LABORATORY INVESTIGATIONS ON WET MIX MACADAM

Abstract

India has the third largest road network in the world. More than 98% of the roads are of flexible type. In the present era of liberalization, the Indian economy is expected to grow at much faster rate in the coming years, as compared to the previous records. It is well known fact that road network of a country drives the economic growth of the country. Additional kilometerage of road is still required to be constructed in the country, to be compatible with economic rise. The Highway Engineers are always engaged in inventing newer techniques in the road construction that gives better results than the previous ones, envisaging the drawbacks of previous techniques. A flexible pavement generally comprises of four layers i.e. subgrade, subbase, base and surface course. For subbase and base course construction, the most widely used material around the world is water bound macadam(WBM) for last 200 yrs.. However, limitations of WBM construction have been understood better in last few years.Therefore, effort has always been to overcome these deficiencies by using some improved quality of construction. Wet Mix Macadam (WMM) has started replacing water bound macadam now. In the present study, an attempt has been made to compare structural properties of WBM and WMM mixes. It is found that WMM is a superior quality construction. Its modulus of elasticity is 22.2% higher and life expectancy is 27% more when compared to WBM construction. iii