How Does High RAP Content Affect the Performance Properties and Durability of Rubberized Asphalt Mixtures?

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How Does High RAP Content Affect the Performance Properties and Durability of Rubberized Asphalt Mixtures?

Mohammad Zia Alavi¹*, Mohsen Amjadi¹, Mohammad Akhaghi¹

¹School of Civil Engineering, College of Engineering, University of Tehran, Tehran, Iran.

Zia.alavi@ut.ac.ir (corresponding author)

ABSTRACT. This study investigates the performance of rubberized asphalt mixtures incorporating 30%, 50%, and 70% Reclaimed Asphalt Pavement (RAP) by total mix weight. The binder was produced via the wet process using PG58-22 and 20% fine crumb rubber. To counteract potential performance loss at higher RAP levels, a rejuvenating additive was introduced in the 50% and 70% mixtures.

Performance was evaluated through four tests: Indirect Tensile Strength (ITS) under dry and wet conditions, Semi-Circular Bend (SCB) fracture test at 25°C, Beam Fatigue test at 20°C, and Dynamic Creep test at 54°C. RAP incorporation showed notable benefits in moisture resistance, as ITS and Tensile Strength Ratio (TSR) values increased with RAP content. Dynamic creep tests revealed substantial improvements in rutting resistance; RAP mixtures achieved Flow Number values 7.5 to 9.6 times greater than the control. SCB testing showed enhancement in peak load and fracture toughness across all RAP levels. However, fracture energy declined with higher RAP content: +8%, –7%, and –13% for 30%, 50%, and 70% RAP, respectively, indicating reduced flexibility. Even with rejuvenation, Flexibility Index values dropped. In fatigue testing, specimens endured 180,000 cycles at 600 µε without failure. At 800 µε, fatigue life decreased relative to the control, yet high RAP mixtures demonstrated improved fatigue behavior, likely attributed to rejuvenator efficiency.

Overall, RAP-enriched rubberized asphalt mixtures exhibited improved durability over conventional mixes. While high RAP content may compromise flexibility and fatigue life, the application of rejuvenating additives can effectively restore performance. Dense gradation across all mixtures further supports their suitability for sustainable pavement applications.

KEYWORDS: reclaimed asphalt pavement (RAP), rubberized asphalt mixtures, performance properties, rejuvenation, sustainable pavement.