Evaluation of the adhesion and healing properties of modified asphalt binders

The adhesion between asphalt binder and aggregate plays a fundamental role in the mixture's resistance to moisture damage and fatigue cracking. And self-healing is another inherent property of asphalt binder which is related to the mixture's durability. Many efforts have been taken to understand those individual properties, while few research focuses on evaluating the adhesive property of binder-aggregate system incorporating the effects from binder's self-healing, especially for the modified binders that is expected to improve the mixture's durability. In this study, a modified binder bond strength (BBS) test procedure including a sample healing setting was employed to evaluate the compound effects of adhesion and selfhealing property of five representative modified asphalt binders with varies modifiers at several dosages. The results show that the linear styrene-butadienestyrene (SBS), high-density polyethylene (HDPE), crumb rubber, and terminal blend (TB) crumb rubber modified binders have negative effect on bonding strength of binder-aggregate system without considering their self-healing properties. However, the recovery of pull-off tensile strength (POTS) of the HDPE and crumb rubber-modified binders after several failure-healing cycles exhibit significant higher ratios than those of base binder and SBS/TB crumb rubber-modified binders which are similar at their optimum dosages. Furthermore, the measured bonding-strength recovery capability of tested binders has a very well correlation with their mixtures' fatigue performance determined by the four-point beam (4PB) fatigue tests. This indicates that the proposed method can provide a better understanding of pavement performance of modified binders In addition, the Fourier transform infrared spectroscopy (FTIR) test was conducted to study the mechanism of modifiers on improving long-term adhesive behavior of the binders in terms of chemical response. It is found that the methylene plus methyl hydrogen to carbon (MMHC) index of FTIR spectrum of modified binders has a control on their self-healing and the aggregate selective adsorption of their long-chain molecules, and it shows a good agreement with the bonding-strength recovery ratios. (C) 2020 Elsevier Ltd. All rights reserved.