In this project, an innovative methodology is developed by using Laser Scanning Confocal Microscope (LSCM) to investigate the behaviour of bituminous binders and mortar under specific physical and mechanical conditions including the impact of several additives. Bitumen, an oil derivate, is an important binder used in asphalt mixtures, roofing materials and emulsions. Regarding the circular economy, a higher recycling rate and increased service life is expected for future application, as it provides both economic and ecological benefits: a base layer with 40% reclaimed asphalt is about 25% cheaper and its total environmental impact is reduced by 6% (based on an LCA-study). An increased service life and quality avoids mobility problems, damage, fast deterioration etc. In most cases, both aspects are proven by mechanical tests in laboratory. However, efficient use of this material demands more and more scientific insight in the fundamental structural behaviour of bitumen. In order to enhance the current sustainability vision of 'closing loops', besides the mechanical properties, also the physico-chemical aspects must be taken into account, especially
for higher recycling rates, fibre reinforcement, and additives improving healing and fatigue resistance. Moreover, both the development of innovative technologies, such as smart fibres in bitumen, and understanding the behaviour of the bituminous mixture, e.g. the ageing mechanism, need validated physico-chemical models.
In this project, both methodologies, mechanical and physico-chemical aspects, are used to investigate the properties of the same bituminous samples (bitumen and mortar). A new technology is introduced and validated: the latest Laser Scanning Confocal Microscope (LSCM) allows for measurements across a 50 mm area with nanometre resolution (5 nm in Z-direction and 10 nm in the XY-direction). This technology allows to scan quickly (5 s measurement time) the bitumen surface in order to visualize
aspects like bee structures (wax content) and bitumen coverage (adhesion between binder and granulate). Furthermore, the surface profile and film thicknesses are measured as well, which is important in the analysis of bitumen blending. Lastly, by combining these qualitative images with the Digital Image Correlation (DIC) methodology, it will be possible to obtain detailed quantitative results
and to track changes in the bituminous mixture on a nanometre scale, e.g. during blending or healing. This technology will be used, together with mechanical tests (Dynamic Shear Rheometer, Direct tensile tests, Fraass bending point) to investigate the ageing/healing process, blending of old and new bitumen during recycling, and optimized use of additives, such as fibres, crumb rubber and rejuvenators.
The project is divided into three steps:
- integration of this new high-tech equipment, especially adjusted for bitumen research, in our bitumen laboratory, including Matlab software for data analysis;
- development of a methodology for testing bituminous samples using an LSCM to fully understand bitumen morphology and physico-chemical mechanisms, related to ageing/healing, improved use of additives and as verification for mechanical tests. An opensource
database of 6 binders, containing the physico-chemical and rheological properties, will be available and a secured database with the special binders will be available for collaborative research.
- valorisation trajectories for designing new materials in a bituminous matrix, such as smart fibres or enhanced crumb rubber modified bitumen.