On the rheological behaviour of colophony rosin-based bio-binders for road pavements

Road pavements impact significantly on the environment, being directly responsible of an important proportion of greenhouse gas (GHG) emissions and air pollutants. In recent years, the pavement engineering industry is moving towards a more sustainable way of operating, in order to minimize the uncontrolled consumption of resources and tackle climate change. One of the most important challenges is to find viable, renewable, and eco-friendly alternatives for fully replacing (or partially replacing) the bitumen in asphalt pavements, while maintaining their overall performance unchanged and preferably reducing costs. To this end, a wide range of bio-based products and binders, wholly or partly derived from materials of biological origin, has been investigated, including bio-oils obtained from different sources of biomass (i.e., agricultural and forestry wastes, live-stock manure, microalgae), municipal wastes, and plant-based materials. Moreover, the latest studies confirm the feasibility of using waste products from the wood industry and vegetable or recycled oils for the production of completely bitumen-free binders for road pavements. Within this framework, this research focuses on the potential use of colophony rosin, a natural product obtained from the distillation of turpentine secreted by coniferous trees, blended with waste from food chains and polymers (virgin and recycled) to obtain a bitumen-free binder. Consequently, the properties of different bio-binder blending combinations are compared to conventional bitumen through empirical, rheological, and viscosity tests to assess the behaviour of the blends in a wide range of service temperatures, including asphalt production and laying operations. The findings of this study show that the bio-binder has promising properties that made it a suitable alternative to the petroleum-based binders used for road pavement construction.