Determining the effect of ageing of nano-clay modified bitumen using atomic force microscopy

Abstract

The present study aims to evaluate the effects of ageing simulation on the physical properties of Nano-Clay Modified Bitumens (NCMBs). Bitumen with the penetration grade of 60/70 is modified with 0, 2, and 4% nano-clay, and the consistency of the samples is characterized using the penetration, softening point, and viscosity tests before and after aging. Atomic Force Microscopy (AFM) was employed to evaluate the surface roughness and tip deection of the modified bitumens. The results of the consistency tests revealed that incorporation of nano-clay up to 4% NC resulted in increased hardness of the modified bitumen, and all the modified bitumens were affected by ageing. Of note, the results from surface roughness and tip deection showed a similar trend, while 2NCMB exhibited the lowest roughness and highest tip deection. However, the results of the consistency tests and AFM conducted on ageing sensitivity of the bitumens were different, indicating that incorporation of nano-clay had an effect on the modified bitumen, but not on the unmodified bitumen. There was a high correlation between the results of consistency tests, surface roughness, and tip deection, indicating that AFM could identify any changes in the uidity of the bitumen. However, the correlation between the tip deection and penetration was tenuous.