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

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