Geometric composition, structural behavior and material design for asphalt trackbed: A review

[Display omitted] •Four asphalt trackbeds are categorized from geometric features.•The structural performance requirements are summarized.•Asphalt-based material design and construction are characterized. Asphalt trackbed, as an asphalt-based design below rails, has been increasingly applied with numerous merits in railway substructure. In this paper, a state-of-the-art review is conducted to comprehensively summarize the research and application progress of railway asphalt trackbed, in terms of the typical geometric composition, structural mechanical behavior, and material design. This review indicated that (i) asphalt underlayment (AUL), asphalt overlayment (AOL), surface asphalt mixture impermeable (SAMI) and asphalt stabilized ballast (ASB), as geometry-based classifications are proposed; (ii) load distribution, bearing capacity, vibration control, and moisture resistance, as well as thermal viscoelasticity, are the common mechanical behaviors of AUL and AOL, while the latter more focuses on vibration control, noise reduction, and interlayer contact. For SAMI and ASB, the environmental effects and the bonding strength are more emphasized, respectively; (iii) the material design and construction are normally the same with those of highway asphalt pavement, except for lower air voids but solid wastes as aggregate and lower construction temperature more encouraged. However, the composition of asphalt mixture with high cost-effect and the fatigue behavior considering viscoelastic properties, as well as the rapid construction and maintenance methods on-site need further research.