Lignin-Modified Asphalt: A Circular Approach to Infrastructure

To explore sustainable solutions in road construction, a team of Latvian and international partners conducted a comprehensive study “Performance evaluation of stone mastic asphalt (SMA) containing reclaimed asphalt (RA) and biopolymer lignin” on stone mastic asphalt (SMA) incorporating both reclaimed asphalt (RA) and lignin – a biopolymer derived as a by-product of wood processing.

The study is published in the Q1-ranked journal Construction and Building Materials and co-authored by Dr. chem. Jevgenija Ponomarenko and Ph.D. Aleksandrs Aršanica. It was carried out as part of the project “Development of sustainable bioasphalt mixtures with renewable biopolymer lignin”, funded by the Recovery and Resilience Facility (RRF).

What Did the Study Reveal?

Researchers investigated the possibility of replacing 30% of fossil-based bitumen with different types of lignin, while simultaneously incorporating 30% reclaimed asphalt in SMA mixtures. Key findings include:

• Commercial sulphur free enzymatic hydrolysis lignin (from hardwood biomass) showed good compatibility with bitumen, improving elasticity and low-temperature cracking resistance.
• Kraft lignin (from softwood pulp) increased stiffness but reduced elasticity and fatigue performance.
• SMA mixtures containing RA and hydrolysis lignin maintained or even improved performance compared to conventional mixtures – demonstrating better water resistance, deformation resistance, and low-temperature durability.
• These mixtures can be recycled again, provided that reduced polymer content is compensated.

Broader Context:

Air Pollution and Health

According to the World Health Organization (WHO), air pollution contributes to around 6.7 million premature deaths annually worldwide, and over 239,000 deaths in the EU alone due to PM₂.₅ exposure (WHO, EEA).

Using recycled materials and bio-based resources in asphalt production can significantly reduce emissions and associated health risks.

Climate Resilience and Resource Sustainability

The European Environment Agency (EEA, 2024) stresses the need to build climate-resilient infrastructure using biomaterials and circular economy approaches. The SMA developed in Latvia using RA and commercial lignin offers a practical example of this strategy in action.

Less Waste, Fewer Fossil Resources

Road construction consumes vast amounts of resources (ETC-CA, 2024). This study demonstrates that incorporating lignin and reclaimed asphalt (RA) into asphalt mixtures can significantly reduce CO₂ emissions and lower the use of fossil-based raw materials. It also helps to minimize the release of harmful gaseous emissions during bitumen application and reduces overall waste generation. Importantly, these improvements are achieved while maintaining – and in some cases even enhancing – the mechanical performance and quality of the asphalt.

The research is published in Construction and Building Materials, a Q1-ranked journal (JCR, Clarivate) in both Construction & Building Technology and Engineering, Civil categories.