Geology and engineering properties of laterites from Ilorin, Nigeria

Twelve samples of Nigerian laterites were obtained from Ilorin, a rapidly growing urban center, and capital of Kwara State, Nigeria. Three varieties of laterites (clay, gravel and crust) were identified and subjected to mineralogical, chemical and geotechnical analyses which included: identification of clay and non-clay minerals by X-ray diffraction (XRD) techniques; chemical composition by X-ray fluorescence spectrometer analysis; pH of soil in water; moisture contents and specific gravity determinations, grain size analysis; compaction test by Harvard Compaction Apparatus and unconfined compressive strength determination. The laterite soil samples are composed of kaolinite and illite clay minerals with some quartz and feldspar. They were found to be rich in SiO2 (\u3e 45%) Fe2O3, (\u3e 16%) and Al203 (\u3e 10%). These soils yielded maximum strength when compacted on the dry side of their optimum moisture content (OMC). The soils are not expected to perform very well as concrete aggregates since they contain high amounts of SiO2 and Fe2O3. These oxides are known to have deleterious effects on construction materials, particularly concrete aggregates. © 1983