Investigation on the influences of moisture on asphalts' micro properties by using atomic force microscopy and Fourier transform infrared spectroscopy

Plenty work has been done on asphalt's moisture susceptibility at macro scales. However, limited work was done at micro scale to aid in the understanding of interactions between asphalt and moisture. This paper uses atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR) to investigate the mechanism of asphalt property changes during water immersion. Six asphalt samples from same crude oils sources are prepared. Wet-conditioned samples were fabricated by immersing dry samples in water for 72 h. Samples' micro mechanical properties were obtained by AFM mechanical tests. Chemical alterations were detected by FTIR test. Results from AFM and FTIR tests are compared and analyzed. It is found that formation of asphalt microstructure is closely related to long chain index. Both microstructure and long chain index are less susceptible to water immersion when compared to matrix and other functional group indexes. AFM mechanical results show reasonable connections to FTIR results which indicates that polar components tend to interact with polar water molecules.