Inhibitory action of flame retardant on the dynamic evolution of asphalt pyrolysis volatiles

It is important to inhibit the pyrolysis behavior of asphalt binder for improving its flame retardancy. The inhibitory effects of magnesium hydroxide (MH) on the asphalt pyrolysis were investigated in this study. The results indicated the thermal stability of asphalt materials was improved by MH. The starting time of asphalt pyrolysis was delayed by MH in a timely manner, and the releasing amount of gaseous products was also reduced. The qualitative composition of main volatiles evolved from asphalt/MH composite is similar to that of pure asphalt binder, including carbon dioxide, methane, water, carbon monoxide, sulfur dioxide, aromatics, hydrocarbons, etc. Each main volatile was emitted from different chemical compositions of asphalt binder at various temperature ranges. It was found that the reaction between asphalt binder and MH was only a physical blending process. The fire safety of asphalt materials was elevated by MH, but no additional secondary hazards were generated. The flame-retarding purpose of asphalt materials was achieved because of the effects of cooling, blocking and diluting in the condensed and gas phase due to MH decomposition. It is believed that MH can be utilized as a new environment-friendly flame retardant for asphalt binder at a lower loading.