Flame Retardancy and Rheological Properties of Warm-Mix Rubber Asphalt Binder Containing Various Flame Retardants

Abstract

The application of warm-mix flame retardant rubber asphalt (WFRA) in tunnel pavement offers a promising solution that enhances both energy conservation and tunnel safety. First, a commercial halogen-free flame retardant (ZK), alumina trihydrate (ATH), and organic montmorillonite compound ATH flame retardant (OMMT/ATH) were melt-blended with warm-mix rubber asphalt (WRA) to prepare different types of WFRAs. Then, the effects of various flame retardants (FRs) on flame retardancy and rheological properties of the WRA were evaluated. Moreover, the functional groups of FR, WRA, and WFRA were investigated. Finally, the synergistic mechanism of FR on the WRA was explored based on the analysis of flame retardancy, rheological properties, and functional groups. Results show that the flame-retardant effect of OMMT/ATH on the WRA is much better than that of single FRs (ZK and ATH), indicating that the OMMT and ATH exhibit synergistic flame-retardant effect. The addition of OMMT/ATH enhances the high-temperature performance but shows little effect on the fatigue performance of the WRA. The synergistic flame-retardant mechanism of OMMT/ATH on the WRA is mainly attributed to the physical barrier effect of OMMT, the cooling and dilution effect of ATH, and the synergistic covering layer effect of OMMT and ATH.