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Clay occurrences at Okija, Ubiaja and Iyuku in southern Nigeria were characterized geochemically, mineralogically as well as geotechnically in order to evaluate their industrial potentials. Mineralogical analyses portray kaolinite as the dominant clay mineral with traces of illite in the transported Okija and Ubiaja samples. Geotechnically, the in-situ derived Iyuku clay has distinctive characteristics. It is considerably less plastic, non-expansive, less hydrophilic and of low compressibility due to its lower clay fraction and higher crystallinity of available kaolinites. On the other hand, the Okija and Ubiaja clays are characterized by medium to high plasticity and compressibility. The shrinkage characteristics of the clays as well as their colloidal activities are consistent with their plasticity.Evaluation of the industrial potential of the clays based on their physical, chemical and geotechnical characteristics revealed that they are suitable for the production of refractory bricks and ceramics. Appropriate processing/beneficiation would be mandatory if they are to qualify for other industrial applications, such as rubber, paper, paint and cosmetic industries.

Thirty eight (38) soil samples taken from locations accessible to the BeninOluku -Ifon -Uzebba -Afuze -Auchi -Ukpilla -Okene highway, covering a distance of approximately 185 kilometres and an area of about 12,000 square kilometers were subjected to chemical and mineralogical analyses with a view to determining the variability of their fertility status within the rainforest and savannah vegetational zones. Results show that the soils of the area consist predominantly of quartz, kaolinite, feldspar and sesquioxides of aluminium and iron, including goethite. They are generally acidic with very low cation retention and buffering capacities. Higher concentrations of the major oxides MgO, CaO and K 2 O were recorded in soils of the savannah zone while the soils of the rainforest zone are relatively deficient in these oxides. A chemical productivity index (CPI) of MgO + CaO + K 2 O/Al 2 O 3 is proposed for the soils of the area of study. @ JASEM http://dx.doi.org/10.4314/jasem.v17i3.6

Geotechnical tests were carried out on a total of six samples of red tropical soils developed over sedimentary and Basement terrains, made up of three soils and three termite hills samples. The soil samples were subjected to geotechnical analyses which included the Particle size analysis, Specific Gravity, Atterberg Limits and Compaction Test to evaluate their suitability for road construction. The results from the analyses showed that soils were well graded(GW) with percentage fines ranging from 28.06 to 57.8%, Specific Gravity ranged from 2.40-2.60, Liquid Limit from 36-48.5% , Plastic Limit ranged from 19-30% , Plasticity Index 15-19% and California Bearing Ratio(unsoaked) from 11-24%. For the termite soils Liquid Limit varies from 26.5-33%, Plastic Limit 19-23%, Plasticity Index 10-12% and California Bearing Ratio 24-40%. The Compaction Test results showed that the Maximum Dry Density (MDD) ranged from 1.44 to 1.65%, 1.6-1.8% and Optimum Moisture Content from 16.3 to 23.8% and 12.5 to 17.8% for soils and termite hill respectively. From the results of the analyses and in accordance with the Federal Ministry of Works and Housing, recommendations for road base, subbase and subgrade, both soils can be used for road construction as subgrade but the termite hill of Igarra indicate a better material because of its higher strength with higher MDD to low moisture content.

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