Optimisation of self-healing properties for asphalts containing encapsulated oil to mitigate reflective cracking and maximize skid and rutting resistance

Abstract

It has been proven that the addition of encapsulated bitumen rejuvenators into the asphalt mixtures can improve their natural self-healing properties, prolonging their lifespan. However, in order to use Ca-alginate capsules as an additive for self-healing roads, they must not reduce the performance properties of the pavement. This paper presents the results of a multivariable experimental study that aims to select the capsule size and strength that optimise the asphalts self-healing properties for mitigating reflective cracking, skid resistance, fatigue durability, deformation under loading (rutting) and the amount of oil released in the bitumen. The capability of the encapsulated bitumen rejuvenators to mitigate the reflective cracking effect was assessed by reproducing the traffic-induced reflective cracks in stone mastic asphalt mixtures. Cyclical loading tests were carried out using a laboratory wheel tracker to analyse the fatigue durability, self-healing properties and rutting effect. Furthermore, computerised tomography scanning technology was used to analyse the changes in the internal structure of the capsules inside the asphalt. Finally, Fourier-transform infrared spectrometry was applied to measure the amount of oil released by the capsules. It was concluded that (i) the oil released does not influence the skid resistance, (ii) capsules delay reflective cracking of asphalt and (iii) rutting increases proportionally to the oil released.