Review of the flame retardancy on highway tunnel asphalt pavement

Though asphalt pavement is widely used in highway tunnels, the flammability of the asphalt pavement is still one significant topic for an in-depth study due to the serious consequences of the tunnel fire. This paper presents a review of the flame retardancy on highway tunnel asphalt pavement. Firstly, the combustion of asphalt pavement and cement pavement is compared on the basis of highway tunnel fire, the commonly used asphalt flame-retardant evaluation standards are analyzed. Secondly, flame-retardant technologies including flame retardant, component flame-retardant method and porous structure flame-retardant method are summarized. Furthermore, the application of nanotechnology in flame-retardant asphalt is reviewed. Finally, concluding remarks and important future investigation directions are presented, which will be advantageous to future study the flame retardancy on highway tunnel asphalt pavement. (C) 2018 Elsevier Ltd. All rights reserved.