Labour-based surfacing trials on the Mozambique Feeder Road Project

Spot improvements to earth and gravel roads in Developing Countries to maintain all weather access may be most cost-effectively carried out using labour-based techniques. In 2000 TRL Limited were commissioned by the Department for International Development to provide technical assistance to the Mozambique Feeder Roads Project. A range of bituminous surfacings were developed and tested that may be applied to gravel roads using labour-based construction techniques. The bituminous surfacings were: single and double sand seals; gravel-bitumen seals; single and double surface dressings; pre-mixed bitumen and gravel; and penetration macadam. Three sources of aggregates were tested: a natural gravel; selected sizes of hand-knapped rock; and fine sand. The construction of the trial sections and their surface dressing are described. The performance of each of the surfacing applications was evaluated using a visual condition survey in March 2005, 3.5 years after construction. The single sand seal was the least successful and required replacing. The best results were obtained with penetration macadam followed by pre-mixed bitumen and gravel but these were the most expensive treatments. The single surface dressing was considered the most economical application.