Petrographic and Geochemical Studies of Lateritic soils in Kwara State Polytechnic Ilorin

Abstract

Petrographic and geochemical studies of lateritic soil have been examined in order to determine their suitability for construction purpose. Ten lateritic soils were examined through petrographic studies and X - ray fluorescence to ascertain their suitability for industrial applications. Petrographic studies suggest that the laterites are mostly associated with specific landforms such as mounds and terraces formed through long period of weathering processes and derived from underlying bedrock which often leads to the development of terraces or mounds characterized by small to large-sized nodules or concretions which exhibit varying degrees of hardness and cementation depending on the minerals and chemical constituents distributed throughout the soil matrix. The chemical analysis from X – ray fluorescence of the lateritic soil suggest SiO2, Al2O3, Fe2O3, K2O, Na2O, TiO2, CaO and MnO. The results agree with petrographic studies which indicate that SiO2, Al2O3, and Fe2O3 are the dominant phases in both the parent rock and its derived products. SiO2 suggest enrichment in the soil while the proportion of alumina (Al2O3) reflects the presence of aluminosilicates and its enrichment which can be attributed to the weathering alteration of feldspar to clay mineral, causing leaching of Al2O3 by infiltrating acid rain/recharge water into the ground. K2O, Na2O, MgO, CaO and P2O5 are decreasing due to leaching of the soil. TiO2 also increases in all the soil samples and it contribute to the soil reddish – brown colour which are mostly formed through weathering of silicate minerals. However, lateritic soil remains one of the best natural materials used in compressed earth bricks because it is a well graded soil that combines both cohesive and cohensionless parts of the soil. It also contains sesquioxides and clay minerals which are very useful in natural binding process as well as in the presence of most chemical binders. Increase in ratio of SiO2 to Al2O3 leads to chemical reactivity known as geopolymerization in the presence of amorphous materials. This enhancement reactivity supports its usage in geopolymer synthesis and as a suitable precursor for geopolymer production.

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