Performance evaluation of stone mastic asphalt (SMA) containing reclaimed asphalt (RA) and biopolymer lignin

To reduce environmental impact, it is necessary to replace fossil-based materials with renewable bio-based materials. The interest in using lignin as partial replacement for bitumen has significantly grown over the recent years. Lignin is the second most abundant natural polymer surpassed only by cellulose and it’s the byproduct of several industries. Moreover, the use of reclaimed asphalt (RA) in asphalt mixtures reduces the environmental impact associated with a decrease in the consumption of virgin and nonrenewable materials. Although most agencies allow RA to be used in many asphalt mixture types, it has not been common to use of RA in stone mastic asphalt (SMA) mixtures. This study evaluates the performance of SMA mixtures incorporating 30 % reclaimed asphalt (RA) and partially replacing 30 % of the virgin bitumen with biopolymer lignin. It includes a comprehensive analysis of hydrolysis lignin, kraft lignin, and lignosulfonate along with extracted binder testing and performance testing of asphalt mixtures. Lignin analysis revealed substantial differences in purity and composition, highlighting the unsuitability of lignosulfonate for asphalt applications due to its high sulfur and ash content. Binder testing showed that binder with hydrolysis lignin performs similarly to the reference polymer-modified binder while kraft lignin increases hardness and reduces low-temperature properties and elasticity. Performance testing indicates that SMA mixtures with 30 % RA can achieve results comparable to reference mixtures when a recycling agent is used. SMA mixture with hydrolysis lignin demonstrates superior performance over kraft lignin, particularly in terms of flexibility, low-temperature cracking resistance, and fatigue resistance. The study also shows that asphalt mixtures containing RA and hydrolysis lignin can be successfully recycled without performance issues if the reduced polymer content in the RA is properly compensated. The use of RA and hydrolysis lignin in SMA proves to be a promising and sustainable solution for producing high-performance SMA mixtures.