INVESTIGATION ON OPTIMAL USE OF GRAVEL IN FLEXIBLE PAVEMENTS

Abstract

Gravels in India are available in large quantities in many places such as stream bottoms or terraces adjacent to streams, outwash plains and fans adjacent to mountains. Aggregates form the major portion of the pavement structure and it is the prime material used in pavement construction. Aggregates primarily bear the stresses and have to resist wear due to abrasive action of traffic. Due care should be given in the proper selection of the aggregates. Although hard aggregates are found almost all over India, but these are scarce at certain places like Indo-Gangetic planes. Similarly soft aggregates occur at all places in India, while these aggregates have low crushing and abrasion value than the hard aggregates. In the present study, attempts have been made to review the various types of aggregates and their properties including soft aggregates. Gravel has been used in base course for road construction instead of conventional crushed aggregates. Various tests such as combined flaky and elongation indices, angularity number, density test, CBR test and shear test (using large shear box) have been conducted for judging suitability of the aggregates. Plate load test on different pavement models using gravel and gravel-crushed aggregate mixture have also been conducted. It has been found that gravel can be used successfully in road construction instead of crushed aggregates. The economic analysis shows that cost of pavement material is much less for the mix of 70% gravel and 30% crushed aggregates, in comparison to that of crushed aggregates. Further the use of gravel will be much more economical if it is found locally. It has been recommended that vast potentials offered by gravel should be fully exploited for the construction of base course in the flexible pavements.