A microstructural insight of modified bitumen using epi-fluorescence microscopy

Abstract

The widespread usage of polymer modified binders (PMBs) is due to the growing perception that they offer increased resistance to pavement distresses. The availability of inherently different modifiers has expanded the range of PMBs to select from when designing asphalt pavements. Correct blending of the polymerin bitumen remains an important requirement for optimal performance of PMBs. It is difficult to determine the polymer morphology by just measuring the physical properties of the PMB. This paper presents a microscopic technique that allows the use of high energy light (e.g. ultraviolet light or high-energy visible light) to excite and consequently cause the polymer-rich phase to fluoresce at a wavelength that can be detected by the eye. Epi-fluorescence microscopy can be used to differentiate between the bitumen phase (which does not fluoresce) and the polymer phase to show the polymer distribution/dispersion in the base bitumen. This is an important tool to characterise the in situ structural and chemistry effect of modifiers within bitumen in order to determine their influence on the modified binder performance. This paper shows that a sufficient degree of compatibility between polymer and bitumen is necessary in order to avoid separation during handling for the PMB to achieve the expected pavement layer performance.