Comparative Studies on Performance of Bituminous Mixes Containing Laboratory Developed Hard Grade Bitumen

Bitumen is used as binder for production of bituminous mixes for road construction. Bituminous pavements are used in over 95 % of roads in India for highways, district roads, among other types. Hot mix asphalt (HMA) technology is widely adopted in India for the construction of bituminous pavements. The main concern of a pavement designer is the durability of the bituminous mixes during the design life because the changes in temperature and traffic loadings during the life of the pavement put significant stress on the pavements, thereby producing various kinds of distresses, and finally leading to premature road failure. Therefore, with prevailing mixed traffic conditions, from passenger cars to heavily loaded trucks, on Indian roads, pavement design with conventional materials is a challenge. With the current trend toward developing mechanistic flexible pavement design and the need for more reliable design procedures, accurate characterization of HMA properties is needed. The current Indian pavement design guidelines recommend the use of VG-40 grade bitumen for pavement designs carrying more than 30 million standard axle repetitions in traffic. However, the production of VG-40 by Indian refineries cannot keep pace with the demand of VG-40 for road construction. So, the main objective of this study was to develop harder-grade bitumen by a new process to meet the requirement of the highway profession. The modifiers used in the study are gilsonite and high-density polyethylene homopolymer. Furthermore, the comparative study of the performance evaluation of the laboratory-developed and conventional VG-40 bitumen has been reported in this study. This article also presents example of flexible pavement design as per IRC:37-2012, Guidelines for the Design of Flexible Pavements (Third Revision). Based on the analysis, it is concluded that the thickness of the dense bituminous macadam layer may be reduced by using newly developed bitumen as opposed to the conventional VG-40 bitumen. This reduction in the overall pavement thickness would result in huge savings of both materials and money.