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Volume 115
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Influence of RAP content on the mesostructure and mechanical response of recycled asphalt mixtures
Liwan Shi a, Zhiyong Hu b *, Hao Li c, Bohuang Lin d, Youwei Tan c, Yi Deng a
a School of Civil Engineering and Transportation, Foshan University, 528225, Foshan, China
b Wuhan Qingchuan University, 430204, Wuhan, China
c Foshan Transportation Technology Tiannuo (Guangdong) Materials Co., Ltd, 528000, Foshan, China
d National Engineering Laboratory of Highway Maintenance Technology, School of Traffic and Transportation Engineering, Changsha University of Science & Technology, 410114, Changsha, China
10.1016/j.partic.2026.05.019
Volume 115, August 2026, Pages 238-255
Received 13 February 2026, Revised 18 May 2026, Accepted 23 May 2026, Available online 4 June 2026, Version of Record 10 June 2026.
E-mail: 390496593@qq.com
Highlights

• DEM models with crushable coarse aggregates were developed to accurately distinguish new aggregates and RAP.

• Stress characteristics in different regions and among various meso-structure components were analyzed.

• The concept and characteristics of slip-band structures in recycled asphalt mixtures were defined.

• The evolution laws of slip-bands and aggregate breakage with different RAP contents were revealed.


Abstract

The road performance of recycled asphalt pavement (RAP) is crucial for low-carbon road construction. However, existing studies lack refined simulation of the mesostructure involving RAP, new aggregates, aged asphalt, and new asphalt, leaving the effects of different RAP contents on stress distribution and damage mechanisms unclear. This study develops discrete element models to analyze the influence of RAP content on mesoscopic stress evolution, crack propagation, and aggregate breakage. The results show that when RAP content exceeds 45%, aged asphalt and RAP exhibit notably non-uniform distributions. The maximum normal stress occurs at the loading center, while the maximum shear stress is located at the bottom sides of the loading center. As RAP content rises from 15 % to 60 %, the number of effective microcracks increases by 2.04 times. The length and area of slip-bands grows rapidly, and the crack damage index D follows an exponential upward trend. Considering rutting resistance, crack resistance, and resource utilization efficiency comprehensively, the recommended suitable RAP content range is 30 % – 45 %, with the following threshold values: number of slip-bands≤8, average length of slip-bands≤48 mm, and D ≤ 7.5 %. The findings provide a theoretical basis for understanding the meso-mechanical behavior of recycled asphalt mixtures.

Graphical abstract
Keywords
Recycled asphalt mixture; Discrete element method; Stress distribution; Microcrack; Aggregate breakage
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