Physical properties of subgrade soils from Nigerian highway master test section 1 (Kano-Kaduna region)

Subgrade materials from Master Test Section (MTS) 1 were tested to obtain their physical properties. Three samples each from the MTSs making a total eighteen (18) samples were obtained and subjected to laboratory test to determine their basic physical properties. Testing include particle size distribution, Atterberg limits and specific gravity tests. The samples were classified according to American Association of State Highway and Transportation Officials (AASHTO) and the Unified Soil Classification System (USCS). The AASHTO soil classification shows that the subgrade soil samples obtained from the MTS 1 were either clayey soil (A-6 and A-7-6) or silty soils (A-4, A-5 and A-2-4). The AASHTO soil classification generally showed that the subgrade samples were “Fair to Poor” in subgrade properties for use as construction materials. The USCS soil classification indicated that most of the samples were lean clay soil with gravel (CL) except few that were either clayey gravel (GC) or clayey sand (SC). This showed that the subgrade samples were mostly clay soil.