A total of ten samples of Pre – Cambrian granitic rocks were collected; (one inch and three-quarter inch sizes respectively) from five quarries in southwestern Nigeria for geo - mechanical and petrographic analyses to determine their suitability as construction materials. The aggregates collected were transported to the petrology and geotechnical engineering laboratory of Federal University of Technology Akure, Nigeria, where they were subjected to the following tests: thin section and modal analysis, aggregate crushing value, aggregate impact value, bulk density, specific gravity, flakiness index, porosity, ten percent fines value and water absorption capacity. Results from the petrographic analyses showed the aggregates samples to be biotite-granite, granites and porphyritic- granite based on their modal analysis. The engineering characteristics of the aggregate samples evaluated shows that the Aggregate Crushing Value ranged from 25.5 to 26.0, Aggregate Impact Value ranged from 17.9 to 18.5, Bulk density ranged from 26.77 to 27.43, Specific gravity ranged from 2.66 to 2.68, Flakiness index ranged from 24.9 to 28.3, Porosity ranged from 0.61 to 0.63, Ten percent fines value ranged from 135.30 to 159.46 and water absorption ranged from 0.49 to 0.68. The parameters of the aggregate samples analyzed falls within the acceptable limit set by the American Standard for testing and materials and British standard. The rocks in the study area fall within the Migmatite-Gneiss Quartzite Complex rocks which explains the high strength characteristics of the samples obtained. Therefore, crushed aggregates from Akure and its environs are of good quality and can be used in any engineering construction.

Keywords: Aggregates, strength, durability, engineering properties, Basement Complex,