Void distribution, interfacial adhesion and anti-cracking mechanisms of cold recycled asphalt mixture based on AFM and X-ray CT

To reveal the anti-cracking mechanisms of cold recycled mixture (CRM) prepared by waterborne epoxy resin/styrene butadiene rubber latex (WER/SBR) modified emulsified asphalt (EA), the void distributions in CRM were analyzed by X-ray computed tomography. Then a method for calculating the adhesion work of asphalt-aggregate interface was proposed based on atomic force microscope tests. Finally, the anti-cracking properties were discussed by low-temperature bending and semicircular bending fatigue tests. Results indicated that the surface void contents of CRM specimen were all smaller in the middle and larger at both ends along the height direction. The WER/SBR modifier exerted a significant filling effect on the voids, reducing the void content and size. Moreover, WER/SBR modified EA (WSEA) showed stronger adhesion property and deformation resistance. WSEA-fresh aggregate interface had the largest adhesion work of 267.25 mJ/m2. Further, the interfacial adhesion failure between EA and fresh aggregate, as well as the cohesive failure of the syncretic interface between EA and aged asphalt were the main cracking forms of CRM specimen. A three-dimensional network in the WSEA-aggregate interface was formed by the WER/SBR modifier, improving the interfacial adhesion property. The void distributions and interfacial adhesion property in CRM specimen significantly affected the cracking resistance.