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- ItemGeotechnical Properties of Surfactant Modified Lateritic Soils(Springer Nature, 2025-11-25) Olubunmi Oluwadare Owoyemi; Lekan Olatayo Afolagboye; Godwin Babatunde EgbeyaleSurfactants may exist in soils as contaminants or as additives for soil remediation and stabilization. The effect of different types of surfactants containing soaps on important geotechnical properties of lateritic soil samples from Oro and Ajase Southwestern Nigeria was investigated here. The soils in their natural state were characterized using specified standard geotechnical methods, X-ray Diffractometry (XRD) and X-ray fluorescence respectively (XRF). The soil samples were modified with liquid soap, bar soap and detergent and the effect of this contamination on important geotechnical properties such as Atterberg limits, bulk density, specific gravity, compaction, permeability, California bearing ratio (CBR), matric suction and shear strength parameters of the soils were investigated. Soils from both locations contain kaolinite, quartz and goethite in varying percentages, while silica, aluminium and iron oxide are the dominant oxides. The addition of surfactants in the three soap types resulted in an increased plasticity index of up to 93%, cohesion and optimum moisture content in soils from the locations. Bulk density, maximum dry density, angle of internal friction and permeability are reduced in them. Matric suction increased in all the soils with the greater increase recorded in the ones modified with liquid soap. These changes are attributable to the dispersion of clay minerals in the soils. Oro soil with a higher percentage of kaolinite is more sensitive to surfactants. The effect of surfactant-containing soaps on the geotechnical properties of lateritic soils vary based on mineralogy and surfactants type.
- ItemGEOCHEMISTRY, MICROSCRUCTURE AND PHYSICAL PROPERTIES OF THERMALLY STRESSED METAMORPHIC ROCKS(Malaysian Journal of Geosciences, 2027-04-07) Olubunmi Oluwadare Owoyemi; Lekan Olatayo AfolagboyeMetamorphic rocks are useful in many heat-based geotechnical facilities since they are believed to be strong and durable due to their crystalline nature. However, rocks get degraded under repeated thermal stress. This work evaluates the effect of repeated heating and cooling on the geochemistry, mineralogy, microstructure and physical properties of some metamorphic rocks from the Nigerian Basement Complex. Effect of cooling condition was also investigated. Marble, granite gneiss and banded gneiss were subjected to fifty cycles of heating and cooling in air and water using heating temperature between 100 oC and 700 oC. Marble samples used in the study completely disintegrates at the 35th cycle of heating and air-cooling at 500 oC. They could not withstand more than 26 cycles of heating and air-cooling at higher temperature of 700 oC. The porosity, water absorption and degradation degree are highest in marble and least in granite gneiss. The crushing strength of both samples of granite gneiss is higher than that of banded gneiss and marble. Similar trend was observed in the residual values of these physical properties after fifty thermal cycles. Microstructural imagesshowed micro-cracks in the thermally stressed rocks. However, no changes in mineralogy and geochemistry were recorded in the rocks. The water - cooled samples exhibited greater degradation than the air-cooled ones. Granite gneiss is more resilient than banded gneiss while both gneisses are more durable than marble. Metamorphic grade appears to play a major role in the resilience of the rocks to degradation.
- ItemImpact of Crude Oil Contamination and LowTemperature Thermal Desorption on Soil Properties and Remediation Efficacy(Taylor and Francis, 2025-10-03) Olubunmi Oluwadare Owoyemi; Lekan Olatayo Afolagboye; Megan WelmanPurchase; Damilola Tope OgundeleCrude oil contamination significantly alters soil properties, posing environmental risks and challenges for sustainable development. This study investigates the potential of low-temperature thermal desorption (LTTD) at 110°C as an environmentally friendly remediation technique for crude oil-contaminated soils. Soil samples contaminated with crude oil from Nigeria’s Niger Delta were analyzed for changes in Atterberg limits, specific gravity, linear shrinkage, sodium percentage (PS), and total dissolved solids (TDS). After LTTD treatment at 110°C for 30 minutes, the soils were assessed using gas chromatography, Fourier transform infrared spectrometry, X-ray diffraction, and scanning electron microscopy to evaluate microstructural and mineralogical changes. Contamination increased plasticity, shrinkage, and dispersivity, while reducing specific gravity. LTTD successfully removed up to 96% of hydrocarbons, but also caused a 15% weight change and minor alterations in hydrocarbon functional groups. Scanning electron microscopy revealed particle agglomeration after remediation, which may help counter the increased dispersivity caused by contamination. X-ray diffraction showed no significant mineralogical changes in the remediated soils. LTTD at 110°C proves effective in reducing hydrocarbons and mitigating crude oil-induced soil degradation, contributing to sustainable environmental management.
- ItemVariation in bulk density of granitic rock samples at mild temperature range(Published by University of Tehran., 2025-12-23) Lekan Olatayo Afolagboye; Adenike Helen Adedeji; Olubunmi Oluwadare Owoyemi; Yusuf Ademola Abdu-RaheemNumerous laboratory investigations have explored the properties of various rocks subjected to high temperatures rarely encountered in rock engineering applications. This study investigates investigate the variation in bulk density of fine-grained granite (FGG) under mild temperatures (20°C–200°C), relevant to rock engineering applications such as geothermal systems and radioactive waste storage. The objectives are to quantify changes in mass, volume, and bulk density of FGG samples and identify underlying mechanisms through microscopic analysis. Cylindrical core samples (50 mm diameter × 100 mm height) were extracted from a granite outcrop in Ado-Ekiti, southwestern Nigeria, with a core drilling machine, following ISRM standards. Mass and volume were measured before, during, and after heating at 20°C intervals up to 200°C in an electric oven. Bulk density was calculated using ISRM standards based on the measured mass and volume at selected mild temperature intervals. Results show a decrease in mass and an increase in volume with rising temperature, leading to a reduction in bulk density. The average percentage of mass loss,volume increase, and bulk density decrease was higher during heating than after cooling. In addition, microscopic analysis indicated a progressive increase in microcrack density, with distinct trans-granular cracks forming across feldspar grains at 200 °C. The findings reveal the potential impact of mild thermal exposure on granite’s structural integrity, which is relevant for rock engineering applications in environments subject to moderate thermal fluctuations.
- ItemImpact of moderate and high-temperature cyclic heating on lateritic soil properties(Springer international Publishing, 2026-11-26) Olubunmi Oluwadare Owoyemi; Lekan Olatayo Afolagboye; Megan Welman-Purchase; Charles Adebayo OyelamiThis study examines the effects of cyclic moderate and high-temperature heating on the mineralogical, microstructural, and geotechnical properties of lateritic soils. Residual soils from Akerebiata (AK) and Ipetu (IP), southwestern Nigeria, were subjected to five heating–cooling cycles at 300 °C and 500 °C, using a heating rate of 5 °C/min. Mineralogical and microstructural changes were evaluated using X-ray diffraction (XRD) and scanning electron microscopy (SEM), while geotechnical properties were assessed using standard laboratory tests and supported by one-way and two-way ANOVA with Tukey’s HSD post-hoc analysis. Cyclic heating caused significant mineralogical alteration in the feldspar-rich AK soil, marked by a reduction in plagioclase and an increase in quartz content. In contrast, the kaolinite quartz-dominated IP soil remained largely mineralogically stable. SEM observations revealed progressive particle agglomeration in both soils and particularly more pronounced at 500 °C. Bulk density decreased significantly with increasing temperature and number of cycles, with cumulative reductions of up to 9.8% for AK soil and 7.6% for IP soil after five cycles at 500 °C. Atterberg limits decreased consistently with thermal cycling, accompanied by a reduction in fines and a corresponding increase in sand-sized particles. Swell potential decreased sharply after the first heating cycle and showed little change thereafter, while collapse potential decreased by more than 50% after initial heating, with no consistent trend in subsequent cycles. Unconfined compressive strength decreased significantly for both soils, with strength loss more pronounced in IP soil (up to 97% at 500 °C) than in AK soil (up to 59%). Overall, the results show that cyclic heating induces irreversible changes in lateritic soils, with the extent and persistence of change controlled by mineral composition, temperature level, and heating history. These findings are relevant to the engineering assessment of soils exposed to high-temperature events such as wildfires and thermal remediation.