LABORATORY STUDY OF LOW COST BITUMINOUS WEARING COURSES

Abstract

Skid Resistance and rutting are two important aspects of low cost bituminous wearing courses like Premix Carpet with Sand/Liquid Seal Coat, Mix Seal Surfacing Types `A' and `B' and Surface Dressing. The effect of wearing out of the surfaces on the skid resistance is normally checked by the PSV of the aggregates used in the surface. In this laboratory study, an effort is made to assess the skid resistance of these surfaces using the British Portable Skid Resistance Tester and also to find out the effect of wearing out of the surfaces on the skid resistance as a whole by designing and fabricating an indigenous equipment which can directly provide the wheel passes over the sample prepared of the surface being tested. In addition to this, the rut depth after a given number of wheel passes is also studied to assess the resistance to rutting of the surface being tested. . While carrying out the wheel passes, the experiment has been carried out both by iron wheel and rubber tyre wheel. Also, while preparing the sample, the specifications of rural roads given by the Ministry of Rural Development have been taken. As a further variation, another sample for each surface with 10% extra bitumen has also been prepared and tested by using the rubber tyre wheel. After the study, it has been established that the Premix Carpet with Sand Seal Coat is the best surface for skid resistance after 100,000 wheel passes. The values are further improved by addition of 10% extra bitumen in the mix. As far as resistance to rutting is concerned, Mix Seal Surfacing Type `A' has shown the best resistance to rutting. Here there is no major change in values by addition of extra bitumen. However, the other surfaces have shown improvement by adding extra bitumen,