Alternative surfacing for steep hill sections in Ghana: Phase 1. Final Report

2016

English

Over the past two decades, the provision of all-weather access to rural communities has become a priority of the Department for International Development (DFID) in support of poverty alleviation and the stimulation of economic growth in Africa and other countries. DFID has, therefore, funded research and knowledge transfer projects in developing countries through Research in Community Access Partnership (ReCAP). The outcomes of this successful research include innovative and unconventional approaches that can provide beneficial and cost-effective solutions to improve low-volume rural roads in the African Community Access Programme (AfCAP) partner countries, through for example, the use of alternative road surfacings. The Council for Scientific and Industrial Research (CSIR) in South Africa, in partnership with the Building and Road Research Institute (BRRI) of Ghana, was appointed by Cardno Emerging Markets (UK) Ltd to undertake Phase I of a two-phase study on alternative surfacing for steep slopes in Ghana. The objective of the current study was to provide practical information on the suitability of alternative road surfacings and paving techniques that are cost-effective and that offer sustainable solutions for road surfaces on steep gradients (higher-risk road sections). As part of the study, the project team engaged fully with assigned counterpart staff within the Department of Feeder Roads (DFR) of Ghana to ensure that the knowledge acquired in the course of the project was transferred and entrenched within the DFR. A major outcome of the project is a matrix of three alternative surfacing options (i.e. concrete, bituminous and stone setts/cobbles) for comparison with the gravel wearing courses currently used by the DFR. These surfacings will be placed over road base materials, which comprise either mechanically stabilised lateritic gravel or a mixture of laterite gravels with different additives such as lime, pozzolana and quarry dust. The three surfacings and the two different base layer materials provided 18 different combinations of pavement solutions to address problems affecting steep sections of feeder roads in Ghana. In addition, various options of erosion control treatments and alternative drainage structures to kerbs are proposed for the study. The 18 pavement options were scaled down to six key options that were ranked for the demonstration sections to be designed, constructed and monitored under the Phase II project. Under limited budget condition, four key options are recommended for the demonstration sites. These are; (1) 70 mm ultra-thin continuously reinforced concrete on 200 mm stabilised laterite base, (2) 50 mm asphalt concrete with processed lateritic gravel and AC-10 bitumen on 200 mm stabilised laterite base, (3) interlocking paving blocks on 150 mm stabilised laterite base, and (4) Otta seal [14-25 mm aggregates] on 100 mm stabilised base and 150 mm stabilised subbase. This is the final report on the work carried out under Phase I of the project. Three separate reports (i.e. an inception report, a draft report, and a workshop report) have been submitted to the client as technical outputs of this project. The findings and overall outcomes of the study, including the outcomes of the inception study, detailed study, workshop, and feedback from the DFR and AfCAP, as well as recommendations and scoping for Phase II of the study are incorporated into this final report.

Anochie-Boateng, J.; Debrah, E. K.