Presentation av masterarbete Jakob Fornman

A Labaratory Ageing Method for Lignin-Integrated Asphalt


Climate goals in industry are a powerful driving force in the development of new industrial processes. The Swedish Transport Sector has setup the goal of becoming CO2 neutral by the year 2045. Thus, the asphalt industry must develop more sustainable materials and processes. Lignin has the potential to act as an extender to the asphalt binder as well as an antioxidant with radical quenching potential. This thesis will therefore investigate the impact lignin has on the asphalt throughout its service life. A method for simulating the accelerated ageing behaviour of asphalt pavements with the binder bitumen, partially replaced with lignin, was therefore designed and evaluated. The thesis includes a literature study and an experimental trial. First, the literature study was conducted in order to find the factors and mechanisms, leading to ageing in asphalt pavements as well as methods for ageing asphalt samples in a laboratory setting. The review found the ageing behaviour for in-field asphalt is the long-term ageing in which, oxidation is the main ageing mechanisms. Thus, most ageing methods use elevated pressure or temperature to accelerate the oxidative behaviour.

In the experimental part the long-term oven test was selected as the ageing method. Thus, three batches of asphalt were produced: in two of the batches lignin was integrated into aggregate mix to reduce the bitumen content. Hence, the batches contained 10 wt% and 25 wt% lignin by binder weight respectively. The third batch was a conventional asphalt pavement used as a reference. All three batches were analysed when both aged as well as when non-aged using Cantabro Mass Loss, Prall and the Indirect Tensile Strength Ratio to assess the impact ageing has on the mechanical properties of asphalt. Furthermore, bitumen from all batches were separated from the aggregate mixture in order to evaluate the binders with softening point test and infrared spectroscopy. Results from the IR spectroscopy verify the efficacy of the ageing method. Oxidation has occurred on all aged samples. Furthermore, the softening point test verified the hypothesis from the literature review in that ageing lead to increased stiffness in binders from all asphalt samples.
The mechanical testing displayed interseting findings. All asphalts showed a deterioration in the Cantabro test after ageing. Hence, the asphalts are less ductile. In the Prall test both lignin batches improved their abrasive resistance after ageing whilst, the opposite was observed in the reference batch. Lastly, the indirect tensile ratios decreased from ageing in all samples.

Examinator: Gunnar Westman

Opponent: Victor Lunai