Optimization of Properties and Resistance of Asphalt Roads using Nanotechnology
Against the backdrop of the sharp increase in the volume of heavy traffic in recent years and the consequences of climate change, conventional asphalts are increasingly reaching the limits of their performance. Plastic deformation, mostly in the form of rutting, and cracking due to material fatigue or the effects of cold, characterize road construction and cost billions of euros every year.
Decades ago, the use of polymer-modified bitumen (PmB) began to address these problems, which also resulted in a significant improvement in the performance of the layers produced with these binders. As a consequence, heavily loaded surface courses are now almost invariably built with PmB. However, the potential of this type of bitumen modification has been largely exhausted, so that new, innovative approaches must be pursued to meet future challenges.
In this context, the use of nanotechnology promises significant improvement. The mode of action of nanoparticles is essentially based on their extremely large specific surface area, which can be expected to have a positive effect on almost all asphalt properties. The addition of nanoparticles has already proven successful in cement-bound building materials, among others.
It is very likely that the addition of nanoparticles in bitumen leads to the formation of nano-composite-like structures, as known from polymer chemistry: Both the association polymers of pure bitumen and the added macromolecules can strongly adsorb on the surface of nanoparticles with suitably compatible surface, thus forming an adsorption boundary layer whose mechanical and thermal properties exceed those of the bulk material. Thanks to the large surface area of the nanoparticles, a small volume fraction of the particles in the material is sufficient to form sufficient adsorption boundary layer phase, so that the macroscopic properties of the resulting composites, such as viscosity, toughness, strength are improved. The viscosity of the material is increased simply by the presence of hard particles. Since inorganic nanoparticles are impermeable to solvents and gases, the barrier properties of the composites are also improved, making the ma-terial less susceptible to oxidation and attack by solvents (oil, gasoline, chemicals) applied to the road surface. A road surface based on such a composite should thus be much more durable and long-lasting than conventional road surfaces.
The aim of this research project is to develop novel composites of inorganic nanoparticles and bitumen for use in asphalt road pavements with improved durability. The aim is to improve the service properties of asphalt, to increase the durability of asphalt roads and to contribute to the improvement of environmental conditions, e.g. by saving energy and resources. The main task of the project is to develop and produce nanoparticle bitumen composites (NPBK) and to describe them by analytical and engineering bitumen tests with regard to the overall objective. In this context, it is to be investigated how and which NPBK can be used to improve the service behavior as well as to increase the durability of asphalt. The successfully tested NPBK are then to be investigated and optimized in asphalt mixtures as composite asphalt mixes in the laboratory. The optimized mix shall be manufactured, placed and evaluated on a large scale. The production technology and quality assurance of the NPBK for the considerable quantities required in road construction represent an accompanying work objective, as does occupational and product safety, in order to avoid adverse consequences for health, both during production and processing and, if necessary, during use as a result of abrasion.
From a scientific and technical point of view, the implementation of the project will provide important knowledge regarding the synthesis of novel functional polymers, the behavior and properties of the novel polymers and the interaction between polymers, nanoparticles and the solvent bitumen. Furthermore, the mechanical properties of the novel building materials can be used to create material models that can be used in dimensioning and prediction calculations, thus advancing analytical design.
Federal Ministry of Transport and Digital Infrastructure
Federal Highway Research Institute (BASt)
Dipl.-Ing. Lukas Renken (ISAC GmbH)
Dipl.-Ing. Dipl.-Wirt.-Ing. André Meyer