Preparation, properties, and mechanism of warm mix flame retardant modified asphalt based on surface activity principle

The compatibility of Nano-composite flame retardants (NCFR) with asphalt and high construction temperature of flame retardant modified asphalt are the main problems for application of flame retardant modified asphalt. Firstly, the surface of NCFR was pretreated by surface organic coating method to obtain surfactant-based warm-mix flame-retardants (SWF). Then the effect of SWF on the rheological properties and functional properties of asphalt was investigated. Finally, the performance improvement mechanism was revealed. The results show that the surfactants improved the compatibility of SWF with asphalt. Compared to NCFR-modified asphalt (NCFRMA), the high-temperature deformation resistance of SWF modified asphalt (SWFA) was reduced. Conversely, the deformation ability of SWFA at low-temperature was enhanced. SWF effectively reduced the combustion rate of asphalt, where the heat release rate (HRR) decreased by 21.98% and the smoke produce rate (SPR) decreased by 42.03%. The residual stability of the SWFA mixture after combustion were all higher than that of the NCFRMA mixture, but the loss on stability of SWFA mixture after combustion was greater. The surfactants improved the dispersion of NCFR with asphalt, which resulted in higher flame resistance. The optimum forming temperature of the SWFA mixture was reduced by 25 °C due to accelerated wetting between asphalt and aggregate.