Dynamic evolution of emitted volatiles from thermal decomposed bituminous materials

• The pyrolysis behavior of bituminous materials in nitrogen was investigated.
• The dynamic evolution of volatiles evolved from bitumen pyrolysis were characterized.
• The overall releasing evolutions of each main pyrolysis products were analyzed.
• The pyrolyzed regularity of flammable volatiles was discussed at flash and fire points.
• The microscopic pyrolysis mechanism of bitumen materials was further studied.

Bituminous material is widely utilized in building waterproof, pavement engineering, etc. However, when the fire happens, hazardous fumes are released due to bitumen decomposition, affecting adversely the environment and human health. The thermal decomposition behavior of bitumen is the first step of its conversion process, such as combustion, and carbonization. To better understand the bitumen conversion when exposed to fire, the decomposition characteristics of bitumen was investigated and the dynamic evolution of gaseous products was characterized in this study. The results from thermogravimetry (TG) indicate that the decomposition of bitumen shows a single-step decomposition mechanism. The spectrum profiles from Fourier transform infrared spectroscopy (FTIR) further characterizes the decomposition mechanism and the overall evolution of volatiles from bitumen at flash and fire points. The evolved volatiles include carbon dioxide (CO2), carbon monoxide (CO), methane (CH4), water (H2O), nitrogen dioxide (NO2), sulfur dioxide (SO2), hydrocarbon, methanol, formic acid, phenols, aromatic compounds, etc. The vapor pressure is a main factor to determine the concentration and hazards of gaseous products during bitumen decomposition. It was found that the evolution of each gaseous product was concentrated from 60 min to 110 min and each volatile was emitted from different chemical compositions of bitumen at various temperature ranges.