Insights into the mechanism of modification by self-assembling starch-based fatty acid esters that cause a pronounced time-dependent effect on asphalt hardness

Modifying and controlling the viscoelasticity of asphalt is a major challenge for maintaining and managing paved roads and extending their life. To date, asphalt has been modified with petroleum-based synthetic polymers, mainly to improve its resistance to permanent deformation. While, we are developing an asphalt modifier, 2,3,4,6-O-tetrapalmitoylated-1,5-anhydro-d-glucitol (C16AG), which is obtained from starch and fatty acids as raw materials. Here, we performed various experiments to obtain insights into the mechanism of asphalt modification by C16AG. The results showed that the hardness of C16AG-modified asphalt showed a time dependence: it remained softer than the original unmodified asphalt for several hours after the addition of C16AG and then hardened depending on the amount of C16AG added. The time dependence of the hardness of the C16AG-modified asphalt is related to the modification mechanism and it is proposed to include the following processes: (1) C16AG mixes with the resin and asphaltene that usually cause the hardening of asphalt and (2) prevents the ordering of these components; (3) then spontaneous fiber network is formed slowly by C16AG.