Interactions between RAP and virgin asphalt binders in field, plant, and lab mixes

Reclaimed asphalt pavement (RAP) has been used in asphalt mixes for several years in the United States. However, the interactions between the RAP binder and the virgin asphalt binder (VAB) need further investigations. Thus, the main objective of this study was to explore the rheological and chemical properties of extracted asphalt binders (EABs) from plant, field, and lab mixes. The plant mixes were collected from behind the paver, reheated to the compaction temperature, and compacted in the lab. The field mixes were collected as cores within two weeks after the end of the construction process. The lab mixes were fabricated in the lab using the same materials used in the plant and field mixes. The mixes contained high asphalt binder replacement percentages by RAP, which were greater than 30%. The EABs were treated as rolling thin film oven aged VABs (RTFO AVABs). The rheological properties of EABs and RTFO AVABs were analyzed using temperature sweep, frequency sweep, and multiple stress creep recovery tests. Chemical investigations of EABs and RTFO AVABs were carried out using Fourier transform infrared spectroscopy and thermogravimetric analysis. The EABs from plant or lab mixes showed higher stiffnesses than EABs from field mixes. This occurred because of the extra heating that was implemented for the plant mixes before the compaction in the lab, which caused more interactions between the RAP binder and VABs. The fabrication mechanism, mixing and short-term aging processes, used in lab mixes caused more interactions between RAP binder and VABs than in the field mixes.

Characterization of asphalt binders extracted from field mixtures containing RAP and/or RAS

The use of reclaimed asphalt pavement (RAP) and/or recycled asphalt shingles (RAS) in the asphalt mixtures is a common practice in the U.S.A. However, there is a controversy to date on how RAP/RAS interact with virgin asphalt binders (VABs) in asphalt mixtures. For mixtures containing RAP/RAS, the aged asphalt binders in RAP and air-blown asphalt binders in RAS alter the performances of the extracted asphalt binders (EABs). Thus, the rheological properties of EABs from these mixtures require more investigation. The focus of this paper was relating the high-temperature properties of EABs from field cores to the corresponding rolling thin film oven aged virgin asphalt binders (RTFO AVABs). Furthermore, a comparison of the effect of RAP and RAS on the high-temperature rheological properties of EABs was another objective. Different asphalt cores were collected from the field within two weeks after the pavement construction process in 2016. These cores represented eight asphalt mixtures with different asphalt binder replacement percentages by RAP, RAS, or both. The asphalt binders were extracted from these mixtures and considered as RTFO AVABs. The high-temperature rheological properties included the temperature sweep and frequency sweep testing and the multiple stress creep recovery testing. The EABs had higher stiffnesses and elasticates than the corresponding RTFO AVABs because of the aged binders in RAP/RAS. The binders in RAP interacted more readily with VABs than RAS binders.

Recycled Polyethylene Modified Asphalt Binders and Mixtures: Performance Characteristics and Environmental Impact

This study addresses the effects of recycled polyethylene (RPE) on the performances of both asphalt binders and asphalt mixtures. Whether using RPE in an asphalt mixture might leach harmful chemicals into rainwater or melted snow was also determined. Two processes, wet and dry, were used to formulate the RPE modified asphalt binders and mixtures. In the wet process, RPE was added to asphalt binder. In the dry process, it was added to heated aggregates. RPE from two sources and PG 64-22 virgin asphalt binders from two sources were used in this study. In conclusion, RPE improved the rutting resistance of the asphalt binders and asphalt mixtures. However, it had adverse effects on their resistance to intermediate-temperature and non-load associated cracking. The dry process could produce a mixture with a higher RPE dosage compared with the wet process using one virgin asphalt binder but not the other; thus, the virgin asphalt binder source was a significant factor for the dry process. Based on an embryotoxicity test, it was found that RPE can be used by the asphalt paving industry without creating any significant environmental risks.

Study Investigating the Influence of Warm-Mix Asphalt Additives on Rutting and Fatigue Performance of Nano-Modified Asphalt Binders

The current study investigates the synergized effect of a nanomaterial and two warm mix additives asphalt (WMA) additives on different properties of asphalt binders. The study used an optimal percentage of 2% for nano-Al2O3; two WMA additives were used in different concentrations. The results revealed that the addition of WMA additives increased the softening point of nano-Al2O3 modified asphalt binder. Penetration and ductility results showed a decrease after the introduction of WMA additives. The viscosity of nano-Al2O3 modified asphalt binders showed a reduction after the introduction of WMA additives. Rutting evaluation was done by using the superpave rutting parameter and multiple stress creep and recovery (MSCR) test. The fatigue performance of the asphalt binders was measured using the superpave fatigue parameter and linear amplitude sweep (LAS) test. Results showed that the introduction of WMA additives improved the rutting and fatigue performance of nano-Al2O3 modified asphalt binders. The introduction of WMA additives enhanced the aging performance of the nano-Al2O3 modified asphalt binders.