Effect of chemical modification on rheological properties of asphalt

At present, there have been many research results on the relationship between the microscopic and macroscopic properties of asphalt from the perspective of asphalt chemical composition and microstructure. However, asphalt is a colloidal material that exists in an aggregated form. In addition to its chemical composition and microstructure, its intermolecular forces will also greatly affect the performance of asphalt.In order to understand the connection between the rheological properties of asphalt and the forces between asphalt molecules, this study used two chemical modification methods, methylation, and carboxylation, to change the interaction strength between asphalt molecules and explore the impact of chemical modifications on the rheological properties of asphalt. Fourier transform infrared spectroscopy analysis showed that the modified asphalt had been successfully prepared, and frequency scanning was performed at different temperatures with the help of a dynamic shear rheometer to construct the master curve. The results showed that the elasticity of methylated asphalt was negatively related to the degree of methylation, and the opposite was true for viscosity; The elasticity of carboxylated asphalt initially increased and then decreased as the carboxylation degree increased, and the opposite was true for viscosity. In addition, the influence of chemical modification on the volume fraction of the dispersed phase in asphalt was investigated. It was observed that methylation of asphaltene weakened the hydrogen bonding, increased the distance between asphaltene molecules, and resulted in the reaggregation of asphaltene. Colloids with large particle sizes were removed, and the volume fraction of the dispersed phase decreased as the degree of methylation increased, resulting in a decrease in asphalt elasticity. After carboxylation modification, the hydrogen bonding between asphalts was enhanced. In the early stage, the colloidal particle size was reduced, the volume fraction of the dispersed phase was increased, and the elasticity of the asphalt was improved. When the carboxylation reached a certain level, the asphaltene molecules were further associated with each other, and the original content in the system was reduced. Some colloids also tended to aggregate with each other, the colloid particle size became larger, the volume fraction of the dispersed phase decreased, and the asphalt elasticity decreased.