Investigation of the suitability of the borrow pit materials utilized for the construction of 9.5 km ring road three in Uyo local government area

This research is an investigation of the geotechnical engineering properties of the Laterite soils employed for the construction of the 9.5km Ring Road Three in Ukyo Local Government, Akwa Ibom State, Nigeria. Two samples were collected from the borrow-pit at Mokoro Nist, nit Ibim Local Government Area, Akwa Ibom State at depths ranging from 0.5m to 1.5m. The samples were subjected to the following laboratory tests: Particle (grain) size analysis, Atterberg limit test, Compaction test and California bearing ratio (CBR) test. From the above-mentioned laboratory tests, the percentage passing sieve no. 200 (75µm) ranges between 1.4501% and 4.1476%, liquid limits (LL) ranges between 27% and 29%, Plasticity index (PI) ranges between 4.13% and 6.05%, Optimum moisture content (OMC) ranges between 9.82% and 10.42%, Maximum dry density (MDD) ranges between 19.21kN/m3 and 19.33kN/m3 and the CBR (unsoaked) ranges between 61.21% and 61.46%. In accordance with clause 6201 and 6252 of the Federal Ministry of Works and Housing (1997) Specification Requirement, the lateritic soil is considered suitable for sub-base and base course since their percentage passing sieve No. 200, liquid limits, plasticity index are not greater than 35%, 50% and 12% respectively and also MDD is not greater than 20.0kN/m3 recommended. It could also be deduced that the borrow –pit material is suitable for sub-base only since the CBR (unsoaked) is not less than 30% recommended. However, the Lateritic soils have been found to be of A-2-4 based on the AASHTO classification Scheme and hence, they have significant constituent materials of mainly silty or clayey gravel and sand classified as sandy clay according to O’Flaherty. In conclusion, the borrow-pit material deployed will only be adequate and suitable for sub-base and will not be suitable for base course.