Appropriate use of locally available materials in concrete, bituminous surfacings and layerworks for roads in rural areas

Abstract

The use of locally materials in low volume rural roads can result in significant cost savings. However, this is associated with an increased risk of premature distress or failure. A compromise needs to be found between the probability of premature distress or failure (ie increased maintenance costs) and the cost of improving the structural capacity. Although the use of concrete in low volume roads is very limited, the effect of reducing the aggregate quality will be to decrease the strength and durability of the concrete and probably to increase the shrinkage. Bituminous surfacings are currently tightly specified and comparison with other countries indicates that certain areas of relaxation are possible. These are mostly with respect to the grading and aggregate hardness. It is anticipated that the use of modified bitumens with marginal aggregates will result in lower life-cycle costs for surfacing. Detailed analysis of the structural behaviour of pavement layers has shown that current design techniques have some major deficiencies. It has been clearly identified that thin pavement structures which make the maximum use of the in situ and local materials can provide satisfactory performance provided the drainage and construction quality is well controlled