Research On Mechanical Properties Of Asphalt Mixture With Interlayer Interface Under Water And Salt Erosion

At present,more and more asphalt pavements are approaching the design service life,and various diseases are gradually emerging,such as subsidence,rutting,wrapping and moving.When these diseases cause functional damage to the asphalt pavement and can not meet the normal driving demand,the commonly used maintenance method can directly pave a new layer of asphalt concrete on the old asphalt pavement,so as to extend the service life of the pavement.This method has the advantages of small traffic impact,short construction period and good pavement service performance after repair.However,the overlay asphalt concrete will be affected by the residual disease of the old asphalt pavement and the erosion of environmental factors.The anti fatigue performance and anti shear performance of asphalt mixture with interlayer interface will be affected after overlay.In order to study the performance of overlay materials of old asphalt pavement which have experienced different diseases and cold weather conditions,this paper,aiming at the problems of AC-16 old asphalt pavement diseases caused by water immersion and salt erosion,considers the overlay of SMA-13 new asphalt pavement,and then undergoes water freeze-thaw and salt freeze-thaw environment conditions,carries out the overlay with interlayer interface by combining macro and micro test methods Three point bending fatigue test and shear strength test of pavement materials.The main research results and conclusions are as follows: compared with the new pavement,the fatigue life of the double-layer trabeculae of the old pavement with water immersion in the lower layer is reduced,and the fatigue life of the double-layer trabeculae of the old pavement with salt erosion in the lower layer is reduced more obviously.Salt erosion is one of the most important factors affecting the fatigue life of trabeculae.Compared with the double-layer trabecular without freeze-thaw cycle,the fatigue life of the double-layer trabecular after water freeze-thaw is reduced,and the fatigue life of the double-layer trabecular after salt freeze-thaw is reduced more.Salt freeze-thaw is one of the most important factors affecting the fatigue life of trabeculae.With the increase of freeze-thaw cycles,the fatigue life of double-layer trabeculae decreases.Freeze thaw 12 times has the greatest influence on the fatigue life of double-layer trabeculae.The results show that the shear strength of oblique shear specimen can be improved obviously by using oil.Compared with the new pavement,the interlaminar shear capacity of the old pavement with water immersion in the lower layer decreases,and the interlaminar shear capacity of the old pavement with salt erosion in the lower layer decreases more seriously.Salt erosion has the greatest influence on shear resistance.The interlaminar shear strength of oblique shear specimens after water freezing and thawing is lower than that of oblique shear specimens without freezing and thawing cycle,and the interlaminar shear strength of oblique shear specimens after salt freezing and thawing is more serious.Salt freeze-thaw has the greatest influence on shear resistance.With the increase of freeze-thaw cycles,the interlaminar shear strength of oblique shear specimens presents a downward trend.The results show that freeze-thaw for 12 times has the greatest influence on the shear resistance of oblique shear specimens.By using digital speckle technique,the micro observation of three-point bending fatigue test and oblique shear failure test of double-layer trabeculae under different conditions shows that the average horizontal strain of double-layer trabeculae increases suddenly in the failure stage of path 1 and 2;the existence of interlayer interface makes the lower layer always in tensile state,and path 2 shows greater horizontal strain.The interlaminar cracks begin to appear in the diagonal shear specimens before and after loading to 150 s,and develop rapidly.The interlaminar cracks begin to appear in the lower layer after salt erosion earlier than the specimens soaked in water and without treatment,and the interlaminar cracks become longer with the increase of freeze-thaw cycles.