O's 97%) with minimal power oscillation, while the P&O algorithm had a faster response time.