Abstract:
This research study examines the impact of aggregate skeleton on the performance of hot mix asphalt. Two distinct gradation techniques i.e., Conventional method of gradation and Bailey method of gradation are put into services to design aggregate skeleton for asphalt concrete mixtures. Conventional method of gradation is actually maximum density line method, based on mid line gradation while Bailey method is an in-depth gradation evaluation technique in which the packing and interlocking of aggregate is considered the backbone of the aggregate structure. Pakistan National Highway Authority class B (NHA-B) specification was followed to design both the gradations. Optimum binder content (OBC), volumetric and strength parameters of both types of mixtures were determined according to the standard specifications of Marshall mix design method. On the basis of calculated OBC, Superpave gyratory specimens were prepared at 125 number of gyration for simulating heavy load condition. Performance tests are conducted at two distinct temperatures (25 0C and 40 0C) for determining rut depth, indirect tensile strength and resilient modulus of asphalt concrete mixtures. For this intend Hamburg wheel tracker device (HWTD) and universal testing machine (UTM) is exercised. Results declared that, aggregate skeleton has prominent influence on the behavior of asphalt concrete mixtures. Bailey gradation mixtures disclosed more rut defiant behavior, high indirect tensile strength and resilient modulus than conventional gradation mixtures. Moreover temperature is found the most significant attribute that influence the behavior of asphalt concrete mixtures. Better performance for both types of mixtures is observed at low temperature than at high temperature.
