Fatigue and healing properties of nano-reinforced bituminous binders

• Fatigue and healing properties of nano-reinforced bitumens were investigated.
• Effectiveness of additives was found to be highly dependent on blend composition.
• Analysis allowed self-healing to be distinguished from other artefact phenomena.
• Results were found to be coherent with nano-scale interaction phenomena.

The research work focused on fatigue and healing properties of bituminous binders containing carbon nanotubes (CNTs) and nanoclays (NCs) as reinforcing additives. Investigations were carried out by means of a dynamic shear rheometer and by employing specifically devised testing protocols. Experimental results were analysed with the specific goal of highlighting the role played by additive type and base bitumen. Although fatigue response of base bitumens was always improved by nano-modification, effectiveness of nano-particles was found to be highly dependent on the physico-chemical properties of blend components, which strongly influence the morphological configuration assumed by additives within bituminous media. Results obtained in healing tests were processed in order to discern between self-healing of cracks induced by fatigue damage and other artefact phenomena which are related to viscoelastic changes occurring in the bulk of the material. Outcomes of fatigue and healing tests were found to be coherent with interaction mechanisms which take place at the nano-scale.