Key points are not available for this paper at this time.
The goal of this research is to evaluate the changes in fatigue and age-related cracking properties of asphalt mixes due to the addition of high contents (up to 50 % binder replacement) of reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS), and recycling agents (RA). To achieve this goal, a total of 18 binder blends along with their corresponding selective mixes have been fabricated and tested in the laboratory. The collection of mixes includes one gradation with 0.5-inch nominal maximum aggregate size (NMAS), two virgin binders (PG 64–16 and PG 58–28), two RAPs with different levels of aging (PG high of 102°C and 109°C, respectively), one RAS, and two recycling agents (aromatic-based and tall oil-based). The testing of the binder blends includes PG-grading and frequency-sweep dynamic modulus tests. The testing of the mixes includes stiffness, four-point bending (4PB) fatigue resistance, and IDEAL cracking test. The main conclusion from this study is that most of the negative effects on both kinds of cracking of RAP/RAS addition can be mitigated by using RA and/or step-down binders. The results of this study indicate that mix stiffness and indirect tensile strength (ITS) showed strong correlations with different parameters obtained from fabricated binder blends. On the contrary, the blended binder and mix properties which primarily focus on stiffness, and do not involve repeated loading, did not correlate well with the 4PB fatigue life. The main difference between the two RAs was that the aromatic required a higher dose (around 60 % higher) than the tall oil to produce similar effects on the mechanical properties of asphalt mixes. • The negative effects of RAP/RAS addition on cracking performance can be mitigated using RA and/or step-down binders. • None of the binder or mix properties correlate well with the asphalt mix fatigue performance. • A lower dose of tall-oil-based RA is needed to achieve a similar effect.
Rahman et al. (Sat,) studied this question.