The role of rejuvenating agents in cold recycled foam asphalt mixes

Cold-in-place asphalt recycling is one of the most commonly used methods of pavement rehabilitation. Using rejuvenating agents can activate the RAP binders and improve performance of cold recycled mixtures. In this study, waste cooking oil (WCO) and a combination of waste cooking oil and a soft asphalt binder (WCOSB) were used to recycle mixtures containing different amounts of Recycling Asphalt Pavement (RAP) materials. The WCOSB rejuvenator was mixed with cold RAP materials in different methods in order to investigate the effectiveness of the rejuvenating agents in recycled mixtures. Modified Lottman, Hamburg wheel tracking, four-point bending beam fatigue, and semi-circular bending fracture tests were conducted on the mixtures. Performance of WCOSB was better than that of WCO against moisture sensitivity. It was shown that WCO weakened the cohesiveness of the asphalt binder and reduced moisture resistance of the asphalt mixtures. Therefore, this material cannot be considered as an effective rejuvenating agent despite its positive rutting performance and cracking resistance in recycled mixes. Investigating the method of application of the rejuvenating agent, it was found that addition of the rejuvenator to RAP materials resulted in better cracking and moisture resistance of the recycled mixtures. This is despite its adverse effect of increasing rutting susceptibility of the recycled mixtures.