Experimental Study On Damage Healing Properties Of Aged Asphalt Binder

Fatigue cracking is the main cause of cracking,looseness,potholes and even base damage of asphalt pavement.The healing properties of asphalt binder have an important impact on the fatigue performance of asphalt.Studying the healing properties of asphalt binder for asphalt pavement maintenance and Conservation is of great importance.At present,the test method for the damage healing property of asphalt binder is asphalt fatigue damage test,and the evaluation index is the complex shear modulus.However,the recovery of modulus does not mean the recovery of the same degree of fatigue life.The research on the influencing factors of the existing asphalt binder healing performance is still relatively small and not deep.This paper attempts to provide a new test method and evaluation indicators to study the effect of aging on the damage healing properties of different types of asphalt binders.?1?Through the secondary infusion of asphalt samples to simulate the internal damage of asphalt,the maximum tensile force and ductility product based on the results of asphalt ductility tensile test were proposed as the evaluation index of asphalt interface healing degree.The interface healing of different temperatures,healing time,chemical reagents and second infusion of different kinds of asphalt was studied.The research shows that the secondary perfusion test method can quantitatively study the interface healing of asphalt,and the healing of asphalt interface is affected by the holding time.The effect of the holding temperature is very large,and the degree of healing is very low under low temperature and short-term healing conditions.Polyphosphoric acid and slaked lime did not exert the expected effects under the conditions defined in this test.?2?The dynamic shear rheometer was used to the MSCR?Muti-Stress Creep and Recovery?mode.The special test ring was used to make the 70#matrix asphalt into a double-piece group with internal defects?3mm+3mm?and once.The molded monolithic?6mm?specimens were studied for the damage h ealing of asphalt samples under different test temperatures,parallel plate spacing,healing time and healing temperature,and the DSR temperature scanning test results were compared.The analysis found that the ratio of the creep recovery ratio?S_R?and the irreversible creep compliance ratio of the MSCR test at the test temperature of 25°C and the parallel plate spacing of 5 mm after healing at 40?for 2 min(S_Jnr))can be used as an evaluation index of self-healing properties of asphalt binders.?3?In this paper,the MSCR test was used to evaluate the damage healing performance of aged asphalt.Studies have shown that as the degree of aging deepens,the healing ability of 70#matrix asphalt and SBS modified asphalt gradually decreases.Among them,TFOT short-term aging has a greater impact on SBS modified asphalt than 70#matrix asphalt.With the continuous addition of new asphalt,the recovery rate R of the blended asphalt is gradually reduced,the unrecoverable creep compliance J_nrr is gradually increasing,and the healing performance is gradually increased.It is worth noting that the complex modulus of the blended pitch with 50%to 75%new asphalt does not change much.