Characterizing bitumen-aggregate interfacial failures under coupled size effects of bitumen film thickness and aggregate surface roughness

• Published in: Construction & building materials Vol. 416; p. 135238
• Main Authors: Wang, Juntao, Cao, Shunqin, Luo, Xue, Zhang, Yuqing
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 16.02.2024
• Subjects: Aggregate surface roughness; Bitumen film thickness; Bitumen-aggregate interface failure; Modified Kendall model; Pull-off test; Aggregate surface roughness; Modified Kendall model; Pull-off test; Bitumen-aggregate interface failure; Bitumen film thickness
• ISSN: 0950-0618; 1879-0526
• DOI: 10.1016/j.conbuildmat.2024.135238

Bitumen-aggregate interfaces are the weak points in asphalt mixtures determining the material failure. Previous studies were focused on interfacial failure without a clear understanding to the coupled size effects of bitumen film thickness and aggregate roughness on the failure mechanisms. This study investigates the bitumen-aggregate interface failure mechanisms with the coupled size effects and provide a mechanistic model for interface pull-off strength prediction. Pull-off tests were conducted at five levels of aggregate roughness (0.803 µm-22.09 µm) and four bitumen film thicknesses (30 µm-60 µm). A modified Kendall model was developed to predict the interface pull-off strength, addressing the coupled size effects. Results indicate that a thin bitumen film thickness (30 µm-40 µm) and a low surface roughness (<2.36 µm) yield a higher pull-off strength(1225–1470 N). Thicker bitumen films showed more cohesive debonding, reducing the pull-off strength. When aggregate roughness increases but remains below 2.36 µm, the contact area increases, resulting from an interlocking effect between bitumen and aggregate. Beyond 2.36 µm, aggregate surface spines appear and puncture bitumen film, causing a decreased contact area and decreased pull-off strength. The modified Kendall model can accurately (within a 10 % error) predict bitumen-aggregate interfacial pull-off strength accounting for the coupled size effects of the bitumen film thickness and aggregate surface roughness. [Display omitted] •Thinner bitumen film causes higher interfacial bonding before being punctured.•Lower roughness (<2.36 µm) reduced interfacial bonding by less contact areas.•Higher roughness (>5.01 µm) reduced interfacial bonding by punctured bitumen films.•Interfacial pull-off strength is modeled by a mechanistic model with size effects.