Rheology and volatile organic compounds characteristics of warm-mix flame retardant asphalt

Abstract

Warm-mix flame retardant asphalt (WF-A) is widely used in tunnel pavement owing to its positive construction and workability, as well as excellent flame retardant performance. When flame retardant (FR) improves the flame retardancy of asphalt binders and warm mix agent reduces the construction temperatures, the combined effects of the two additives on asphalt binders’ performances need to be studied. In this study, through orthogonal experimental design, limiting oxygen index (LOI) test and viscosity test, the optimum WF-A was selected. Afterward, the service performances of WF-A were comparative analyzed with warm mixing asphalt, SBS modified asphalt and flame retardant asphalt, including construction temperatures, high-temperature rheological property and aging resistance. Additionally, the characteristics of volatile organic compounds (VOC) emission are assessed by gas chromatography mass spectrometry (GC–MS). The results show that the optimum WF-A is that with the content ratio of 3.5% EC-120 and 8% FRMAX under the mixing temperature of 150 °C, and warm mix agent (EC-120) can obviously reduce the high-temperature viscosity of SBS modified asphalt binder, and increase the high-temperature fluidity; flame retardant (FRMAX) adversely affects the viscosity reducing effect of EC-120. The additions of the two additives are not conductive to the aging resistance of asphalt. Besides, both EC-120 and FRMAX have the effect of reducing asphalt fumes, and the optimum WF-A can reduce VOC emissions by 45.5% compared with SBS modified asphalt binder. The study provides significant references for further applying WF-A in the sustainable and safe construction of road networks.