Recycling highway construction materials and minimising the use of virgin materials can reduce the pavement life cycle costs, improve highway network condition, conserve natural resources, and ...protect the environment. However, aged binder in reclaimed asphalt pavement (RAP) and recycled asphalt shingle (RAS) makes asphalt pavements more brittle and creates long-term durability problems. In this study, the performance benefits of using softer virgin binder grade and increased virgin binder content strategies in RAP and RAS mixture production in Oregon were quantified. Semi-circular bend and flow number tests were conducted on prepared samples in laboratory to assess their cracking and rutting performance with low or no RAP (0% and 15%), high RAP (30% and 40%), and RAP&RAS, three binder contents (total binder contents with RAP/RAS and virgin binder - 6%, 6.4%, and 6.8%), and three binder grades (PG 58-34, PG 64-22, and PG 76-22). Moreover, possible combinations of RAP/RAS content, binder content, and binder grade to produce asphalt mixtures with high cracking and rutting performances were suggested using regression modelling and sensitivity analysis. The results of this study show that increasing binder content does not create any significant impact on the cracking performance of RAP&RAS mixtures but it is an effective strategy to improve the fatigue cracking resistance of 30% and 40% RAP mixtures.
•SCB and IDT tests are the most reliable tests to evaluate fatigue cracking.•Flexibility index parameter is effective in differentiating cracking resistance.•Mixing method does not have significant ...effect on measured cracking performance.•Compaction method significantly affects the measured cracking resistance.
Cracking is a common failure mechanism in asphalt concrete pavement structures. It is one of the main reasons for large road maintenance and rehabilitation expenditures, as well as reduced user comfort and increased fuel consumption due to high road roughness. The resistance of the pavement to this distress mechanism is dependent upon the ductility of the asphalt pavement mixture. The use of recycled asphalt materials in asphalt mixtures are also becoming increasingly common. A drawback of this practice is a reduction in ductility of the asphalt mixture, which causes a significant reduction in the fatigue life of the pavement in many cases. In Oregon, asphalt pavements are commonly failing prematurely due to cracking-related distresses, necessitating costly rehabilitation and maintenance at intervals of less than half of the intended design lives in some cases. For this reason, it is necessary to accurately quantify the impact of increasing the recycled asphalt content in asphalt pavement on the structural cracking resistance of the pavement through the use of low-cost and efficient testing procedures that can be implemented easily. This study focuses on characterizing the cracking performance of asphalt pavements in Oregon by considering four tests commonly used to evaluate fatigue cracking resistance and proposing the implementation of the most cost-effective and efficient test procedure for agencies and contractors.
