Free Swelling and Modulus of Elasticity of Compacted Black Cotton Soil Treated with Reclaimed Asphalt Pavement

Abstract

Black Cotton Soil (BCS), collected from Numan, in north-eastern region of Nigeria was stabilized with Reclaimed Asphalt Pavement (RAP), collected from failed road surface, along Minna-Bida road in Niger state Nigeria. The BCS was replaced with RAP at 0%, 10%, 20%, to 100% by weight of the soil. X-ray diffraction test on the BCS revealed predominantly, presence of quartz, microcline, albite and kaolinite, while that of RAP shows quartz, albite, orthoclase, phylogopite and actinolite. Maximum Dry Density (MDD) of the mixtures increased from 1890kg/m3 at 0% RAP content to maximum value of 2036kg/m3 at 30% RAP, after which the value reduced to 1925kg/m3 at 100% RAP. Scanning Electron Microscopy showed fewer cracks in mixture with 20 and 30% RAP contents, rather an interlocking of particles of different sizes in a very dense state was revealed. Unconfined Compressive Strength (UCS) increased from 392kN/m2 at 0% RAP to 947kN/m2 at 30% RAP content, representing 58.6% increase. The values, thereafter, reduced to 17.5kN/m2 at 100% RAP content. Modulus of Elasticity increased from 10.4Mpa at 0% RAP to 42.5MPa at 30% RAP, representing 75.5% increase. The values, thereafter, reduced to 2.9MPa at 100% RAP content. The swelling potential of the mixtures reduced from medium at 0% RAP content to low at 30% RAP content.