CLOSE GRADED COLD MIX FOR CONSTRUCTION AND MAINTENANCE OF RURAL ROADS (Paper 838)

Rural Roads connectivity promotes access to economic and social service and thereby increases agricultural income and employment opportunity in rural areas. Construction of good quality, all weather rural roads is the focus of rural road development programs in India. Therefore, development of cost effective and environment friendly materials is the aim of researchers. Closely graded Premix Carpet popularly known as mix seal surfacing containing graded aggregate and hot melted paving bitumen is a cost effective wearing coat specification used in India. The thickness of this specification is restricted to 20 mm with two different grading for low and high rainfall areas. Hot mixed closely graded premix is prepared and laid at fairly high temperature requiring high energy input and lead to higher carbon footprint. Therefore, a laboratory investigation was undertaken to develop and design cold mix containing tailor made bitumen emulsion as a cold mix binder and closely graded mineral aggregate. This new specification has advantages over available specifications of close mixed open graded premix with seal coat as it does not need seal coat. A mix design procedure has been developed based upon Indirect Tensile Strength values. Here, the heating process is completely eliminated and use of existing hot mix plant is encouraged through a conversion kit installed along with heat tracing tap to eliminate completely heating and burning which also increases work progress by more than 2 times.
In current practice, Bitumen Emulsion based cold mixes are being used in the application of Open Graded Premix Carpeting (OGPC) and Seal Coat, 20 mm thick in rural road sector which is difficult to continue the construction and has the challengesto work with varied quality of aggregates available at different sites, different climatic condition, lack of proper chemical combination in bitumen emulsion, need of pre-wetting of aggregate before mix production, not to able to utilize existing hot mix equipment in the operation, high cost in construction for very low progress of work etc. To overcome all these challenges, Close Graded Premix Carpeting (CGPC) may stand complete replacement of conventional Bitumen Emulsion based Cold Mixes (OGPC-SC) for its different types of advantages and benefit as mentioned below.