USE OF LOW GRADE MATERIALS FOR RURAL ROAD CONSTRUCTION IN DESERT AREAS
N. K Bhasin, Scientist
Panchanan Oli, Scientist
Narinder Krishan, Scientist
Jagdish Chander, Scientist
Ashwani Kumar, Junior Scientific Assistant
Central Road Research Institute, New Delhi
Due to non-availability of hard stone within economical distances in desert areas, particularly in Central Rajasthan, road construction has been posing serious problems, especially in rural areas. However, a calcareous material locally known as 'Dhandla' is found in abundance under an overburden of 1.5 to 2.5 metres. Dhandla, being quite soft material, gets completely crushed under the road roller. Moreover, it is quite problematic to compact dhandla with road roller over the non-cohesive desert sand subgrades. As such, it has not found favour with the road construction agencies.
With a view to evolve low-cost specifications for the construction of rural roads using the locally available low grade materials to the maximum possible extent, a study has been undertaken at this Institute. It has been found that the bearing capacity of dhandla was considerably improved when compacted manually and could be effectively used in the lower layer of low-volume roads.
The details of the work carried out on a section of a rural road in Central Rajasthan are presented. The subsequent performance of the test track for a period of 5 years and the economic aspects are also discussed.
1.1 For effective implementation of developmental programmes in the country, providing adequate network of roads in rural areas is, more or less, an essential necessity. The traditional specifications being followed for rural road construction are provision of stone soling or WBM (OS) in the sub-base, followed by a layer of nous surfacing. Due to non-availability of hard stone within economical distances, especially in desert areas, the cost of road construction is abnormally high. It is, therefore, felt that efforts should be made to find the scientific usage of locally available low grade road materials to the maximum possible extent, resulting in considerable economy. Use of low grade road materials to the maximum possible extent, resulting in considerable economy. Use of low grade road materials has, however, not found favour with the construction agencies. The same set of specifications are being adopted for rural road construction in desert areas, as is being followed in other parts of the country.
1.2 It is a common observation in desert areas that on account of the non-cohesive nature of desert sand sub-grade, the sub-base material has the tendency to sink into the subgrade resulting in deformations of various shapes and sizes. These deformations are subsequently reflected in the road surface causing either immobility or hampering the vehicular traffic. It is, there-fore, considered an essential pre-requisite to provide adequate support to the pavement for better performance. This could be achieved either by stabilising the desert sand sub grade with additives or by providing additional thickness in the sub base. Such treatments would result in increased cost of road construction. The Central and Western parts of Rajasthan have, at present, quite thin density of population where the rate of growth in the volume of traffic on rural roads is not expected to rise at a fast rate in the near future. It is quite imperative, therefore, to utilise the locally available road materials to the maximum possible extent.