Laboratory Evaluation of Rutting Performance of Asphalt Concrete Mixtures by Crumb rubber modification [ ]

One of the most important distresses in flexible pavements is Permanent deformation (rutting). It is a severe problem mostly in those countries having high temperature like Pakistan. Asphalt Rubber (AR) is produced by mixing crumb rubber that is obtained from waste tires with asphalt binder. Mixtures produced with asphalt rubber are one of the substitutes to reduce permanent deformation. It is also one of the most suitable applications to dispose the waste tires. In this study our aim is to compare the rutting behavior of asphalt rubber mixtures with the conventional mixtures. For this study, two aggregate gradations, namely NHA class "A" and NHA class "B" were chosen. Wet process of mixing was used to produce asphalt rubber and Marshall Mix design was used to determine optimum asphalt rubber content. Uniaxial repeated load test (cyclic creep test) and Wheel Tracking Test (WTT) were performed to study the rutting performance of asphalt mixtures. During uniaxial repeated test, temperature was set to 25, 40 and 55 ⁰C and specimens were tested for a period of 3600 cycles. Stress levels of 100, 300 and 500 kPa were used. Pulse period was selected 2 second and the pulse width was selected 0.5 second. Wheel tracker test was conducted for a period of 10,000 load cycles at three different temperatures 25, 40, and 55 ⁰C. The testing results of this study confirmed that the use of asphalt rubber to prepared asphalt mixtures increases significantly the resistance to permanent deformation (rutting). This study also concluded that crumb rubber modified bitumen is more effective for coarser aggregate gradation than finer aggregate gradation to increase permanent deformation resistance (rutting resistance).