Alternative Surfacing for Steep Hill Sections in Ghana – Phase 2

2017

English

Over the past two decades, the provision of all-weather access to rural communities has become apriority of the Department for International Development (DFID) in support of poverty alleviationand the stimulation of economic growth in Africa and other countries. DFID has, therefore, fundedresearch and knowledge transfer projects in developing countries through Research in CommunityAccess Partnership (ReCAP). The outcomes of this successful research include innovative andunconventional approaches that can provide beneficial and cost-effective solutions to improve lowvolume rural roads in the African Community Access Programme (AfCAP) partner countries, throughfor example, the use of alternative road surfacings.The Council for Scientific and Industrial Research (CSIR) in South Africa, in partnership with theBuilding 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 inGhana. The objective of the current study was to provide practical information on the suitability ofalternative road surfacings and paving techniques that are cost-effective and that offer sustainablesolutions for road surfaces on steep gradients (higher-risk road sections). As part of the study, theproject 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 transferredand 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 usedby the DFR. These surfacings will be placed over road base materials, which comprise eithermechanically stabilised lateritic gravel or a mixture of laterite gravels with different additives such aslime, pozzolana and quarry dust. The three surfacings and the two different base layer materialsprovided 18 different combinations of pavement solutions to address problems affecting steepsections of feeder roads in Ghana. In addition, various options of erosion control treatments andalternative drainage structures to kerbs are proposed for the study. The 18 pavement options werescaled 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 keyoptions are recommended for the demonstration sites. These are; (1) 70 mm ultra-thin continuouslyreinforced concrete on 200 mm stabilised laterite base, (2) 50 mm asphalt concrete with processedlateritic gravel and AC-10 bitumen on 200 mm stabilised laterite base, (3) interlocking paving blockson 150 mm stabilised laterite base, and (4) Otta seal [14-25 mm aggregates] on 100 mm stabilisedbase 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 astechnical outputs of this project. The findings and overall outcomes of the study, including theoutcomes 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 finalreport.

Anochie-Boateng, J.; Debrah, E.