Mechanical Properties of High-Modulus Asphalt Concrete Containing Recycled Asphalt Pavement: A Parametric Study

The recycling of asphalt pavement is a widespread practice around the world owing to its significant social, economic, and environmental advantages. High-modulus asphalt concrete (HMAC) possesses excellent rutting resistance and has received increased attention around the world. While many studies have been conducted on the performance of hot mix asphalt (HMA) containing reclaimed asphalt pavement (RAP), gaps remain in knowledge about producing HMAC containing RAP. This paper aims to investigate the performance of HMAC containing high percentages of RAP by conducting parametric laboratory tests. Design factors, including aggregate gradation, asphalt binder content, recycling agent dosage, and asphalt binder type, are evaluated in the laboratory. Tests conducted include dynamic modulus test, Marshall immersion test, modified Lottman test, three-point bending test, and rutting test. A modified regeneration method with adjusted mixing sequence is adopted to produce a mixture. It was found that low-penetration virgin-grade asphalt binder could produce good-quality HMA, though low-temperature cracking resistance remains a problem. Adjusting aggregate gradation and increasing asphalt binder content could improve its overall performance but not low-temperature cracking resistance. Increasing the dosage of aromatic extract recycling agent could improve HMA's low-temperature cracking resistance, and a maximum dosage of 6% was proposed. Increasing the penetration grade of virgin asphalt binder with the addition of high-modulus additive could significantly improve its low-temperature and overall performance.