Comparative Study On Hot-mix Asphalt Concrete Prepared With Unmodified And Crumb Rubber Modified Bitumen

Due to the unavailability of rail and water transport networks,the strategic connectivity and access,both domestic and cross-border,is dependent on the road network in Nepal.Thus,it is essential that the road network is built and maintained in robust condition.Bitumen is a crucial component of road pavements responsible for the durability and serviceability of the road.Numerous bitumen modifications techniques have been studied and applied around the world in order to improve road performance properties.As several sections of the national highways and urban roads need to be upgraded to asphalt concrete wearing course,modified bitumen which could improve service life of roads would be a boon to an under-developed country with limited budget like Nepal.A lab-scale comparative study of the characteristics of asphalt concrete prepared using commercially available crumb rubber modified bitumen(CRMB-55)with that prepared using conventional unmodified bitumen has been conducted in this study.Among the various types of modified bitumen available,the CRMB was selected because it can be cost effective and environmentally beneficial.Because the crumb rubber modifier is obtained from disposed tyre rubber,the use of CRMB also helps reduce the problem of disposal of waste tyres.All materials and mixture tests were based on the standard specifications published by the Department of Roads,Nepal.The properties of the modified bitumen(CRMB-55)was compared with unmodified viscosity grade bitumen(VG-10 and VG-30)using common laboratory tests.Marshall mix design method was applied for the comparative study of asphalt concrete mixtures prepared using CRMB-55,VG-10 and VG-30 bitumen.The same aggregate type,gradation and other test parameters were used for all mixtures to ensure comparability of the mixes.