Abstract:
Like other sub-Saharan African countries in the tropics, the middle-belt of Ghana has
rolling and mountainous landscapes with road problems usually associated with drainage
and erosion control. Undulating terrains characterised by steep slopes pose road access
challenges. Conventional rural roads wearing course materials such as gravel or single
bituminous seals have proven inadequate to address the issues, especially on steep hill
sections. To address the problem, the Environmentally Optimized Design (EOD) concept
was employed to select resources, including construction materials, to determine the
suitability of optimum road surfacing alternatives for steep slope sections (gradients of
12% or more) of rural roads in Ghana. Subsequently, based on assumptions of nominal
subgrade (CBR=10%) and low traffic volume (<300 vehicles per day), three alternative
derivatives of concrete, bituminous and stone setts/cobbles surfacing were proposed.
Further, a tentative pavement structure design based on Transport Research Laboratory’s
(TRL) estimator for gravel surface design was used to present different road layer
combinations. For construction demonstration and monitoring, the three surfacing
alternatives are to be placed over different road base materials; i.e., lateritic gravel
stabilised with cement, pozzolana, and quarry dust as additives. This paper focuses on
three surfacings on stabilised lateritic base/subbase layer materials. The outcomes of the
study will contribute to the development of construction guidelines and specifications for
rural roads in Ghana, which could serve as a model for other sub-African countries.
