Influence of limestone fillers on combustion characteristics of asphalt mortar for pavements

Asphalt materials will be ignited and release significant toxic fumes within tunnel fires. Thus, combustion characteristics of asphalt materials used in road tunnel should be studied in order to limit such an adverse effect. In the present work we study the influence of limestone fillers on combustion characteristics of asphalt mortar by thermogravimetric and kinetic analysis. It is shown that the combustion of asphalt mortar is not just a linear superposition of asphalt and limestone. The limestone will increase the ignition point and the activation energy of the primary volatile release, and will catalyze the char formation from the primary volatile release. Kinetic analysis shows that the primary volatile release stage of asphalt mortar combustion can be explained by a three-dimensional diffusion model, the secondary volatile release and char combustion stage can be explained by a model under the assumption of random nucleation and nuclei growth, whereas the limestone decomposition stage appears to follow the one-dimensional phase boundary model.

Non-isothermal kinetics of styrene-butadiene-styrene asphalt combustion

The combustion characteristics of styrene-butadiene-styrene(SBS) asphalt are studied by thermogravimetric analysis(TG/DTG) at four different heating rates.According to the saturates/aromatics/resins/asphaltenes(SARA) fractionation method,the combustion process of SBS asphalt can be divided by Gaussian peak fitting into three main stages:oil content release,resin pyrolysis,and asphaltene and char combustion.When the heating rate increases,the mass losses of the oil content and resin pyrolysis increase,and less asphaltenes are formed at a higher temperature.The activation energy values are calculated by the Coats-Redfern method to be in the range 61.6 kJ/mol-142.9 kJ/mol.The Popescu method is used for the kinetic analysis,and the result shows that the three stages of asphalt combustion can be explained by the sphere phase boundary reaction model,the second order chemical reaction model,nucleation,and its subsequent growth model,respectively.