Experimental investigation of modified bituminous concrete mix using nitrile butadiene rubber (NBR)

Bitumen is the most widely used constituent in the construction of roads in India, but due to high vehicular traffic and variation of climatic conditions along the length and breadth of the country, the longevity of such road surfaces is always under criticism. The aim of the present study was to explore the possible use of Nitrile Butadiene Rubber as a partial replacement of bitumen in road construction. Characterizations tests on plain bitumen (i.e. VG30) and bitumen blended with NBR were conducted and the change in properties were observed. Bituminous Concrete mix design for marshal stability value to determine the optimum binder content was also navigated. Subsequently, SEM analysis has also been incorporated to check the change in properties of modified binder. A comparative analysis of marshal stability results from virgin blend and modified bitumen mix with varying percentages of NBR (i.e. 5%, 6%, 7% & 8%) was performed. Thereafter, the stripping studies and extraction test for each mix proportion was executed. Based on these results certain conclusions were drawn. It was found that the use of NBR with 6% gave the finest results having higher rut resistance i.e. permanent deformation, of pavement which is principally caused by repetitive deformation due to traffic loading. This study showed that NBR is a promising substitute which can be used commercially in road construction.