25-08-2017, 09:32 PM
Abstracts: Flexible pavements are widely used despite some doubts regarding their economics under different conditions. Two most important parameters that govern the pavement design are soil sub-grade and traffic loading. The Indian guidelines for the design of flexible pavements use soil sub-grade strength in terms of California Bearing Ratio (CBR) and traffic loading in terms of million standard axles (msa). Therefore, a study was done to convert the traffic load given in msa into ALD and vice-versa. Mathematical models are developed to estimate the ALD from individual vehicle counts. A critical review of bituminous paving mixes used in India in accordance with the current MORTH Specifications (2001)has been made keeping in perspective the fundamentals of mix selection based on their intended functions in differentcourses within the flexible pavement. There is a proliferation of bituminous paving mixes in India. MORTH Specifications broadly provides 4 mixes for basecourses, 6 mixes for binder courses and 4 mixes for wearing courses. Further two grading, each of BM, DBM, SDBC and BCare specified in the MORTH specifications. Too many options for a specific bituminous course have created confusion in mixselection and are mainly responsible to a considerable extent for the poor performance of flexible pavements in India. Acase has been made out on technical grounds to have only 5 dense graded mixes of different nominal maximum aggregate size in the specifications, as is the case in most developed countries of the world.