Aging of asphaltic binders investigated with atomic force microscopy

We investigated the short and long term aging of asphalt cement (AC) with different AFM techniques (topography, phase and friction imaging and nano-indentation experiments). The aging process induces a growth and nucleation of the asphaltene micelles with a concomitant reduction of the maltene phase, whereas the short term aging induces the formation of fractal-like micellar structures. The friction investigation shows that the aging processes reduce the binder friction coefficient by 50%, and this reduction occur predominantly during the short term aging, while the growth of the micelles occur predominantly during the long term aging. The micro-indentation experiments revealed that the aging processes cause a stiffening of the AC film (half-order of magnitude for short term aging, and one order of magnitude for long term aging). The aging process also increased the apparent viscosity of the AC films by half-order of magnitude.