DEPARTMENT OF STRUCTURAL ENGINEERING

This research addressed the critical need for effective culvert design and associated energy dissipators in Nigeria, aiming to enhance flood resilience in the face of increasing urbanization and climate change. The study developed design methodologies tailored to Nigeria's unique hydrological conditions, focusing on sustainability and optimizing culvert performance. The research acknowledged that culverts are essential structures for ensuring drainage, managing storm-water runoff, and protecting road infrastructure. The methodology involved a comprehensive hydrologic analysis based on rainfall data using rational method to estimate peak flow rates for various storm events. Field data was collected in Kajola, Ibeju-Lekki, Lagos State. Hydraulic design principles were then applied to determine appropriate culvert sizes, shapes, and materials, considering both inlet and outlet control conditions. Energy dissipation techniques, such as stilling basins, were evaluated to manage water energy at culvert outlets and minimize erosion, all through manual calculations and established formulas. The hydrological analysis, revealed a peak flow rate of 3 m³/s. Based on these results, a culvert with a diameter of 1.4 meters and a headwall height of 1.43 m was designed, optimized to handle an outlet velocity of 10.6 m/s on a slope of 0.077, with inlet control. Values for the Froude number at its supercritical depth and mean velocity fell within ranges suitable for a USBR Type III stilling basin geometry. The study recommended implementing a USBR Type III stilling basin to mitigate downstream erosion. It was concluded that these optimized design approaches improve culvert functionality, reduce maintenance costs, enhance environmental protection, and contribute to the development of improved design guidelines for engineers and planners in flood-prone areas.

The significance of housing in mankind history cannot be overstressed. However, many Nigerians cannot afford to own a building due to high cost of building materials. Recognizing the prevailing challenges, crises arising from shortage of low-cost housing necessitate a sustainable solution using new innovation and technology that is capable of fostering housing delivery. Nigeria's construction industry has been under pressure to adopt a modern, timely, and premium construction strategy to solve that problem by developing a cost-effective system of producing low-cost houses. This research aims to assess the role dry construction technique in ensuring affordable housing in Nigeria. The study employed both qualitative and quantitative research approach. A survey design was employed, and copies of the questionnaire were administered to stakeholders in the housing sector including construction companies, architects, engineers, real estate developers, and residents of Benin metropolis. Seventy (70) participants were purposefully selected. In addition, in-depth interviews with key stakeholders, such as real estate developers and architects, were conducted to provide deeper insights into the challenges and opportunities of implementing dry construction techniques. Data gathered were analysed using both descriptive and inferential statistics. The inferential analysis was conducted to assess the relationship between the use of dry construction techniques and the affordability of housing in Nigeria. A chi-square test was performed to determine whether a statistically significant association exists between these variables. The results of the chi-square test support the study’s primary objective, confirming that dry construction techniques play a significant role in improving housing affordability in Nigeria. This finding underscores the importance of promoting the adoption of innovative construction methods to address the country’s housing deficit and provide cost effective, high-quality housing solutions.

The intelligent partial replacement of fine aggregate with periwinkle shell in sandcrete blocks have emerged as a sustainable approach to address the environmental and economic challenges associated with conventional sanderete block production. Periwinkle shells, a marine waste abundant in coastal regions like Nigeria, are primarily composed of calcium carbonate (-95%) and have a low specific gravity (1.3-1.4 g/em'), making them a viable lightweight substitute for river sand. Studies, such as those by Ichetaonge et al.(2023) and Osarenmwinda and Aigbogun (2017), demonstrate that replacing fine aggregate with crushed periwinkle shell (CPWS) at levels up to 15% achieves compressive strengths of 2.0-3.0 MPa, meeting the Nigeria Industrial Standard (NIS 87:2000) for non-load bearing walls. The well-graded particle size distribution of CPWS (coefficient of uniformity = 6.58) enhances its suitability, but its high water absorption (10-20%) and reduced workability necessitate optimized mix designs, often incorporating admixtures like superplasticizers or pozzolanie materials such as fly ash to improve performance. The mechanical and durability properties of CPWS-based sandcrete blocks are influenced by replacement levels, mix proportions, and curing methods, Research indicates that compressive strength decreases with higher CPWS content, with significant reductions beyond 20% replacement (c.g., 18.00 N/mm? at 50% replacement, Osarenmwinda and Aigbogun, 2017). The use of CPWS promotes environmental sustainability by reducing reliance on river sand. mitigating the ecological damage caused by dredging, and repurposing marine waste, thus supporting circular economy principles (Ede et al., 2016). Also CPWS-based blocks reduce
construction costs by 15 -20% and create local jobs through shell processing.

Fire exposure destroys concrete structures, and the cooling methods significantly impacts residual strength Rapid cooling, especially with water, may cause additional damage due to thermal shock, yet limited studies compare air- and water- cooling effects. In order to determine which cooling technique best maintains structural integrity, this study will examine how various techniques affect the breaking strength of Grade 30 concrete exposed to temperatures of 200°C, 400°C, and 600°C. This study involves the preparation of Grade 10 concrete specimens, which were cured for 28 days before being subjected to elevated temperatures of 2000C 400C and 600°C in a controlled furnace. After exposure, the specimens were cooled using air and water to compare the effects of each method on compressive strength. The compressive strength of all samples was tested using a compression testing machine, and the results were analyzed through tabular and graphical comparisons to evaluate strength reduction trends. The study revealed that compressive strength decreased with increasing temperature, with watercooled samples experiencing greater strength loss than air-cooled due to rapid thermal shock. At 600°C, Average water-cooled samples record 26.561 N/mm², while air-cooled samples record 28.014 N/mm², confirming that gradual cooling helps to retain more structural integrity. Based on these findings, air cooling is recommended as a safer and more effective method for post- fire concrete recovery. Further research should explore advanced cooling techniques to enhance fire resistance and durability.

This project aimed to conduct a comprehensive geotechnical analysis of laterite soil from the Obviogie Borrow Pit, with the goal of assessing its suitability for use in road construction and developing a data bank for future reference. Laterite soils were commonly used in road construction, particularly as sub-base and sub-grade materials, due to their availability and cost-effectiveness. However, it was crucial to evaluate the physical properties of the soil to ensure it met the engineering requirements for long-lasting and stable roads. For this study, a soil sample was collected from the borrow pit and subjected to various laboratory tests to determine its key physical characteristics.
The analysis focused on fundamental properties such as moisture content, specific gravity, and particle size distribution. These factors played a significant role in understanding the behavior of the soil under load and during compaction. These parameters were essential for establishing the soil’s ability to support heavy loads when used as a sub-base or sub-grade material in road construction. The data gathered from the physical and compaction tests were compiled into a detailed data bank. This data bank served as a valuable resource for engineers and road construction professionals, providing them with critical information to guide the selection, preparation, and compaction of the soil for use in road building projects. By offering a clear understanding of the soil's load-bearing capacity and compaction behavior, this project helped ensure that roads constructed in the Obviogie region were built on a solid foundation, enhancing their durability and reducing the need for costly repairs in the future.
The overall goal of this project was to support the use of local materials in road construction while ensuring that they met the necessary engineering standards. This study contributed to the efficient use of laterite soils, which were widely available in the Obviogie area, and helped reduce construction costs by minimizing the need for imported materials. In doing so, the project provided valuable insights that promoted more sustainable and cost-effective infrastructure development in the region.

This project work was created in order to highlight and present the findings froma studyon the "EFFECT OF IMPROPER CURING ON THE STRENGTH ANDTRANSPORTPROPERTIES OF LOW GRADE RICE HUSK ASH (RHA) CONCRETE" withthegoal of understanding how various curing techniques for 3, 7, 14 and 28 days affect theachievable compressive strength and other structural properties of a lowgrade concretesuch as 20MPA having Ordinary Portland Cement (OPC) (an agriculturally basedpozzolanic material, lying in abundance around the globe most times as waste, foundsuitable by researchers to partially replace OPC in the production of concrete). After designing a low grade concrete mix with a goal mean strength of 20N/mm2, anumber of concrete mixtures cast into 100mm metallic cubes were made in the labusingOPC as the binder (partially substituted with RHA at various percentages). Inafog/curing room with ambient temperatures between 30 and 20 °C and lowrelativehumidity (RH), three different types of "curing methods" (a moisture management balancing act) were used for these samples. The first series of cubes cast after demoulding were fully submerged in water and cured at 100% RH for the durationof itscuring period (signifying wet curing). The final set of cubes cast were completelycuredout in open air without any water submerging after demoulding (signifying dry/air curing), while the other set of cubes stayed in water for 3 days after demouldingas well and then continued to cure for the remaining curing period at a relatively lowhumidity. Therefore, performance was assessed in terms of compressive strength, transport properties, and other tests conducted. It was found that while the strength of RHAconcrete continued to decline after the addition of 15% RHA, the replacement level of 5% RHA gave the strongest results overall and demonstrated the greatest potential tobeused as a useful material for various building materials. The partial replacement of RHAwith OPC can be seen to have a positive impact on the environment by reducingtheamount of agricultural waste produced, which results in more cost-effective andenvironmentally friendly concretes than those currently used in the industry.

This work investigated the possibility of using waste concrete materials as partial replacement for coarse aggregates in concrete work and some of the properties of Recycled concrete aggregates. The Recycled concrete aggregate used was gotten from waste samples in the laboratory of the Department of Civil/Structural Engineering of the University of Benin. These samples were dried and crushed, they were used to replace Natural Coarse Aggregate under different percentage of 0%, 20%, 40%, 60%. The test done was Aggregate Impact Value (AIV), Sieve Analysis, Slump Test, Compressive Strength and Split Tensile Strength Test. With a total of 36 cubes and 36 cylinder made, curing age of 7, 14 and 28 days were used to investigate the strength of the concrete made. The results obtained show that the aggregate impact value of Natural coarse Aggregate was 27.43% and that of Recycled concrete Aggregate 35%. Slump value for 0%, 20%, 40%,60% are 40.50, 30.50, 30.30, 30.70mm. The compressive strength test of 0% is 23.30N/mm2 at 28 days, 20% is 28.11 N/mm 2 at 28 days, 40% is 20.10N/mm2 at 28 days, 60% is 26.96 N/mm2 at 28 days, and the split tensile strength of 0% is 2.69 N/mm2 at 28 days, 20% is 2.75 N/mm2 at 28 days, 40% is 1.78 N/mm2 at 28 days, 60% is 2.18 N/mm2 at 28 days. It was seen that Recycled concrete aggregate (RCA) decreases with increase in percentage of replacement and the maximum or optimum strength was obtained at 20% replacement.

A water supply system's pump design and selection are essential to guaranteeing a dependable and effective water distribution to satisfy the needs of different users, such as commercial, industrial, and residential customers. Pumps are essential components of water supply systems because they supply the energy needed to lift water to higher storage tanks or reservoirs, overcome pipe flow resistance, and maintain the necessary pressure across the distribution network. Choosing and designing a pump system for a water supply system that satisfies the necessary flow rate and pressure head while guaranteeing dependable and effective operation is the aim of this project. A detailed understanding of the hydraulic needs of the system, such as the flow rate, pressure head, and friction losses, is necessary for designing a pump system for a water supply system. The kind of pump, pump size, impeller design, and motor selection are just a few of the variables that must be carefully taken into account throughout the pump selection process. Among the many advantages of a well-designed pump system are greater system reliability, lower maintenance costs, and energy economy. It might be difficult to choose a pump that satisfies the needs of the system while reducing energy consumption and expenses since pumps in water supply systems frequently have to function throughout a broad range of flow rates and pressures. The pump system must also be built to handle seasonal variances, demand variations, and possible future system additions or improvements. Choosing and designing a pump system for a water supply system that satisfies the necessary flow rate and pressure head while guaranteeing dependable and effective operation is the aim of this project. It is possible to build and choose an appropriate pump system to satisfy the demands of the water supply system by thoroughly examining the hydraulic requirements of the system and the pump performance characteristics.

This study presents a comparative evaluation of the strength characteristics of concrete using both non-destructive (rebound hammer) and destructive (compressive strength) testing methods. The primary aim of the research was to determine the correlation between rebound hammer readings and actual compressive strength values of concrete produced from different mix ratios; 1:2:4 (C20), 1:1.5:3 (C25), and 1:1:2 (C30) under proper compaction and curing conditions. The investigation was motivated by the need to establish a reliable, quick, and non-invasive method for assessing the in-situ strength of concrete structures while maintaining compliance with international testing standards. The experimental program involved casting 100 mm × 100 mm × 100 mm concrete cubes for each mix ratio. The cubes were cured for 7, 14, and 28 days, after which they were tested using a Schmidt rebound hammer in accordance with BS EN 12504-2:2012 and ASTM C805, and a compressive testing machine following BS EN 12390-3:2019. In addition, a sieve analysis was performed on both fine and coarse aggregates to determine their particle size distribution and compliance with BS 812 (Part 103.1:1985) standards. Statistical regression analysis was also conducted to develop mathematical relationships between rebound number and compressive strength, and to determine the coefficient of determination (R²) for each mix ratio. The results indicated that concrete strength increased consistently with both higher cement content and longer curing periods. At 28 days, average compressive strengths of 17.89 N/mm², 25.92 N/mm², and 31.52 N/mm² were recorded for C20, C25, and C30 grades respectively. The rebound hammer results were found to underestimate compressive strength by about 5–10%, but showed a strong correlation, with R² values of 0.85 (C20), 0.96 (C25), and 0.98 (C30). The findings confirm that while the rebound hammer test cannot replace compressive testing for structural verification, it is a valuable non-destructive tool for rapid field assessment and comparative strength evaluation. Proper calibration using laboratory data is essential to ensure reliable application in insitu concrete quality control

This study investigates the properties of limestone calcined clay cement (LC3) with a water/cement ratio of 0.5 and cement/sand ratio of 1:2.75 produced using clay sourced from Uzebba, Nigeria. The kaolinitic Uzebba clay was calcined at 600°C, 700°C and 800°C to activate it's pozzolanic properties. Mortar cubes were cast and cured in lime water and by air. A total of 120 mortar cubes were prepared for compressive strength testing and water absorption test. For compressive test, 9 cubes were mixed and cured in lime water and air serving as the control, 27 cubes were mixed for LC 3 calcined at 600°C, 700°C and 800°C for 30% and 40% replacement and cured in lime water and by air. Additionally, this study utilized other tests like sieve analysis of fine aggregate, standard consistency test, setting time of cement and bleeding tests. The average compressive strength for 30% and 40% mortar cubes cured in lime water ranged from 9.44N/mm2 - 17.12N/mm2 and 7.47N/mm2 - 12.16N/mm2 respectively, while for 30% cured in air ranged from 5.70N/mm2 - 15.91N/mm2 For water absorption test, 12 cubes were mixed and cured in lime water to determine the amount of water absorbed by the cubes for the control and replacement.