Low-Temperature Fracture Characteristics of Reclaimed Asphalt Pavement Modified with crumb rubber and rejuvenator

Recycling and reusing materials have received much attention from researchers in recent decades. Today, environmental issues have become very important due to the limitation of available resources as well as the increase in the cost of new materials. Since most of the existing roads in Iran have flexible pavements, using reclaimed asphalt pavement (RAP) and using fewer new materials can be considered an environmentally friendly solution. In recycling asphalt pavements, there is a major concern related to low-temperature cracking. The purpose of this research is to investigate the low-temperature cracking properties of asphalt mixtures containing RAP along with other additives to introduce a mixture with performance characteristics equivalent to the new asphalt mixture. For this purpose, asphalt mixtures with two different contents of RAP (25% and 50%) were considered. Also, to improve their adhesion properties, the addition of a rejuvenator (10% by weight of RAP binder as the optimal percentage) and to improve the resistance of the mixture against cracking, crumb rubber (10% by weight of new binder) was considered. An indirect tensile strength test and a semi-circular bending test (SCB) were performed to investigate the properties of the mixtures. Also, the crack mouth opening displacement (CMOD) during the SCB test was measured through imaging. According to the SCB test, adding RAP to the base sample reduces the fracture energy. But adding rejuvenator and crumb rubber to the recycled samples improves the properties of the mixture against crack growth. The results showed that the asphalt mixtures containing RAP and additives, according to the tests used in this research, presented equal or even better performance than the new asphalt mixture. Also, the combined index of fracture energy - CMOD can be used as a suitable criterion to investigate the effect of RAP, rejuvenator and crumb rubber in asphalt mixture.