Thermal behaviors and harmful volatile constituents released from asphalt components at high temperature.

Asphalt binder releases lots of heat and harmful volatiles at high temperature. To further understand thermal behaviors, dynamic release and toxic constituents of emitted volatiles during the combustion of asphalt binder, such fractions as saturates, aromatics, resins and asphaltenes (SARA) were first prepared. Thermal behaviors, volatile constituents and combustion residue microstructures of SARA fractions are discussed. Results indicate that polymerization degree of asphalt binder is high and the content of polycyclic aromatic compounds is large. Combustion processes of resins and asphaltenes only show single-stage exothermic reactions, but other two fractions present obvious multi-stage combustion reactions. As the heating rate is raised, the incomplete combustion of SARA fractions is increased, and more volatiles are released. Main volatiles released from SARA fractions are inflammable, toxic, corrosive or explosive compounds, and such common volatiles as acetaldehyde and propane are released from each SARA fraction. More toxic volatiles are released at combustion stage I, but macromolecular volatiles are mainly released at stage II. Volatile release behaviors of saturates and aromatics are more obviously affected by the heating rate. Combustion residues show more intact morphologies from saturates to asphaltenes, and mainly contain C, O and S elements. Asphalt binder is hazardous material at high temperature.