- 2018 Informa UK Limited, trading as Taylor & Francis Group This paper presents results on the evolution of the macroscopic appearance and surface microstructure of asphalt binders aged in an accelerated weathering tester. Two binders used in hot mix asphalt and two binders used in warm mix asphalt were aged in the presence of UV radiation, heat, oxygen and moisture. The same binders were previously aged using the same protocol but without the presence of moisture. Analysis of images captured using atomic force microscopy showed significant differences in the microstructure of binders aged in the presence of moisture versus those that were aged without moisture. There was no consistent evolution in the microstructure features in the presence of moisture. The combined effects of moisture and UV radiation caused part of the binder to become soluble and be transported away, while the remaining part of the binder experienced cracking and discontinuities. This observation relays the vital role that these atmospheric agents play in the degradation and microstructural evolution of asphalt binders.