Effects of lignin on the properties and performance of bitumen and hot mix asphalt

Abstract

This research program aims to investigate the effects of lignin addition, in powder and pellet form, on the properties of bitumen and performance of HMA. The incorporation process of different lignin contents into bitumen is investigated in order to select the parameters (temperature, speed and duration) of the incorporation process and to show the effect of each parameter on the stability and homogeneity of the modified bitumen. The incorporation process is evaluated by performing storage stability test and microscope observation. Afterwards, the rheological and chemical properties of lignin-modified bitumen are studied in detail by performing Brookfield rotational viscometer (BRV), dynamic shear rheometer (DSR), multiple stress creep recovery (MSCR), bending beam rheometer (BBR), full complex modulus (G*) and Fourier-transform infrared (FTIR) tests. The anti oxidative effect of the lignin on the aging properties of the lignin modified bitumen is also discussed. For HMA, shear gyratory compaction (SGC) tests are performed to examine the lignin effects on the compactability of modified HMA by using the wet and dry process. Following, the HMA performance is evaluated through a series of tests, including moisture sensitivity, indirect tensile strength (ITS), complex modulus (E*), rutting and thermal stress restrained specimen test (TSRST). The results show that the lignin is stable in bitumen and lignin is well dispersed and distributed over bitumen. The effect of incorporation temperature and duration on the stability and homogeneity of bitumen should be considered for high lignin content. Lignin powder increases the viscosity of the bitumen, stiffness at high and low temperatures and resistance to permanent deformation, while the pellets show different behaviour which is due to the presence of soybean oil that dilutes the bitumen. Lignin does not show anti oxidative aging properties of bitumen. For the HMA compactability, lignin increases the air voids content, while the tall oil decreases it. The wet process shows lower air voids than the dry process. Lignin improves the moisture sensitivity and rutting resistance of HMA. Lignin increases the stiffness of the bitumen and decreases the phase angle. Adding low lignin content does not show a significant change on the low temperature performance, while high lignin content reduces the resistance to thermal cracking. Overall, it is possible to replace part of the bitumen by lignin.

Date	14 Jun 2024
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Alan Carter (Supervisor) & Jean-Claude Carret (Co-supervisor)