Valorisation of lignin-rich industrial byproduct into half-warm mix reclaimed asphalt with enhanced performance

To promote a circular economy and sustainable development, the possibility of using a lignin-rich industrial byproduct as a partial substitute for asphalt emulsions in road pavements is analysed. A half-warm mix reclaimed asphalt (HWMRA)-type AC 16 surf S, manufactured with 100% reclaimed asphalt pavement, is selected. Substitution percentages of 0% (control mixture), 5%, 10%, 15%, and 20% are employed. The microstructure of the blend of the byproduct and asphalt emulsion is observed using scanning electron microscopy. The water resistance of the mixture is investigated using indirect tensile tests, as well as its volumetric properties. The stiffness, thermal susceptibility by indirect tensile tests, and resistance to permanent deformation by confined uniaxial compression tests and Hamburg wheel tracking tests are also studied. The optimum percentage of byproduct substitution is 5%, resulting in an enhanced HWMRA with a slightly better water resistance, higher resistance to permanent deformation at low and medium environmental temperatures, and higher indirect tensile strength and stiffness than those of the control mix.