Experimental Study On The Microstructure And Self-healing Performance Of Asphalt Mortar Under Heat Aging

With the development of our country’s social economy,the road transport industry formed by urban roads and roads has developed by leaps and bounds.In the whole road network,the vast majority of the asphalt pavement.And asphalt pavement in the early use will appear some small cracks and damage,long-term use process,coupled with some of the surrounding complex environment,leading to the decline of the road surface fatigue life and performance.In fact,the existing research results have confirmed that the asphalt material has certain degree of fatigue damage healing ability,asphalt and asphalt mixture damage healing performance research has received wide attention from foreign road research workers.In order to study the self-healing ability of asphalt mortar after thermal aging,and its self-healing mechanism,In this paper,we consider three kinds of asphalt binder,which is commonly used in the Inner Mongolia area,matrix asphalt,SBS modified asphalt,crumb rubber modified asphalt and filler combination with the formation of asphalt mortar after aging under the influence of the external environment,the damage and healing characteristics of asphalt materials were investigated by macro and mesomechanical tests,the main factors influencing the healing were explored,and the evaluation indexes of injury self-healing were found,which provided the reference for the design and improvement of asphalt materials.Atomic force microscopy(AFM)was used to reflect the change of microstructure of asphalt mortar under heat aging,the experiment results show that matrix asphalt mortar appears obvious "bee-like structure",with the increase of aging degree,the "bee like structure" gradually became narrower and longer,the larger the filler-asphalt ratio will weaken the aging of the asphalt mortar;SBS modified asphalt mortar does not appear "bee-like structure",the effect of aging on SBS modified asphalt mortar is less than that of the matrix asphalt mortar,the addition of SBS modifier will play an important role in inhibiting the aging of asphalt mortar,the surface of crumb rubber modified asphalt mortar is rough,and there is no "bee-like structure",which shows the phenomenon of molecular aggregation and association after long-term ageing.Fatigue test and fatigue-healing-refatigue test of asphalt mortar were carried out by dynamic shear rheometer(DSR),self-healing performance was evaluated by healing rate and energy methods,combined with Leica microscope on the self-healing situation of mesoscopic observation,The results shows that fatigue life has increased after the aging of the asphalt mortar,modified asphalt mortar has better anti-fatigue performance,the appropriate increase in the filler-asphalt ratio can improve the anti-fatigue properties of asphalt mortar.The self-healing properties of matrix asphalt mortar and SBS modified asphalt mortar are better than that of crumb rubber modified asphalt mortar,in the case of less damage,the higher the healing temperature,the longer the intermittent period,the better the healing effect,the effect is the worst when the filler-asphalt ratio is 1.5,and aging will reduce the self-healing effect of asphalt mortar.Bending beam flow meter(BBR)was used to test the low temperature bending rheology and thermal induction self-healing of asphalt mortar,the results show that the most important influence on the rheological properties of asphalt mortar is the asphalt-filler ratio,followed by the type of asphalt,the degree of aging is less affected,the low temperature cracking resistance of asphalt mortar can be reduced by increasing of the asphalt-filler ratio and the thermal aging,with the increase of the asphalt-filler ratio and the aging degree will make the self-healing performance worse.The higher healing temperature and the longer healing time,the better self-healing performance of the asphalt mortar,crumb rubber modified asphalt mortar has better self-healing properties at low temperature performance.It is suggested that the rubber powder modified asphalt mortar with relatively small filler-asphalt ratio is used as pavement material in cold area.