This project developed and tested asphalt binders and mixtures reinforced with graphene nanoplatelets (GNP) as a multifunctional pavement material. Work in the initial phase of the project focused on evaluating the mechanical properties of GNP-reinforced asphalt binders and mixtures. It also resulted in the development of a detailed method for material preparation and a quantitative analysis of the effect of GNP on the mechanical properties of asphalt binders and mixtures. It was found that the GNP could be mixed with asphalt binders without major dispersion problems. Binder and mixture specimens prepared with different amounts of GNP were subjected to three types of mechanical tests: (i) a complex modulus test at room temperature, (ii) indirect tension creep and strength tests measuring the relaxation and strength properties, and (iii) a fracture test at low temperature measuring the fracture energy. These tests showed that the addition of GNP greatly enhanced the flexural strength of asphalt binders at low temperatures, moderately improved the creep stiffness, and had no adverse effects on relaxation properties. It was also observed that, compared with conventional asphalt mixtures, GNP-reinforced asphalt mixture specimens exhibited better cracking resistance in terms of strength and fracture energy. However, GNP addition did not improve the electrical conductivity of the asphalt materials. In the second and final phase, the compaction process of GNP-reinforced asphalt mixtures was investigated. This involved determining (i) the compaction effort in terms of the number of gyrations for a targeted air void ratio, (ii) the air void ratio that can be achieved for a given compaction effort, and (iii) the compaction temperature for a given compaction effort and target air void ratio. It was experimentally observed that the addition of GNP significantly reduced the number of gyrations needed to compact the mixtures to a target air void ratio. The reduction ranged from 15% to 40% for different mix designs. Furthermore, the GNP allowed successful compaction at a lower temperature. In parallel with compaction experiments, a series of rut experiments was performed on GNP-reinforced asphalt mixtures in collaboration with the Minnesota Department of Transportation. The addition of GNP was seen to lead to an improvement in the rut performance of the mixtures.
The final report is available.