Effect of reclaimed asphalt pavement (RAP) on fracture properties of stone matrix asphalt (SMA) at low temperature

Abstract

In this research, the fracture properties and low temperature cracking of stone matrix asphalt)SMA(mixture containing reclaimed asphalt pavement)RAP(were evaluated. To achieve appropriate gradation of SMA with a nominal maximum aggregate size (NMAS) of 12.5 mm, 30 % dense graded RAP was used. Evaluation of fracture properties was done based on stress and energy approaches. To evaluate the fracture properties of the SMA mixture containing 30 % RAP and compare it with the non-RAP mixture, semicircular bending (SCB) test was performed at −10 °C. Air void in the mixture (Va), loading rate, and combined mode parameter (Me) was considered as research factors. The results showed that the critical stress intensity factor (KIC) of mixtures containing 30 % RAP was higher than the non-RAP mixture. In both types of mixtures, with increasing Me, KIC first decreased and then increased. In pure mode I (Me = 1) with increasing air void, KIC decreased. Regardless of the effect of RAP, in all fracture loading modes with increasing loading rate and air void, the fracture energy (Gf) decreased. Therefore, the presence of RAP did not affect the energy absorption of the mixture at low temperatures. The presence of RAP and coarse aggregate skeleton structure causes the brittle fracture of the mixture at low temperatures. The effect of RAP on the crack path only in samples with low air voids and high loading rate caused the crack path through coarse aggregates with smaller size and mastic to show a more share compared to non-RAP samples.