The effects of Kraft lignin on physical, rheological and anti-ageing properties of asphalt binders

One of the major concerns of infrastructure engineering is related to improve the quality and durability of asphalt pavements, and because of its large availability and antioxidant properties, the lignin, a biopolymer and byproduct from pulp and paper industry, have been tested as an additive for asphalt mixtures through the last years. The objective of this work is to properly mix Kraft lignin with asphalt binders, and to evaluate the effects on the physical, rheological and anti-ageing properties of the binders. The samples were submitted to penetration, softening point, Brookfield viscosity, and elastic recovery tests to evaluate the material’s consistency and elasticity. Then, they were aged through RTFO test, and analyzed by DSR to evaluate the rheological properties and by FTIR to measure the level of oxidation suffered. The tests showed that, in general, lignin increased the consistency of the material, but suggested a beneficial effect against oxidation and also increased the binder’s elasticity and its resistance to plastic deformations.