Chemical and Rheological Evaluation of Aged Lignin-Modified Bitumen

Abstract

As bitumen oxidizes, material stiffening and embrittlement occur, and bitumen eventually cracks. The use of anti-oxidants, such as lignin, could be used to delay oxidative aging and to extend the lifetime of asphalt pavements. In this study, the chemical and rheological effect of lignin on bitumen was evaluated by using a single dosage organsolv lignin (10 wt.% dosage). A pressure aging vessel (PAV) was used to simulate the long-term aging process after performing the standard short-term aging procedure, and the lignin-modified bituminous binders were characterized by an environmental scanning electron microscope (ESEM), Fourier-transform infrared (FTIR) spectroscopy, and a dynamic shear rheometer (DSR). From the ESEM results, the uniform microstructure was observed, indicating that the addition of lignin did not affect the worm structure of bitumen. Based on the FTIR test results, lignin-modified bitumen showed that a lower number of carbonyl and sulfoxide compounds were generated after aging than for neat bitumen. Based on the linear amplitude sweep (LAS) results, the addition of lignin slightly reduced the fatigue life of bitumen. From the frequency sweep results, it showed that lignin in bitumen acts as a modifier since the physical interaction between lignin and bitumen predominantly affects the material rheology. Overall, lignin could be a promising anti-oxidant due to its economic and environmental benefits.

Evaluation of Organosolv Lignin as an Oxidation Inhibitor in Bitumen

“…The size of lignin powder, which was in the range of 20-200 µm, observed by an optical microscope and an environmental scanning electron microscope (ESEM, Eindhoven, Netherlands). The procedure to prepare the ESEM device and samples is discussed in [1]. The lignin powder was fixed on the specific sample holder plate with a black sticker sheet.…”

“…The carbonyl (C=O, 1700 cm −1 ) and sulfoxide (S=O, 1030 cm −1 ) compounds were analyzed as conventional aging indices for both neat bitumen and lignin-bitumen systems. The aging effect of lignin itself was not obvious or even negligible [1]. To eliminate the effect of lignin, as a material of high content of carbonyls and sulfoxides, the increase ratio index (IRI) was calculated by using the difference of the aging index under fresh and aged conditions, and the proportion of bitumen in the mix.…”

“…However, considering the uncertainty in crude oil supply, alternative binders is encouraged to be used as a replacement of bituminous binders or performance modifiers. Especially, lignin, among others, has attracted considerable attention as modifier [1,2] or substitute [3] of bitumen. Lignin is one of the most abundant natural polymers on Earth, with the total amount of lignin present in the biosphere estimated to exceed 300 billion tons and with an annual increase of approximately 20 billion tons [4].…”

“…In general, oxidation reactions in bitumen yield changes in its generic chemical composition and, finally, its colloidal structure, deteriorating the physicomechanical properties. Lignin has been found to retard bitumen oxidation [6][7][8][9], mainly due to the lignin radical scavenging activity, its polyphenolic structure [10][11][12] and the physical interaction between bitumen and lignin [1]. However, lignin itself also has a large number of carbonyl and sulfoxide functional groups, which should be taken into account separately from the bituminous functional groups that evolve due to the aging of bitumen [13].…”

Sustainable Designed Pavement Materials

“…Materials modification technologies are thus widely used in pavement engineering to improve the long-term performance of pavement materials. For instance, ethylene bis stearamide based graphene [17], styrene-butadiene-styrene latex [18], styrene-butadiene rubber [19], aged lignin [20] and bio-based polyurethane [21] were used as modifier and detailed explained in this special issue. The viscos-elastic behavior, storage property, fracture energy, rutting resistance, and anti-cracking property were presented.…”