Effects of flame-retardant nanocomposite combined with warm mix asphalt techniques on molecular conversion and fire safety

The combination of flame retardant with warm mix asphalt (WMA) technology in asphalt pavements has become an important strategy for improving safety, conserving energy, and safeguarding the environment, especially in tunnel applications. This study explored the incorporation of flame-retardant nanocomposite and three distinct types of WMA additives into asphalt to investigate the mechanisms underlying the modification process and fire safety. Additionally, warm-mix asphalt samples without flame retardant were analyzed as control specimens for comparative analysis. The WMA additives notably enhanced the dispersion of flame-retardant nanocomposite and facilitated the conversion of medium and large molecules within the asphalt matrix. The combination of the organic WMA additive and flame-retardant nanocomposite provided superior flame retardancy and smoke suppression properties compared to asphalt that contained only flame retardant. The peak heat release rate and peak smoke production rate were significantly reduced by 45.5 % and 45.7 %, respectively. The detailed analysis indicated that the flame-retardant mechanism primarily resulted from the char layers reinforced by the continuous crystal grid structures in the asphalt, alongside the inert gases released by the flame-retardant nanocomposite. These results underscore the potential and significance of flame-retardant warm-mix asphalt for engineering applications.