Active Soils of the Niger Delta in Road Pavement Design and Construction |
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Authors: | Olujide Omotosho Amadise Save Ogboin |
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Institution: | (1) Civil and Environmental Engineering Department, University of Port Harcourt, Port Harcourt, Nigeria;(2) Amaogbo Oil Services Ltd., 75, Tombia Street, GRA (Phase II), Port Harcourt, Nigeria |
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Abstract: | Active soils existing to irreplaceable extents (both laterally and vertically) within the freshwater zone of the Niger delta
are known and have been shown to be highly undesirable in their natural forms for road construction. This is because they
swell extensively in the rainy season and shrink proportionately in the dry months together with any structure including road
pavement constructed with or placed on them. In this paper, four samples of these soils collected from across the Niger delta
were subjected to chemical stabilization with slaked-lime and calcium chloride (CaCl2) to reduce swelling potential while resulting mixtures (corresponding to tolerable swelling limits) were stabilized with
Portland cement to improve strength. First, swell indicator (i.e. 24-h free swell index) was found to diminish with increasing
stabilizer content while for combined plot (independent of location/percentage fines), about 10.7% and 6% slaked-lime and
CaCl2 were found to be required to achieve the minimum (2.5% free swell) tolerable, normal or non-swell soil condition. Under this
condition and for individual soil materials, addition of cement was found to enhance continual increase in MDD, soaked-CBR
and durability index such that the soil becomes better compactible, stronger and more durable with increasing cement content.
About 2.6% and 14.6% cement contents were found needed to respectively produce sub-base and base-course materials in roadworks
with the latter much more durable than the former. The graphs so obtain could also constitute a complete graphical model for
preparing deltaic active soils for use as road pavement materials. |
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Keywords: | Montmorillonite Active soils Slaked-lime Calcium chloride CBR Durability |
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