Effect mechanism of old asphalt on microstructure and mechanical properties of hot reclaimed pavement materials

ABSTRACT

Asphalt mixture recycled technology (Al-Saffar et al. 2021) is an efficient method for achieving asphalt pavement sustainability. The optimum asphalt content of recycled asphalt mixture is first determined by the Marshall test in this paper. Second, Materials Studio software was used to simulate the interface effect between three different asphalts and aggregate, and the adhesion between asphalt and aggregate was characterised based on the interface energy. The mesoscopic structural characteristics of three asphalt mixtures were then analysed using digital image processing technology. Finally, through three macro experiments, the influence of old asphalt on the mechanical properties of recycled asphalt mixture was studied from a macro perspective. At the microscopic level, the results show that the presence of the old asphalt reduces the adhesion between the asphalt and the aggregate. At the mesoscopic level, the presence of old asphalt reduces the porosity of the asphalt mixture. At the macroscopic level, the addition of old asphalt improves the high temperature and water stability of recycled asphalt mixture while decreasing the low temperature crack resistance. The microscopic and mechanical properties of old asphalt on recycled asphalt mixture are explained on three levels, and new ideas for research on recycled asphalt mixtures are provided.

KEYWORDS:

• Asphalt recycled pavement
• micro-structure
• molecular dynamics
• image processing technology
• void ratio

Research limitations and further work

1. In this paper, the recycled asphalt mixture contains only 40% PAR. We hope to find a suitable external admixture to increase the RAP content in future work.

2. The proportion of each component of miscible asphalt is not accurate enough in molecular simulation. It is hoped that future research will allow the proportion of each component of miscible asphalt to be calculated more precisely, so that it is closer to the true state.

3. The scanning section’s accuracy may be insufficient for microscopic analysis. Following research is expected to use industrial CT or nuclear magnetic resonance to obtain a more accurate specimen section.

Acknowledgments

The authors gratefully appreciate the supports from the province key laboratory of road in Northeast Forestry University and the foundations for the project of National Natural Science Foundation of China (E080703) and the project of Heilongjiang Traffic and Transportation Department.

Disclosure statement

No potential conflict of interest was reported by the author(s).