Waste crumb rubber (CR) which is obtained from scrap tires can be successfully used as an asphalt binder modifier for the purpose of attaining the economic benefits with a desirable performance. The wet process was used in this study to investigate the rheological, morphological, and physical changes that would occurred to asphalt binder as a result of the interaction with different rubber contents, that is, 5, 7, 10, 12 and 25. The penetration, viscosity, softening point, ductility, Superpave performance grades, multiple stress creep recovery (MSCR) of the prepared modified binders were measured under different ageing conditions and temperature ranges. Furthermore, atomic force microscopy (AFM) scanning technique was also conducted in tapping mode to characterize the microstructure of these binders. The obtained results showed that as the rubber content increased, the viscosity and softening point values increased with a reduction in the penetration and ductility values. Rubber content of 10 was ranked as the higher percentage of rubber in terms of bumping the performance grade by at least two grades at high testing temperatures. The grading performance tests based on rutting index (G*/sin d°) and non-recoverable creep compliance index (Jnr) showed a comparable result for ranking the stiffer binder with a greater resistance to rutting. However, most of crumb rubber modified binders failed to meet the stress sensitivity criteria of MSCR test. AFM images can be considered as a new effective and suitable tool that should be adopted for further microstructural analysis. © 2021 Elsevier Ltd. All rights reserved.