Advancements of carbon nanomaterials-modified asphalt: Processes, properties, economic feasibility and future perspectives

Hot mix asphalt is the cornerstone of road design serving the basis of road networks in the transportation infrastructure of a country. Traditional formulations of hot mix asphalt suffer from inherent limitations such as susceptibility to rutting and cracking due to severity of temperature changes. Carbon nanomaterials (CNMs) feature superb properties such as mechanical strength, and thermal and electrical conductivity. Recently, adding CNMs into hot mix asphalt, as an alternative to conventional additives, proved to be effective in enhancing overall performance of asphalt concrete; for example, it enhances its Marshall stability, rutting resistance and low-temperature crack resistance leading to roads with high longevity and sustainability. In addition, CNMs can offer new functional properties into asphalt mixtures such as self-healing, and thermal and electrical conductivity. This review presents the recent advances in integrating CNMs, specifically graphene and carbon nanotubes (CNTs), into asphalt mixtures. Features of nanomaterials such as specific surface area, geometry, and their effect on the properties of hot mix asphalt are comprehensively discussed. The review also explores the processing and characterization methods for CNMs-modified asphalt binder and their impact on the mixture workability and rheological performance. Furthermore, the article elaborates the structure-property relations of CNMs-modified asphalt mixtures at the macroscale (mechanical properties), microscale (morphology and microstructure) and atomic scale (molecular dynamic simulations). Functional properties of CNMs-modified asphalt were also discussed. More importantly, the authors provided a roadmap and mathematical model to assess the economic feasibility and sustainability of incorporating CNMs into the asphalt industry. At the end, potential and research directions in adding CNMs into asphalt industry are outlined.