Improving Bitumen Properties with Chitosan: A Sustainable Approach to Road Construction

This research explores the utilization of chitosan, a naturally derived biopolymer, as an innovative additive in bitumen for road construction. The experimental procedure for incorporating chitosan into bitumen, in agreement with its thermal stability, is described. Four different types of chitosan (two different degrees of deacetylation: >75 and >90% in free amine groups; molecular weight ranging from 100 to 800 kD) have been considered. Each chitosan was added to a bitumen at 1, 3, 6 wt%, and the mechanical characteristics were tested by dynamic shear rheology with the aim of testing the thermal stability of modified bitumen. An increase in the gel-to-sol temperature transition was generally found in the presence of chitosan, suggesting enhanced resistance to deformation under traffic loads. The most marked effect was obtained for chitosan with a molecular weight of 310,000–375,000 kD and with a deacetylation degree ≥75% (free amine groups). In addition, it was found that chitosan can slow down the oxidative aging of bitumen, especially when chitosan with high molecular weight (600,000–800,000 kD) and with a deacetylation degree >90% (free amine groups) was used. This further finding suggests that chitosan can potentially extend the final road pavement life.