PNNL

Abstract

Self-healing asphalt technologies provide a sustainable approach to addressing the frequent repair needs of asphalt roads while reducing the environmental and economic burdens associated with repeated repairs. The self-healing performance of asphalt binders is influenced by the molecular characteristics of modifiers, particularly their polarizability, which affects intermolecular interactions, adhesion, and molecular mobility. This study examines the effect of algae-derived bio-oils with varying degrees of polarizability on the self-healing behavior of asphalt binders. The investigation combines experimental evaluation with Density Functional Theory calculations. The results indicate a strong correlation between polarizability and healing performance. All bio-oil-modified binders demonstrated higher polarizability than the unmodified control asphalt and exhibited improved self-healing. Among the tested bio-oils, the binder modified with ALG4 showed the highest healing index, which was approximately 2.5 times greater than that of the control. ALG4 also had the highest polarizability value at 219.4 Bohr³. The superior healing performance of ALG4 is attributed to its molecular composition, including octadecanamide and saturated fatty acids such as palmitic acid and stearic acid, which facilitate dynamic bonding within the asphalt matrix. Computational results further support this observation. Molecules such as oleic acid and n-hexadecanoic acid in ALG4 showed strong interactions with key asphalt components, with interaction energies ranging from -17.61 to -31.70 kilocalories per mole. These findings reinforce the hypothesis that higher molecular polarizability enhances molecular affinity and promotes healing. In addition to improved material performance, algae-based bio-oils offer notable environmental benefits. Replacing 6 percent of petroleum-based asphalt with algae-derived bio-binder has the potential to reduce net carbon dioxide emissions by 1.3 US tons of CO2-equivalent per lane-mile per year through material substitution. A further reduction of 1.2 US tons of CO2-equivalent per lane-mile per year can be achieved through extended pavement life enabled by enhanced self-healing. Thus, algae-based bio-oils present a dual environmental advantage by providing storage for atmospheric carbon sequestered during algae growth while also extending the service life of asphalt pavements. This chemistry-informed study demonstrates that modifiers with high polarizability, particularly those derived from algae, hold significant promise for the development of next-generation sustainable asphalt binders. This approach integrates improved self-healing capability with the carbon sequestration potential of algae-based materials, thereby reducing long-term environmental impact and the demand for nonrenewable resources.