According to the combustion process of asphalt, the flame retardant principles of asphalt flame retardant mainly include heat absorption, coverage, inhibition of chain reaction and non-combustible gas asphyxiation. The combustion of asphalt is a physical and chemical process of heat release and decomposition, which decomposes hydrogen, methane, stupid and alkane flammable gases. The combustion of these gases further accelerates the thermal decomposition of the pitch. According to the combustion process of asphalt, in the event of a fire on asphalt pavement, in order to achieve the purpose of flame retardant suppression, the added flame retardant and smoke suppression agent should have the following functions: 1. It can absorb the heat released by combustion, reduce the temperature of the surface of combustible materials, and effectively inhibit the generation of combustible gases. 2, can form a stable carbonization layer on the surface of asphalt, heat insulation, oxygen insulation, prevent combustible gas from escaping outward, so that the combustion is terminated, resulting in self-extinguishing. 3. It can capture the highly active free radicals (HO-and H-) in the early stage of combustion and inhibit the occurrence of chain reactions. 4, can be separated from the non-combustible gas, dilute the combustion zone oxygen concentration and combustible gas concentration, to prevent the spread of combustion.

Halogen flame retardants are mainly bromine flame retardants, which have good flame retardant effect, but a large amount of toxic smoke will be released during the flame retardant process, and decabromodiphenylether will also produce carcinogens during the combustion process. And the cost is high.

Nitrogen phosphorus flame retardant, when heated at high temperature to generate strong dehydrating agent, so that the asphalt surface dehydration carbonization, isolated from the outside of the combustible gas and heat, inhibit the combustion. At the same time, it decomposes to generate ammonia and water vapor when heated, and the oxygen concentration in the air is diluted by ammonia, which has a good flame retardant effect. In addition, good thermal stability, poor water solubility, low smoke, low toxicity, economical and practical, is an ideal flame retardant.

Non-halogen composite flame retardant, in the combustion, release the combined water, absorb a large amount of heat, thereby inhibiting the combustion, combined water at high temperature and carbon particles further oxidation reaction, reducing the generation of flue gas, so as to achieve the dual purpose of flame retardant smoke suppression. Considering the problems of ring, low carbon energy saving and cost, the halogen-based flame retardants are mainly replaced by nitrogen-phosphorus-based and composite non-halogen flame retardants.