Evaluation of Some Lateritic Soils of Basement Complex Rocks From Ado Ekiti and Environs, Southwestern Nigeria for Road Construction

Abstract

Suitable soils for road pavement construction are getting depleted. Highway Engineers are constantly in search of locally-available and suitable soils for construction of pavement layer road. This work investigates the engineering properties of lateritic soil derived from Charnockites, Migmatites, Pegmatitic Schists and Gneisses rocks, in Ekiti State, and were evaluated for their suitability for road construction. Eight (08) soil samples were randomly taken (two each from the four different rock types). They were subjected to geotechnical analyses which included particle size analyses, specific gravity, Atterberg limits, compaction, and California bearing ratio (CBR) tests. Values obtained were compared with Federal Ministry of Work Standard and Specification. Results of the study show that lateritic soil derived from Charnockitic rock have percentage fines ranging from 26.9-28.6%, Specific Gravity: 2.52-2.57, Liquid Limit (LL): 26.35-26.5, Plasticity Index (PI): 8.57-11.81%, Maximum Dry Density (MDD): 2.09-2.12 and CBR value (soaked): 17.2-29.2%; Migmatite had percentage fines varying from 43.1 to 45.5 %, Specific Gravity: 2.52 2.57, LL: 28.3-47.5%, PI: 13.88-23.36%, MDD: 1.67-1.77 and CBR (soaked) 7.8-13.8%; Pegmatitic Schist also had percentage fines varying from 36.49-56.74%, Specific Gravity ranged from 2.44-2.53, LL: 45.5-46.6, PI: 17.44 19.3%, MDD 1.59-1.67 and CBR (soaked) from 8.2-14.1%; Gneiss showed percentage fines varies from 28.1 to 45.1%, Specific Gravity: 2.5-2.55, LL from 29.2-40.01, Plasticity Index 8.16-18.97%, MDD 1.73-1.96 and CBR (soaked) from 17.1-25.2%. Comparison of the results with the standard specifications of Federal Ministry of Works for pavement materials: LL <36, PL ≤12, % fines < 30, CBR (soaked) >30 %, and MDD ≥2 shows that only the lateritic soils derived from Charnockitic rock obtained at Ado-Ekiti and Ikere-Ekiti satisfy every aspect of the geotechnical properties except CBR values (test results less than the standard). Although they have the highest values compared with soils derived from others. Lateritic soils derived from Migmatitic rock, Pegmatitic Schist, and Gneissic rock do not satisfy all plasticity and strength properties requirements (values of LL < 36%, PI ≤ 12 %, % fines < 30%, and MMD ≥2). They are therefore likely to deteriorate faster than soils derived from Charnockitic rock.

Publication Info:

Author: Akujieze, C. N. and Ogunlade S.O.

Volume: 56

Issue: March

Published By: Journal of Mining and Geology, 2024-03-01