NON-ISOTHERMAL DEGRADATION KINETICS OF ASPHALT IN RELATION TO ITS CHEMICAL COMPOSITION

摘要

Analysis of the complex and variable nature of the chemical composition of asphalt has been a challenge to engineers and scientists, especially as a means to understand its behavior and suggest ways to improve its properties. In this study, the elemental distributions based on the emission spectra of C, H, and O in asphalt samples were determined using Laser-Induced Breakdown Spectroscopy (LIBS), while the thermal behavior and the non-isothermal degradation kinetics were analyzed using the isoconversional methods, through Thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC). LIBS results show that the distribution of high and low C/H and 0/C wavelength intensity ratios vary between different Penetration Grades (PG) of asphalt despite the similarities in the percentage of the high and low ratio within the sample region. The results suggest that even if the asphalts may have similar elemental composition, the distribution of the components throughout the asphalt matrix affected the resulting physical properties of the material. TGA and DSC data show gradual change in the mass of the material at increasing temperature, suggesting behavior typical of a homogenous mixture. Kinetic analysis from the TGA data using the Starink modification of the Kissinger-Akahira-Sunose Isoconversional method show an apparent increase in the magnitude of the activation energies at different conversion degree, which suggests a gradual change in the composition of the material at each successive conversion due to a single heat-promoted transformation of each of the components.