Flame retardancy of asphalt mixtures and mortars containing composite flame-retardant materials

To investigate the flame retardancy of asphalt mixtures containing composite flame-retardant materials (M-FRs), four different asphalt mixtures were prepared: a reference asphalt mixture with common cellulous fibre and three mixtures with M-FRs of different compositions. The degradation of mechanical property and burning loss of asphalt binder during the burning process were introduced to evaluate the flame retardancy of asphalt mixtures. The results show that the residual dynamic stabilities of the asphalt mixtures containing M-FRs are 83.2%, 75.1% and 77.8%, respectively, which are greater than that of the asphalt mixture with cellulous fibre. After burning and freeze-thaw test, the split strength ratios of asphalt mixtures containing M-FRs show less attenuation than the common asphalt mixture, and the values are 80.2%, 72.3%, 84.4% and 69.4%. Moreover, the burning loss rates of asphalt binders are 22.0%, 8.2%, 8.5% and 12.8%, respectively. Besides, Limit Oxygen Index test, thermogravimetry and difference scanning calorimetry were used to analyse the flame retardancy and pyrolysis behaviour of M-FRs asphalt mortar. All the tests above prove that asphalt mixtures and mortars containing M-FRs have good flame retardancy.