Investigation Of The Effect Of Secondary Ageing On Self-Healing Performance Of Asphalt Mortar

As a viscoelastic road material,asphalt can revocer the damage by its self-healing properties,thereby extending its service life.The asphalt will,however,continue to degrade over time,which will affect both the road’s performance and its ability of self-healing.Insufficient study has been done on the self-healing capabilities of both recycled and aged asphalt materials,though lots of researches have been done on the conventional features such as the fundamental physical properties and rheological properties of ageing asphalt pavement.In this study,asphalt mortar was used as the research subject.Using fatigue-healing-fatigue,fracture-healing-fracture,the self-healing characteristics of mortars at various stages,such as primary ageing,regeneration,and secondary ageing were systematically studied.Firstly,an asphalt slurry was created by mixing 70#asphalt,SBS modified asphalt,and aged asphalt recycled from RAP.Then,using various techniques,such as penetration level,softening point,rotational viscosity,infrared spectroscopy,dynamic shear rheological test,etc.,the effects of secondary ageing on the conventional properties and rheological properties of the asphalt and mortars were investigated.The findings show that secondary ageing process drastically reduces the asphalt’s fundamental physical qualities while also causing the regenerating agent failure.After the second ageing,the asphalt mortar gradually becomes harder,its high-temperature stability improves,and none of the samples’ fluidity can get close to that of Newtonian liquid.Although SBS modifier can,to a limited extent,prevent the development of sulfoxide and carbonyl groups and improve the anti-aging properties of asphalt,SBS modifier degrades further during the secondary ageing process,which improves the flow ability of SBS-modified asphalt slurry.Secondly,to explore the self-healing characteristics of various asphalt mortas at medium and low temperatures,the fatigue-healing-fatigue and fracture-healing-fracture test techniques were used.According to the test results,different asphalt mortar fatigue self-healing and fracture self-healing abilities are worser after secondary ageing than that of after first aging process.Additionally,the SBS-modified asphalt mortar prsent a much smaller reduction in healing index than that of the 70#asphalt motar.Additionally,asphalt mortar still exhibits strong fatigue self-healing capability after secondary ageing,although it is challenging to recover this performance after low-temperature fracture.Finally,a self-healing performance prediction model for asphalt mortar was built based on the BP neural network.The findings indicate that using the BP neural network model,it is possible to predict the self-healing performance of various asphalt mortars under the given healing time and healing temperature.The fitting degree of the test results is over 0.9,the model has a high agreement with the actual value,and its error value in prediction verification is low.