Abstract:
Rutting is a common distress occurring in flexible pavements, mainly due to the gathering of permanent deformation in any or all of the layers in flexible pavement. The amassing of perpetual twisting in the black-top layers is presently perceived to be real reason of rutting in the flexible pavements. In Pakistan, this is an outcome of expanded tire weights and over loading, which subjects the black-top surfacing layer closest to the tire-asphalt contact zone to expanded burdens. Along these lines the investigation of change in perpetual twisting properties of black-top blends by adding modifiers to bitumen has turned into the center of examination, which expects to relieve or lessen rutting in flexible pavements. This study aims to evaluate the execution of asphalt mixtures modified with crumb rubber through resilient modulus, wheel tracker and dynamic modulus test. The research methodology incorporates two phase approach (1) Laboratory Prepared asphalt mixtures (2) Plant produced asphalt mixtures. Bitumen penetration grade of NRL 60/70 and an aggregate source of Margalla quarry were used for preparation of mixtures. The overall findings revealed that with the modification of crumb rubber the asphalt mixtures rutting resistance potential significantly increases and also there is an expansion in resilient modulus and dynamic modulus. With modification of 7% crumb rubber the rut depth was reduced to be 33% for asphalt mixtures of lab prepared and 22% for asphalt mixtures of plant produced. Likewise the percentage increase in resilient modulus for rubber modified mixtures were found to be 44% and 36% at 25 and 40oC for lab prepared asphalt mixtures, 42% and 31% improvement was noted for plant produced asphalt mixtures. Statistical analysis was done on dynamic modulus results and the findings showed frequency as the most critical factor which has a significant effect on the dynamic modulus of asphalt mixtures followed by temperature and rubber content.
