Peter Mikhailenko

Observation of asphalt binder microstructure with ESEM

The observation of asphalt binder with the environmental scanning electron microscope (ESEM) has shown the potential to observe asphalt binder microstructure and its evolution with binder aging. A procedure for the induction and identification of the microstructure in asphalt binder was established in this study and included sample preparation and observation parameters. A suitable heat‐sampling asphalt binder sample preparation method was determined for the test and several stainless steel and Teflon sample moulds developed, finding that stainless steel was the preferable material. The magnification and ESEM settings conducive to observing the 3D microstructure were determined through a number of observations to be 1000×, although other magnifications could be considered. Both straight run binder (PG 58‐28) and an air blown oxidised binder were analysed; their structures being compared for their relative size, abundance and other characteristics, showing a clear evolution in the fibril microstructure. The microstructure took longer to appear for the oxidised binder. It was confirmed that the fibril microstructure corresponded to actual characteristics in the asphalt binder. Additionally, a ‘bee’ micelle structure was found as a transitional structure in ESEM observation. The test methods in this study will be used for more comprehensive analysis of asphalt binder microstructure.

Observation of bitumen microstructure oxidation and blending with ESEM

There have been a several studies observing bitumen microstructure using the environmental scanning electron microscope (ESEM); however, these have been few and far between. Nevertheless, there have been findings that show microstructure under ESEM clearly evolving with bitumen ageing. The objective of this paper is to focus on sample conditioning, oxidation and blending. A conditioning procedure was produced and the effect of freezing (−18°C) on the bitumen microstructure for 19 h was examined. A straight-run PG 58-28 bitumen was sampled, with the same bitumen being oxidised using hot air. Additionally, these two bitumens were mixed at ratios of 25/75, 50/50 and 75/25. The microstructures were compared with ESEM observation for their relative density, organisation and fibril size, clearly showing an evolution in the microstructure with oxidation and with different blending ratios.

ESEM Microstructural and Physical Properties of Virgin and Laboratory Aged Bitumen

The physical and microstructural properties of four straight run asphalt binders were examined and compared in virgin state and in after short term aging (RTFOT) and long-term (PAV) laboratory aging. RTFOT aging was conducted at 123, 143 and 163 °C. Physical testing parameters included penetration and softening point. Selected binders came from four different sources with same penetration grade. They all showed an increase in stiffness with aging, and RTFOT temperatures. The microstructural evolution of the binder was examined by Environmental Scanning Electron Microscopy (ESEM) on aged binders at 123 and 163 °C. The physical transformation corresponded to an evolution in the binders’ ‘fibril’ microstructure under ESEM as a result of electron beam exposure, with the microstructure getting denser with PAV aging. The asphalt binders showed varied ESEM ‘fingerprints’ and aged in different ways. The ESEM properties generally showed to evolve with the physical properties, although this was not the case for all of the binders due to their unique aging characteristics.

Recycled bio-sourced glycerol and diglycerol for asphalt release agents (ARA)

The objective of this study is to develop bio-sourced waste chemicals for use as asphalt release agents. Glycerol was extracted from bio-sourced waste and transformed by transesterification into the surfactants undecenoates of glycerol (MUG) and undecenoates of diglycerol (MUDG). They were composed of glycerol, monoglycerol, diglycerol, triglycerol, tetraglycerol and water. The formulations were mixed separately with water at quantities of 5–50%, along with acetone and commercial bio-sourced ARAs in order to observe the effects. The formulations were subjected to performance testing with the asphalt slide test, finding significant reduction in adhesion for a number of different formulations. The interaction of the formulations with bitumen was tested by the bitumen degradation test, which was combined with FTIR–ATR analysis, finding that the formulations do not dissolve the bitumen, but rather were adsorbed by the bitumen. The effects on asphalt mix of the best performing formulation, MUG at 20% in water, was tested by indirect tensile strength, determining that the formulation was acceptable for use in the field.

Recommendations of RILEM TC 252-CMB on the Effect of Short Term Aging Temperature on Long Term Properties of Asphalt Binder

The Rilem Technical Committee on Chemo Mechanical Characterization of Bituminous Materials has investigated the effect of short term aging temperature on long term properties of asphalt binder, chemically, physically and microstructurally. The increased use of warm mix asphalt (WMA) technologies warrants such investigations in order to validate laboratory aging procedures. To this end, penetration, softening point, Fourier Transform Infrared Spectroscopy, dynamic shear rheology (DSR) and electron microscopy (ESEM) were used. The experimental results on binders and warm (WMA) and hot (HMA) mixtures from nine participating laboratories indicate that the binder source, as well as method of evaluation, result in different rankings and behaviors among the four binders used. The TC recommends the development of appropriate RTFOT aging temperatures for the simulation of binder aging in WMA.

Protocol for the morphology analysis of SBS polymer modified bitumen images obtained by using fluorescent microscopy

ABSTRACT Fluorescent technique has been used to characterise the morphology of polymer modified bitumen for years. However, the main problem of this technique is a missing standardised protocol for image capture factors and processing algorithms (CF&PA). The purpose of this study was to find out the effects of CF&PA on morphology and set up a protocol for morphological analysis of SBS polymer-modified bitumen (PMB) using the fluorescent microscopy technique. In order to set up this protocol, fluorescent images were captured and processed with different CF&PA. Capture factors mainly include magnification, exposure time and storage format while processing algorithms include noise reduction, enhancement and segmentation. Morphological and parametric analysis indicated that all images must be captured under the same exposure time and should not be processed by white balance. Besides, four principles should be followed to determine the optimal magnification. As to the image storage format, JPEG 2000 was selected to retain the most details. The proper neighbourhood level was obtained from the particle number curve to realise noise reduction. Compared with other complicated segmentation algorithms, threshold methods are more suitable because of the typical two-phase characteristic of PMB. Because of potential change in detailed information of original images, enhancement was not recommended. Finally, the image capturing and processing steps and their levels were given based on the discussion above.