ABSTRACT:
The economic importance of laterites as a road-building material and their other structural uses, together with their varied properties which depend on very many factors, have made the study of laterites a subject of continuing interest. This paper traces the geological origins of some Eastern-Nigeria laterites, gives their genetic classification based on their silica/sesquioxide ratio, outlines their physiochemical and chemical properties and seeks some relations between the iron-oxide content, the specific gravity, the sesquioxide content and the other physical and engineering properties of the samples. An attempt is made to rank the laterites with D’Hoore’s specifications.Since the properties of laterites are dependent on the type of pretreatment given to the samples, fresh and four-year-old samples were tested after being subjected to varying degrees of drying. The engineering and physical properties tested included the specific gravity of samples divided into particle size-groups, the Atterberg limits, the linear shrinkage, the dry density-moisture content relations, the CBR-moisture content relations and, for coarse particles of the samples, the aggregate tests of moisture absorption, the aggregate crushing value, ‘10%’ fines, flakiness test and elongation-index tests.The conclusion reached is that, while the results agree broadly with those obtained previously, no correlation was found between iron-oxide content and any other physical or engineering properties as has been suggested by others. However, the results suggest that there is some relation between the sesquioxide content and other physical and engineering properties. The strength properties as determined by the CBR tests give high results for most of the samples.
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