Study on performance improvement of solvent asphalt based on microbial digestion

Solvent-based cold-mix asphalt features low energy consumption and reduced emissions but suffers from insufficient early-age stiffness due to slow solvent volatilization. This study proposes a biological enhancement strategy in which a hydrocarbon- degrading strain (Acinetobacter halotolerans) is applied to the binder surface to accelerate the removal of light hydrocarbons. Gas Chromatography–Mass Spectrometry (GC–MS) analysis shows that the microorganisms selectively digest C6– C9 hydrocarbons, significantly reducing the total solvent content, with enhanced efficiency when glucose is supplied as a co-substrate. Rheological measurements confirm that microbial digestion markedly accelerates stiffness development and improves high-temperature deformation resistance during curing. Fourier Transform Infrared Spectroscopy (FTIR) further indicates an increase in oxygenated functional groups, consistent with a compositional shift toward heavier fractions after microbial action. Minor softening effects from microbial metabolites were observed, but their influence on the overall mechanical response is limited. These findings demonstrate a sustainable and effective bio-assisted pathway to enhance the earlyage performance of solvent-based cold-mix asphalt.