Effect of RAP and glass fiber on mode I fracture behaviors of ultra-thin friction course

•Effect of RAP and glass fiber on fracture behaviors of UTFC were investigated.•The size-independent fracture energy was obtained considering the tail part of the load–displacement curve.•Two new parameters, cracking resistance index and balanced cracking index, were adopted to characterize the fracture performance. Ultra-thin friction course (UTFC) presents excellent performance in preventative maintenance of asphalt pavement. UTFC could be also used as the wearing course of newly constructed pavements. This study investigated the effects of reclaimed asphalt pavement (RAP) and glass fiber on the fracture behaviors of UTFC at the low and intermediate temperatures. At the low temperature (-10℃), fracture energy, stress intensity factor and cracking resistance index (CRI) were obtained to present the fracture behaviors of three types of UTFC mixtures. At the intermediate temperature (25℃), the size-independent fracture energy considering the tail part of the load–displacement curves were obtained. Besides, J-integral, cracking resistance index (CRI) and balanced cracking index (BCI) were obtained to characterize the intermediate fracture performance. Results indicated that at −10 ℃, the incorporation of RAP weakened the fracture resistance of UTFC; while the addition of glass fiber could counteract the adverse effect of RAP. Besides, CRI value of UTFC with glass fiber was the largest, indicating the superior fracture resistance at the low temperature. At 25 ℃, UTFC presented the best cracking resistance in terms of fracture energy, J-integral, CRI values and BCI values, indicating the incorporation of RAP could deteriorate the fracture resistance at the intermediate temperature. When both RAP and glass fiber were added in UTFC, the fracture performance was deteriorated furtherly, which may be possibly caused by the non-uniform distribution of fiber. On the other hand, the bonding strength between fiber and asphalt could be mitigated when temperature increased from −10 ℃ to 25 ℃. The size-independent fracture energy of UTFC was the largest, indicating the superior fracture resistance, followed by UTFC-50% RAP-F and UTFC. It was also reported that the incorporation of fiber improved the ability to tolerate deformation.