Effect of Reclaimed Asphalt Material on The Compaction and California Bearing Ratio of Lateritic Soil for Pavement Applications
1Ibitoye B.A., 1Onadiran S.O., 2Subair S. O., 1Hassan D. E., 1Fakorede V., 2Azeez R.O., 1Ige J. A.*
1Department of Civil Engineering, Lautech, Ogbomoso, Oyo State, Nigeria.
2Department of Civil Engineering, Kwara State University, Malete Kwara State Nigeria
DOI: 10.36108/laujoces/6202.71.0101
Abstract
Pavement recycling is an effective practical process for conserving the diminishing supply of construction material and reducing the cost of preserving existing pavement networks. This study investigates the effect of grinding and blending Reclaimed Asphaltic Material (RAM) with virgin lateritic soil aggregate to yield a base/sub-base material suitable for pavement construction in Nigeria, and aims to establish the optimum RAM percentage that produces base or sub-base quality material at reduced cost without compromising pavement performance. Two materials were investigated: an untreated lateritic soil (control) obtained from a borrow pit in Ogbomoso North Local Government, and RAM collected from an old pavement in Ogbomoso South Local Government. A total of seven mixtures were prepared, comprising the untreated control and six RAM-treated blends at 5, 10, 15, 20, 25 and 30% RAM by dry weight. Sieve analysis, moisture content, specific gravity, Atterberg limit, compaction and California Bearing Ratio (CBR) tests were carried out on untreated soil sample to determine its suitability for the pavement layers in accordance with BS 812 and BS 1377, while compaction and California Bearing Ratio (CBR) tests were only carried out on the soil sample combined with RAM. Results showed that aggregate blends containing RAM and lateritic soil in soil-to-RAM ratios ranging from 90:10 to 70:30 (i.e., 10-30% RAM by dry weight of the lateritic soil) are suitable for use as sub-base and base course material respectively, with RAM acting mainly as a mechanical blending agent rather than a chemical stabilizer. Addition of RAM increased the maximum dry density from 1.76 to 2.25 g/cm3 before decreasing to 2.22g/cm3 at West African Standard (WAS) compaction and from 1.82 to 2.37 g/cm3 before decreasing to 2.34g/cm3 at AASHTO compaction, while the optimum moisture content showed an overall decreasing trend. Unsoaked CBR increased from 57% to 94% (WAS) before decreasing to 92% and from 72% to 97% (AASHTO) decreasing to 95%, and soaked CBR increased from 18% to 34%(WAS) decreasing to 31%. This study contributes new laboratory evidence, specific to Nigerian lateritic soil, on how RAM dosage affects compaction and bearing-ratio behaviour, and recommends RAM-lateritic soil blending as a cost-effective, sustainable alternative for sub-base and base course pavement construction.
Keywords: Reclaimed asphalt pavement (RAP); lateritic soil; mechanical blending; pavement subbase; base course; compaction; California Bearing Ratio; sustainable pavement materials