Economic viability of asphalt pavement: surface recycling in Urban areas of Tanzania.

Relying solely on the standard highway construction and maintenance specifications and methods costs Tanzania considerably, both economically and environmentally. Researching and carrying out other viable alternatives e.g pavement recycling can alleviate Tanzania from this problem.. For example, study on the reuse of some of the old pavement surface materials in resurfacing works in urban areas of Tanzania was carried out on Mandela Road in Dar es Salaam. In this study, several reclaimed asphalt pavement (RAP) surface samples were cored randomly on the selected stretch along the research road. Various relevant laboratory tests were performed on these samples and the new materials (aggregates and asphalt cement) selected to be used in the study. These tests were necessary to determine the deficiencies present in RAP and to select the new materials to be added to achieve the required specifications (mix-design). Mix designs were also carried out for conventional overlays with new materials. Designed mixes, both recycled and conventional, were then tested for their mechanical properties (Marshall criteria). Results from these tests showed that recycled mixes were comparable to the conventional ones. Hence, their field performance could be expected to be similar in both cases. Based on the mix-designs achieved above, resurfacing costs, for both alternatives were finally determined, analysed and compared. Results from this analysis revealed that, reuse of old asphalt pavement surface materials in resurfacing works in urban roads of Tanzania can have cost savings of up to 12 % and 26 % by recycling with 20 % and 40 % RAP respectively. Dar es Salaam City has a road network of 1150km of which about 300 km are paved [Japanese International Cooperation Agency et al (1995)]. Assuming a ten year programme for resurfacing the paved roads by hot-mix recycling at 30km per year, a total amount of 177m3 and 430m3 of asphalt cement can be conserved for 20% and 40% RAP respectively, saving the City about US$ 72,000 and US$ 174,000 in foreign currency annually. Construction aggregates, amounting to 4,800m3 and 9,600m3, costing about Tshs.107 million and Tshs. 214 million for 20% and 40% RAP respectively can also be saved. Patchwork costs (Tsh.214 million annually), necessary in case of conventional overlays are also eliminated in this method. Provided that long term performance of recycled roads are comparable to the conventional overlays, hot-mix surface recycling can be a viable alternative in urban areas of Tanzania.