DEPARRTMENT OF STRUCTURAL ENGINEERING

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.

Ugbowo Road in Benin City faces persistent flooding and drainage failure driven by rapid urbanization, poor maintenance, and structural decay. This study assessed the structural integrity and hydraulic efficiency of drainage sections at four key locations: UBTH, Adolor Junction, Uselu Shell, and Ekehuan Link Road. Through visual inspections, non-destructive rebound hammer testing, and hydraulic analysis using Manning’s and Rational Methods, the research aimed to identify specific causes of failure and propose viable technical solutions. The investigation revealed significant structural defects, including cracks, erosion, and honeycombing, with concrete compressive strengths (12.7–19.8 MPa) falling below the required 20–25 MPa standard. While hydraulic analysis confirmed that the original designs possessed sufficient capacity to handle peak discharges, their performance is currently crippled by heavy siltation, waste dumping, and poor slope alignment. Consequently, the study identified functional inefficiency and maintenance neglect, particularly at the critical Adolor Junction rather than design inadequacy as the primary drivers of drainage failure. To restore optimal functionality and mitigate urban flooding, the study recommends the
reconstruction of failing sections using 25 MPa concrete and the implementation of a rigorous maintenance regime involving routine desilting. Technical enhancements, such as the installation of trash screens and inspection chambers, should be paired with the enforcement of environmental sanitation policies. Finally, the establishment of a drainage asset management plan by the Edo State Ministry of Works and Environment is essential for the long-term monitoring and sustainability of the corridor's infrastructure.

This study focuses on evaluating the relationship between destructive and nondestructive testing methods for predicting the in-situ compressive strength of concrete. The main aim is to develop a reliable regression-based model capable of estimating concrete strength using non-destructive approaches. The study specifically examined Grade 20 (C20) and Grade 25 (C25) concrete to determine the correlation between rebound hammer results, and conventional compressive strength tests. The experimental procedure involved casting and curing concrete cubes and beams in the laboratory under controlled conditions. Both destructive tests (compressive and flexural strength) and non-destructive tests (rebound hammer) were carried out at curing ages of 7, 14, and 28 days, following BS EN 12390-3:2019, ASTM C39, and BS EN 12504- 2:2012 standards. Rebound hammer readings were taken before compression tests on each specimen to establish a correlation between rebound number and actual strength. The data obtained were analyzed statistically using regression techniques to develop predictive models capable of estimating compressive strength from non-destructive test results. The findings revealed that compressive and flexural strengths increased consistently with curing age for both concrete grades. At 28 days, C20 achieved an average compressive strength of 20.16 N/mm², while C25 reached 25.15 N/mm², aligning with their design targets. Rebound hammer values showed a strong positive correlation with destructive test results, with a prediction accuracy of about ±5%. The study concludes that properly calibrated non-destructive methods, particularly the rebound hammer tests, can effectively predict the in-situ compressive strength of concrete. This approach provides a cost-effective, rapid, and non-invasive means for quality control and structural assessment in modern construction practice.

This project aims to evaluate the strength of concrete by partially replacing the coarse aggregate by Blast Furnace Slag (BFS). The primary objective is to determine the effect of replacing natural granite with BFS in varying percentages (2.5%, 5%, 7.5%, and 10%) on the strength and durability of concrete. The research is motivated by the need to find sustainable alternatives to natural aggregates, reduce construction costs, and promote the reuse of industrial by-products in the construction industry. The methodology involved preparing concrete mixes with BFS replacing granite at 0%, 2.5%, 5%, 7.5%, and 10% by weight. The materials to be used include Ordinary Portland Cement, fine aggregates (sharp sand), coarse aggregates (granite and BFS), and potable water. Standard laboratory tests were conducted, including sieve analysis for particle size distribution, slump test for workability, compressive strength and flexural strength tests at curing ages of 7, 14, and 28 days, and Aggregate Impact Value (AIV) and Aggregate Crushing Value (ACV) tests to assess aggregate quality. A constant mix proportion was maintained for all specimens, with curing performed under controlled conditions to ensure comparability of results.The results revealed that the control mix (0% BFS) achieved the highest compressive strength of 21.08 N/mm² and flexural strength of 9.60 N/mm² at 28 days, while 2.5% BFS replacement yielded comparable strengths of 19.29 N/mm² and 8.56 N/mm², respectively. Workability decreased with increasing BFS content, with slump values reducing from 30 mm (control) to 16 mm (10% BFS). The AIV and ACV values confirmed that both aggregates were mechanically durable, though granite performed slightly better. It was concluded that BFS can be used as a partial replacement for granite up to 2.5% in structural concrete without significant loss of performance, while higher percentages are more suitable for non-structural applications.

The aim of this project is to determine the effects metakaolin powder has on the mechanical properties of concrete when partially replaced at various percentages (15%, 20% and 25%). The idea behind this study is to assess if metakaolin powder can serve as a suitable substitute for sand as a fine aggregate in terms of responses to various tests. This study seeks to serve as a guide for future research in this field. It also serves to answer the question of why seek substitutes for fine aggregate at all.The tests required for accomplishing this experiment’s objectives are the compressive, flexural, slump and density tests, to determine the compressive strengths, flexural strengths, workability and density, respectively, of various samples been tested. Conventional concrete samples are cast and compared to partially replaced concrete to analyze the effects on concrete. The results for various tests differ showing rises and falls in strengths, slumps and densities. These results are then compared using tables and charts, from which a conclusion is drawn. The conclusion drawn for workability is that it has a low workability due to the pozzolanic nature of metakaolin powder and its reaction to cement and for the strengths, it is ascertained that concrete samples experience an increase in strength at 15% of partial replacement followed by a decrease at 20% and an increase at 25% indicating a possibility of later strengths at higher percentages but more so at longer periods of curing.

This research project investigated sustainable resource recovery and characterization strategies for sludge waste generated by Seven-Up Bottling Company's manufacturing operations in Oluku, Benin City, Edo State, Nigeria. The study comprehensively characterized sludge waste streams from three primary sources within the facility: water treatment plant sludge from clarification processes, cleaning sludge from equipment washing operations, and storage tank sludge from ingredient preparation areas. The research employed systematic sampling and analysis approaches following standard laboratory procedures, with comprehensive physicochemical analysis conducted at the Civil and Structural Engineering Laboratory of the University of Benin. Physical properties including total solids, volatile solids, and moisture content were examined through oven-drying at 105°C and loss on ignition at 550°C.
The results revealed highly favorable characteristics for beneficial reuse applications. The cleaning sludge exhibited a near-neutral pH of 6.9, falling within the optimal range (6.0-7.0) for agricultural crop production, and moderate electrical conductivity of 506 μS/cm, indicating appropriate salt content without salinity risks. The sludge contained valuable plant nutrients including elevated levels of calcium (6.41 mg/L), magnesium (4.71 mg/L), phosphorus (0.241 mg/L), and various nitrogen forms (ammonia nitrogen: 0.330 mg/L, nitrate: 0.283 mg/L), making it suitable as a soil amendment or fertilizer component
The study concludes that Seven-Up Bottling Company's sludge waste possesses excellent characteristics for resource recovery and beneficial reuse, particularly for agricultural applications. The combination of favorable nutrient content, near-neutral pH, low heavy metal concentrations, absence of petroleum contamination, and minimal pathogenic microorganisms demonstrates the sludge's suitability for transformation from an environmental liability into a valuable resource. This research provides the technical foundation for implementing sustainable waste management practices that align with circular economy principles while generating environmental and economic benefits for the company and surrounding agricultural communities.