THE ROLE OF BORROW-PIT MATERIALS IN SUSTAINABLE ROAD CONSTRUCTION: INSIGHTS FROM BONNY

Abstract

The primary use of soils in engineering projects such as roads, buildings, railways, dams and others structures necessitate assessing their index and mechanical properties. This study focusses on identifying the optimal materials for road construction and exploring options for managing ineffective waste generated on site. The materials are categorized based on their index and mechanical properties. Six different points of soil samples were collected at different points, ranging from 1.0 to 3.0 meters deep. The collected soils samples underwent various laboratory tests: Sieve Analysis, Compaction Test, California Bearing Ratio (CBR), and Specific Gravity (SG). Particle size distribution analysis indicated the sample’s fine grading, with less than 15% passing through sieve No. 200 (0.075mm) measuring 0.04%, 0.14%, 0.31%, 0.08%, 0.01%, and 0.18%. The average Natural Moisture Content (NMC) of the six (6) sample collected was found to be 13.88%. Maximum Dry Density (MDD) and Optimum Moisture Content (OMC) of the first point were determined as 2.20g/cm^3 and 14.00%, and the remaining five (5) points were (2.20g/cm^3 and 13.50%, 2.21g/cm^3 and 12.50%, 2.08g/cm^3 and 13.00%, 2.06g/cm^3 and 12.25%, and 2.04g/cm^3/13.40%) respectively. The California Bearing Ratio (CBR) results after soaking for the six (6) samples were 25.70%, 24.50%, 22.3%, 21.7%, 20.40% and 23.40% respectively. Specific Gravity (SG) Ranged from 2.67 to 2.96kg/m^3, classified according to American Association of State Highway and Transportation Officials (AASHTO). Materials were categorized into A-1 with subgroups A-1a and A-1-b, constituting 50% 29.1% respectively, indicating predominantly stone fragments and sand. Overall, the subgrade samples were deemed excellent too good for road construction purposes.