| Road maintenance process,the use of asphalt overlay can improve the road performance of the old asphalt pavement,with the use of time,the old pavement on the joints,cracks at the horizontal displacement will continue to expand,but because of the bond between the overlay layer and the old pavement,so that the horizontal displacement of the overlay layer is blocked and the tensile stress in the overlay layer,when the tensile stress exceeds the tensile strength of the mixture,the overlay layer will appear reflection cracks.Reflective cracks as the main damage form of the cover layer,will greatly reduce its service life and increase the cost of road maintenance.Due to the advantages of high tensile modulus,high strength,high temperature resistance and corrosion resistance,glass fiber grating is widely used in asphalt overlay to mitigate or inhibit reflective cracking.At present,there are many indoor tests for evaluating reflection cracks at home and abroad,but there are two problems: first,the geometry of the specimens is large,the operability is poor,and the dispersion of the fatigue test results is large;second,the use of monotonic loading cannot simulate the real traffic conditions and the evaluation index is single.It is important to use this test method to reasonably select glass fiber grating,to reveal the reflection crack expansion process of glass fiber grating cover layer,to evaluate the performance of glass fiber grating against reflection cracks by using a new index-"damage rate",the role of glass fiber grating in the process of reflection crack expansion and the mechanism of crack expansion.This paper firstly uses Superpave rotating compressionIn this paper,the volume parameters of the mix were first measured by the Superpave rotary compaction method,and the design porosity volume parameters were calculated using 4% porosity as the control index to obtain the optimum amount of asphalt required for the test.Subsequently,the indirect tensile strength,indirect tensile rebound modulus,and indirect tensile creep tests of the asphalt mixture were conducted using UTM-30,and the final strength,rebound modulus,creep flexibility,m,and D1 values of the asphalt mixture were measured to prepare for the subsequent theoretical study and experimental analysis.Based on the indoor test to evaluate the large geometry of anti-reflection cracking specimens,poor operability,and difficulty of specimen preparation,Superpave rotary compaction molding composite shaped specimens with the maximum directional geometry of 150 mm were used.secondly,theThe bending test and fatigue test of composite shaped small beam specimens were conducted to study the effect of different sizes of glass fiber grating with the same cross-sectional area on the resistance to reflection cracks.The results showed that the denser the grating mesh was when the cross-sectional area of glass fiber grating was the same,the higher the span deflection,ultimate damage load,bending stiffness modulus and fatigue number were,and several sizes of grating were higher than the control specimens(without grating).In addition,a new evaluation index,"damage rate",is proposed to characterize the cumulative rate of damage of composite specimens during the fatigue test,which is used to evaluate the effect of glass fiber grating against reflection cracks,and the smaller the damage rate,the better the performance of glass fiber grating against reflection cracks.Finally,the CSIC(Composite Specimen Interface Cracking)specimen was developed to reduce the dispersion of fatigue test results,which can effectively reduce the dispersion of fatigue test results and provide support for evaluating the performance of the grating against reflection cracks and theoretical research.In order to understand the role of glass fiber grating and the fracture sequence of grating and cover layer in the reflection crack expansion process,this study uses HMA fracture mechanics to analyze the crack expansion process with the following assumptions: firstly,the damage of the material is caused by the dissipation energy accumulated in the material;secondly,the crack expansion is a stepwise process;through computational analysis,the asphalt cover layer is damaged before the grating,followed by The relationship between the number of load cycles and crack extension length was established,and the whole process of reflection crack extension was elaborated.Finally,ABAQUS finite element software was used to simulate and verify the results of indoor tests and HMA fracture mechanics calculations.The relationship between the number of load cycles and the crack extension length is established and compared with the HMA calculation results,and the error is within the controllable range.Therefore,when the model parameters,mesh division and boundary conditions are selected reasonably,the FEM can predict the anti-reflection crack performance reliably. |
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