Yaw A. Tuffour^1,, Samuel Y. Banini², Charles A. Adams¹

Road construction projects in the Afram Plains area in Ghana are characterised by high material haulage cost due to the unavailability of suitable geologic materials local to the area for road work and the need to haul from distant sources. This study investigated the suitability of rock-like shale local to the Plains for road construction in the area. Samples of the rock-like shale from the Plains were evaluated in terms of strength as coarse aggregates and as compacted material before and after being subjected to soaking as well as varying cycles of soaking and drying. The soaking and drying simulated conditions under which pavement structures exist in the area over their design life due to the heavy rainfall in the Plains and the poor drainage characteristics of the terrain. The results indicated that whereas the rock-like shale in the un-soaked state met all the Ministry of Roads and Highways strength specifications for road aggregates, it lost practically all its strength in the soaked state. Water absorption was 900% the specification upper limit. Compacted samples lost close to 90% in CBR value following four days soaking. The high loss in strength under wetting conditions and the material’s ability to imbibe large amounts of water do not favour the use of the Afram shale for road construction in the long-term, given the fact that there are ample opportunities, within the area, for the material to come into contact with water for a long time when existing as part of a pavement structure.

Afram Plains, poor drainage, road construction, strength, rock-like shale, wetting and drying cycles