Rejuvenation effect of aged SBS-modified asphalt utilizing molecule analysis

Abstract

The performance of styrene-butadiene-styrene modified asphalt (SBSMA) is significantly impacted by its aging and regeneration. In this research, the molecular dynamics simulation was utilized to investigate the rejuvenation effect of active reagents on aged SBS modified asphalt through the following tasks: 1) verifying the accuracy of the asphalt model by density and solubility parameters; 2) assessing the changes in the rejuvenated asphalt model's energetic parameters and volume parameters, 3) studying the interaction energy between SBS molecules and asphalt molecule models, and 4) evaluating the relative concentration, interfacial interaction energy, and diffusion effect of the asphalt-asphalt models. The results indicated that the restored broken SBS molecule substantially impacted the functionality of the rejuvenated asphalt binder. For Methylene-bis(4-cyclohexylisocyanate) (HMDI) and 1,6-Hexanediol Diglycidyl Ether (HDE) rejuvenated asphalts, the non-bond energy decreased gradually with the repair of broken SBS molecular structures. The free volume fraction of rejuvenated binders was lower than that of SBSMA, indicating that the compactness and packing degree of the rejuvenated asphalt were increased. The interaction energy between SBS and asphalt molecules in rejuvenated asphalt increased because of the enhanced van der Waals interaction between the reconstructed SBS molecule and rejuvenated binders. The free HDE molecular chain reduced the interaction energy between SBS and asphalt molecules. For the asphalt-asphalt models, the diffusion coefficient of the SBSMA-rejuvenated asphalt model was lower than that of the SBSMA-SBSMA model. The HDE rejuvenated asphalt showed better diffusion behavior than SBSMA, and SBS molecules repaired by HDE had excellent fluidity. The interfacial interaction energy of the SBSMA-rejuvenated asphalt model was higher than that of the SBSMA-SBSMA model. With the repair of the broken SBS molecular chain, the interfacial interaction energy between HMDI rejuvenated asphalt and SBSMA increased gradually. In contrast, the interfacial interaction energy between HDE rejuvenated asphalt and SBSMA decreased gradually. The fully restored SBS molecular structure had stable thermodynamic properties and could accelerate the diffusion effect of rejuvenated asphalt.