| The cracking of asphalt concrete under fatigue load is the main reason that affects the service life of road.It is particularly important to have a thorough understanding of the cracking characteristics of asphalt pavement and improve its anti-fatigue cracking ability to extend the service life of road.Due to the increasing traffic volume,adding road modifier has become the main method to solve the high and low temperature stability of asphalt concrete.Butun rock asphalt is a kind of natural asphalt,which has been widely used in engineering practice in recent years because of its effective improvement of asphalt concrete performance.In this paper,the butun rock asphalt concrete and its control materials,the matrix asphalt concrete and SBS modified asphalt concrete,are taken as the research objects.The strain field and displacement field of the specimens are measured by the synchronous DIC observation technology of the three-point bending repeated loading test of the small beam,and the fatigue crack cracking characteristics are analyzed from the macro and micro point of view The fatigue life,damage degree and crack propagation of three kinds of asphalt concrete are analyzed.The results show that: under different road environment and different loading frequency,the order of fatigue life is SBS modified asphalt concrete > butun rock asphalt concrete > matrix asphalt concrete,butun rock asphalt concrete is more sensitive to the change of road speed;the damage resistance of butun rock asphalt concrete is significantly higher than that of matrix asphalt concrete,and it has experienced a long-term aging test The results show that the damage resistance of the specimens is significantly lower than that of the specimens after UV aging,the damage resistance of the specimens after UV aging is lower than that of the specimens after short-term aging,and the damage resistance of the specimens after salt freeze-thaw cycles is significantly lower than that of the specimens under freeze-thaw cycles;the damage degree of the same material under the same number of repeated loads decreases with the increase of loading frequency;compared with the other two kinds of asphalt concrete,the damage resistance of butun asphalt concrete is higher The improvement of anti damage performance of rock asphalt concrete is reflected in the whole life process of asphalt concrete;according to the comparative relationship between the occurrence of macro cracks and fatigue life,it is suggested that the maintenance time of butunyan asphalt concrete pavement should be no later than 70% of fatigue life;under the same repeated load,the anti fatigue cracking characteristics of three kinds of asphalt concrete increase with the increase of loading frequency,and the cracking rate is higher The results show that the crack growth rate decreases with the increase of loading frequency;under the effect of different road environment factors,butunyan asphalt improves the fatigue cracking resistance of asphalt concrete and slows down the crack growth rate of asphalt concrete;in the process of fatigue crack growth from micro crack to macro crack,increasing the driving speed can slow down the cracking and elongation It is significant to prolong the service life of road. |
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