The composition of asphalt is complex and flammable. When burning, it emits a lot of heat, smoke and toxic gases. Once a fire accident is caused, improper handling will cause incalculable losses. Therefore, it is an important topic to improve the flame retardant performance of asphalt pavement. Flame retardant asphalt is the addition of flame retardants to asphalt, which can be used alone or in combination with a variety of flame retardants to form a synergistic flame retardant system.
 

Asphalt flame retardant is also called asphalt flame retardant smoke suppression agent, must meet the five major properties:

First, high flame retardant efficiency, low smoke, low toxicity, safety and environmental protection, so that it is economical;

Second, the thermal stability is good, and the decomposition temperature of the flame retardant is 250-400 ℃, which can prevent combustion to the maximum extent;

Third, the compatibility is good, which has little influence on the performance of asphalt and asphalt mixture, and improves the performance of pavement.

Fourth, the water solubility is small, the durability is good, and the flame retardant performance is durable; the insoluble water can make the flame retardant play a more lasting role.

Fifth, the price is low, the source is wide, and the manufacturing is simple.

The flame retardant that meets these five conditions is called 5A asphalt flame retardant.

The combustion process of asphalt mainly includes heat absorption, coverage, inhibition of chain reaction and asphyxiation of non-combustible gas. When asphalt burns, it releases various flammable gases. These gases further aggravate the thermal decomposition of asphalt, forming a vicious circle. So asphalt flame retardant smoke suppression agent must have the following four functions:

First, asphalt flame retardant can absorb the heat released by asphalt combustion, reduce the surface temperature of combustible materials, effectively inhibit the generation of combustible gas, and avoid secondary combustion;

Second, the asphalt flame retardant can form a stable carbonized layer on the asphalt surface, heat insulation, oxygen insulation, prevent combustible gas from escaping outward, so that the combustion is terminated, resulting in self-extinguishing, equivalent to an isolation cover;

Third, asphalt flame retardant can capture the active free radicals (HO-and H-) in the early stage of combustion, inhibit the occurrence of chain reaction, and fundamentally prevent combustion;

Fourth, asphalt flame retardant can break down the non-combustible gas, dilute the oxygen concentration and combustible gas concentration in the combustion zone, and prevent the spread of combustion.

The asphalt flame retardant generates strong dehydrating agent when heated at high temperature, which dehydrates and carbonizes the asphalt surface, isolates the external combustible gas and heat, and inhibits 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, economic application, is an ideal flame retardant.