Investigating the evolution of emulsified binder nanorheology using Atomic Force Microscopy

This study involves evaluating the evolution of rheological and nanorheological properties of asphalt emulsion residue and its control binder through the application of two different test methods, Dynamic Shear Rheometer (DSR) and Atomic Force Microscopy (AFM). This study also involves evaluating chemical properties by application of Fourier Transform Infrared Spectroscopy (FTIR). The adopted methods use the same evaporative techniques to recover the residue but involve different consecutive curing periods (procedure A: 24 hours at 25 degrees C and 24 hours at 60 degrees C and procedure B: 6 hours at 60 degrees C in a forced draft oven based on ASTM specifications). The evolutions of rheological properties have been investigated as the emulsion transitions through various degrees or stages of aging. Furthermore, the impact of aging in terms of its thermal history on the bitumen microstructure is reported. It was observed that certain asphalt chemical parameters have a consistent and measurable effect, as determined by the AFM, on bitumen microstructure. This study focuses on evaluating whether the full recommended curing periods are required and identifying the causes of different behaviors relative to base binders. Results indicate that oxidative aging contributes different to the change in rheology and nanorheology with various times of curing, compared with unaged base binder.