Valorisation of Pulp and Paper Industry Wastes—Incorporation in Bituminous Mixtures for Road Construction

Some wastes from the paper pulp production process are still sent to a controlled waste landfill. These materials can constitute alternative resources for constructing road pavements. The study aimed to characterize and explore the sustainable application of two inorganic wastes resulting from the paper pulp process, the dregs (green liquor wastes) and the grits (slaker wastes), in the production of bituminous mixtures by the analysis of samples prepared with 5 and 10% of dregs and 5 and 10% of grits on the baseline reference bituminous mixture AC 14 surf 35/50. Some relevant mechanical properties of the blends were assessed based on Marshall compression, sensitivity to water and wheel-tracking tests. Additionally, water poured on the loose asphalt and compacted slabs’ surface was analysed to determine the portion of harmful chemical compounds leached from the asphalt material. The results show that using dregs presented some technical limitations related to mechanical performance and that the incorporation of grits has an acceptable mechanical behaviour. Moreover, the study shows that the measured leachate resulting from water flow in a reference asphalt mixture and the blends with grits are insignificant. It can be concluded that using grits in asphalt mixtures is a promising technique regarding mechanical behaviour and environmental impacts that need further studies.