Engineering geological Characterization of Basement Rocks for Construction Aggregates: A Case Study of Kajuru Area Kaduna, Nigeria.

Abstract

The microstructure, mineralogical composition and analysis of chemical constituent of rock samples were evaluated as part of the research on the quality and suitability of rocks in Kajuru, Kaduna State, Nigeria as sources of aggregate for construction. Advanced Spaceborne Thermal Emission and Reflection (ASTER) Global Digital Elevation Model (GDEM) in Global mapper software was used to visualize three dimensional perspectives (3D) of the study area and quantities of major oxides present in Rock samples were determined using x-ray florescence machine called X-supreme 8000. The microstructural characteristics of rocks such as mineralogy, structure, textural and distributions of minerals in the matrix were studied using a petrographic microscope. The rock predominantly consists of porphyritic granites and gneisses with minor quartz vein and quartzofeldpathic pegmatite intrusions. The high silica contents are confirmed from microscopic studies that elucidated the prevalent mineral specie to be felsic component - quartz and feldspar with interlocking grain boundary. The studies revealed mica, microcrack and fracture in some of the rock type which will invariably affect their engineering performance. It is therefore recommended that physicomechanical evaluation be carried out on the rock aggregates to establish the strength of aggregate and the link between physicomechanical properties and geological characteristics of the rock.

Keywords: Basement rocks; microstructure; mineralogical composition; petrography