SUITABILITY OF AFAKA BORROW PIT FOR SUBGRADE AND BASE MATERIALS

Abimiku J., Pogu J.H. and Bala A. B.

Department of Civil Engineering

Kaduna Polytechnic, Kaduna State

E-mail: ubbe.eggon@yahoo.com, joshpogu@yahoo.co.uk, abdullahibala50@gmail.com

Abstract: The Afaka Mando borrow pit in Kaduna metropolis was investigated for its engineering properties with respect to its suitability as subgrade and base materials in road construction. This was achieved by carrying out laboratory tests on the soil samples for engineering properties such as the natural moisture content, specific gravity, sieve analysis, Atterberg limits, compaction and California bearing ratio. Particle size analysis shows that the percentages passing sieve No 200 range from 0.3 to 0.8%.The liquid limit ranges between 17.31 and 29.2%,  plastic limit ranges from 10.56 to 12.43% and the plastic index ranges between 5.6 and 16.77%.The California bearing ratio (unsoaked) ranges from 12.72 to 33.23%.  The Specific gravity ranges between 2.37 and 2.4 which is not good, while the maximum dry density ranges between 1.76 and 1.98g/cm³ with their optimum moisture content ranging from 9.0 to 17.24% while the natural moisture content was 17.25 to 21.38%. From the result, and according to the Federal Ministry of Works and Housing  Specifications for roads, this lateritic material can be used for subgrade because the C.B.R. is not less than 10%  but cannot be used for base course because the C.B.R. is less than 80%. The result also shows that the lateritic samples are classified as silty or clayey gravel sand (A-2-4).