| It is one of the causes of asphalt pavement damage and disease caused by external load,especially the damage caused by reflection crack.In winter,pavement cracking caused by low temperature and deicing salt seriously affects the service quality and service life of asphalt pavement.The temperature stress accumulation and strain are greater than the limit stress and strain of asphalt mixture;salt invades the interface between asphalt and aggregate,reduces the cohesive force and causes asphalt to fall off from the aggregate surface.It is easy to cause asphalt pavement cracking under load.Therefore,it is very important to improve the durability of asphalt pavement and slow down the occurrence and propagation of cracks.Therefore,the low temperature performance and salt corrosion performance of pre cracked asphalt mixture are studied from the perspective of material and environment.Coal gangue powder(CGP)is selected as asphalt filler,and the replacement rate is 0%,25%,50%,75%and 100%.The toughening material polyester fiber(PF)is selected as the reinforcing material and added into the asphalt mixture with the content of 0.0%,0.3%,0.4%and 0.5%of the total mass.Low temperature bending test is to conduct three-point bending test under the environmental conditions of 10℃,0℃,-10℃ and-20 ℃.Salt erosion is performed in water,NaCl saturated solution,Na2SO4 saturated solution,and CH3COONa saturated solution for 7 days and then subjected to high temperature accelerated corrosion for 24 hours,then cooled to room temperature and then subjected to a three-point bending test.A pre crack is set in the center of the specimen to simulate the influence of reflection crack on the low temperature crack resistance and salt corrosion performance of asphalt mixture.The depth of pre cracking is 10 mm and the with is 1.5 mm.The influence of material and environment on low temperature performance and salt corrosion performance of pre cracked asphalt mixture is studied.Through bending test,scanning electron microscope test(SEM)and X-ray diffraction test(XRD),the main conclusions are as follows.(1)Temperature has certain influence on the anti-cracking performance of coal gangue powder-polyester fiber(CGW-PF)asphalt mixture.At 10℃ and 0℃,the mixture is ductile failure;at-10℃,there are both ductile failure and brittle failure;at-20℃,the critical temperature of brittle failure is 0℃～-10℃.(2)The results show that the tensile strength of the mixture is 574.0%when the amount of polyester fiber is 764.0%and the tensile strength of the mixture is 574.0%when the content of polyester fiber is 764.0%.It shows that the replacement rate of coal gangue powder should be 50%,and the content of polyester fiber should be between 0.3%and 0.4%.(3)With the decrease of test temperature,the flexural tensile strength and flexural stiffness modulus of coal gangue powder polyester fiber asphalt mixture change in accordance with the law,but the failure strain is opposite to the change law.(4)When the replacement rate of coal gangue powder(CGP)is 50%,the coal gangue powder(CGP)has smaller particle size and larger specific surface area than the mineral powder.When the coal gangue powder(CGP)and mineral powder are half mixed into the mixture,the filler can be further refined to make the asphalt mixture more-dense and enhance the ability to resist external load.When the content of polyester fiber is 0.4%,the internal part of the mixture is more evenly dispersed,which can play the role of reinforcement and bridge,and delay the appearance and expansion of cracks in asphalt mixture.(5)Coal gangue powder-polyester fiber(CGP-PF)can improve the salt corrosion and bending resistance of asphalt mixture.In saturated sodium chloride solution,the content of polyester fiber(PF)should be 0.4%,and the substitution rate of coal gangue powder(CGP)should be 50%.In the saturated sodium sulfate solution,the polyester fiber(PF)content is 0.4%,and the substitution rate of coal gangue powder(CGP)is 75%.In the saturated sodium acetate solution,the polyester fiber(PF)content is 0.3%～0.4%,and the replacement rate of coal gangue powder(CGP)is 50%～75%.(6)Different salt solutions have different erosion mechanisms for coal gangue powder-polyester fiber(CGP-PF)asphalt mixture.The adsorption capacity of Na+and Cl-ions in saturated sodium chloride solution to the aggregate is stronger than that of asphalt,and it has a certain stripping effect on the asphalt on the surface of the aggregate.The surface tension of saturated sodium sulfate solution is much higher than that of asphalt at normal temperature or even high temperature.Compared with asphalt,it can fight for more aggregate surface,and sulfate crystals hinder the self-healing ability of asphalt mixture.Saturated sodium acetate solution causes the loss of polar components in the asphalt to reduce the adhesion between asphalt and aggregate.(7)When the content of polyester fiber(PF)is 0.4%and the replacement rate of coal gangue powder-polyester fiber(CGP-PF)asphalt mixture is 50%,the maximum value of stress intensity factor is 54.6882 MPa·mm0.5,48.1423 MPa·mm0.5,39.6311 MPa · mm0.5,46.8152 MPa·mm0.5,respectively.Compared with the asphalt mixture without polyester fiber,the SIF of coal gangue powder asphalt mixture increased by 58.84%,48.07%,40.05%and 47.52%,respectively.(8)The corrosion ability of salt solution to gangue powder polyester fiber asphalt mixture is in the order of Na2SO4 saturated solution,NaCl saturated solution and CH3COONa saturated solution.Figure[39]table[27]reference[61]... |
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