Study On The Effect Of Aging On Meso-cracking Characteristics Of Warm Mix Crumb Rubber Modified Asphalt Mortar

Crumb rubber modified asphalt mixture has been widely recognized at home and abroad due to its good road performance.Warm mixing technology can effectively reduce its construction temperature and reduce environmental pollution.The impact of road performance needs further study.Asphalt pavement is easy to crack in the low temperature season,and the aging effect will further reduce its crack resistance.The crack resistance of asphalt mortar is directly related to the crack resistance of the asphalt mixture,so it is of great significance to study the cracking characteristics of warm-mixed crumb rubber modified asphalt mortar.Digital image correlation method?DIC?is a non-contact,high-precision,full-field optical measurement method,which provides an effective method for studying the meso-cracking characteristics of asphalt mortar.This article uses SDYK surfactant type warm mix crumb rubber modified asphalt mortar?CRS-WAM?,EM viscosity reducing agent type warm mix crumb rubber modified asphalt mortar?CRE-WAM?,hot mix crumb rubber modified asphalt mortar?CR-HAM?)As the research object,based on the theory of damage mechanics,fracture mechanics and interface mechanics,using DIC technology to study the effects of thermal oxygen aging and ultraviolet aging on the mesocracking characteristics of CRS-WAM,CRE-WAM and CR-HAM.First,image acquisition of the single-sided notched bending beam?SENB?test using DIC,and the horizontal displacement?U?and horizontal strain?EXX?of the crack initiation point were calculated by VIC-3D software.Based on the EXX definition of the area damage factor D,analysis Effects of different aging conditions on the deformation and damage characteristics of the cracking point of asphalt mortar.The results show that no matter what kind of aging method,the damage resistance of asphalt mortar is reduced,the cracking time is advanced,and the D value accumulation speed becomes faster.Among the several aging conditions studied,simulated outdoor natural ultraviolet light aging for five years?UVA5?has the most severe impact on the cracking performance of asphalt mortar;the two types of warm-mixed crumb rubber modified asphalt mortar have better damage resistance and aging resistance than hot-mixed crumb rubber modified asphalt mortar,and CRS-WAM is the best,followed by CRE-WAM.Secondly,the load-displacement curve of the SENB test is used to calculate the flexural tensile strength?R_B?,the maximum flexural tensile strain??_B?,the flexural stiffness modulus?S_B?,and the fracture toughness J_ICand the stress intensity factor K are calculated.Influence of different aging methods on fracture characteristics of asphalt mortar.At the same time,the influencing factors of K were analyzed using ABAQUS peripheral line integrals.The results show that no matter what kind of aging method,the anti-fracture ability of asphalt mortar is reduced,and the effect of UVA5 conditions is the most serious.The two kinds of warm-mixed crumb rubber modified asphalt mortar have better anti-fracture and anti-aging ability than CR-HAM,and CRS-WAM is the best,followed by CRE-WAM;the value of K increases with the increase of crack length,the decrease of the tilt angle of the crack,and the decrease of the distance between the crack position and the mid-span,and the asphalt mortar becomes more and more easy to crack.Finally,the crack propagation rate of the asphalt mortar interface is calculated based on the aggregate-asphalt mortar interface length and the inclination angle.The EXX-defined interface damage factor D_Ibased on the DIC technique is used to analyze the influence of different aging methods on the asphalt mortar interface characteristics.The cohesive force model was used to establish a finite element model of the SENB test.Based on this model,the influencing factors of the crack propagation path at the interface were analyzed.The results show that no matter which aging method is used,the crack growth rate of asphalt mortar increases,D_Iincreases,the bonding strength of the aggregate-asphalt mortar bonding interface decreases,and the effect of UVA5 conditions is the most serious.Compared with CR-HAM,the crack propagation rate of slow asphalt mortar is slower,the interface bond strength decreases less,and the CRS-WAM performance is the most obvious,followed by CRE-WAM.The finite element model of the SENB test has higher reliability and interface adhesion.The smaller the adhesion and tilt angle,the larger the fracture energy,and the longer the interface,the easier the interface is to crack.