Study On Crack Propagation Of Basalt Fiber Asphalt Mixture

The pavement of high grade highway in China is mainly asphalt pavement.Due to the effect of seasonal temperature difference and load in Inner Mongolia Autonomous regio,the micro-cracks formed in the asphalt pavement will continue to expand and develop into macroscopic cracks,eventually leading to the destruction of the pavement structure.Basalt is a main material of basalt fiber,and it is rich in reserves in China.Basalt fiber can not only avoid the deficiency of traditional fiber for asphalt mixture,but also can improve its road performance,avoid early damage of asphalt pavement,and has considerable economic benefits.Therefore,basalt fiber plays an important role in the cracking and propagation of cracks in asphalt pavements.The paper has carried out the following research work:?1?The research object of this paper is AC-16 asphalt mixture.The bonding materials are ordinary matrix asphalt and matrix asphalt with basalt fiber.The amount of asphalt used for the two types of mixture,the ratio of oil and stone,and the amount of aggregate used for the corresponding mortar are determined,and made specimens.It is concluded that the bitumen aggregate ratio of the two mixtures is 4.9%and 5.1%,respectively.The bitumen aggregate ratio to the two kinds of mortar is 8.6%and 8.9%respectively.The results show that basalt fibers can infiltrate and adsorb bitumen in the mixture and increase the amount of asphalt and thus increase the ratio of oil to stone of mixture and mortar.?2?The surface information of AC-16 asphalt mixture semi-circular specimen is collected by digital camera,then Image-ProPlus-6 and R2V software are used to perform some operations on the image,and setting up aggregate and cohesive units in CAD.Finally,the.Sat is introduced into the finite element calculation software ABAQUS to form a two-dimensional semicircular specimen model.?3?In this paper,the viscoelastic properties of ordinary asphalt mortar and asphalt mortar mixed with basalt fiber are analyzed by Burgers model.The linear elastic model is used for aggregate and CZM model is used for contact section between aggregate and mortar.In finite element ABAQUS simulation,the definition of viscoelasticity of asphalt mortar requires the curve between creep compliance and time obtained from uniaxial static compression creep test.The elastic modulus E_1?E₂ and viscosity coefficients?₁ and?₂ in Burgers model were obtained by Origin fitting,and then the four parameters were transformed into Prony series.Through the load-displacement curve obtained by the semi-circular bending test,it can be concluded that the vertical deformation of the mortar with asphalt mixture mixed with basalt fiber is significantly bigger than that of the matrix asphalt mixture during the loading stage and under the same load.It shows that the incorporation of basalt fiber can coordinate the deformation of asphalt mixture.The cohesion force?CZM?model was defined by the critical cohesion and critical fracture energy parameters obtained by the SCB test.The results showed that the two fracture parameters were obviously increased by the incorporation of basalt fibers.The stress cloud diagrams of semi-circular bending specimens of two materials were obtained through numerical simulation of semi-circular bending test.The comparative analysis showed that basalt fiber can effectively disperse and transmit stress in asphalt mixture.The stress intensity factors at the crack tip of the two materials were compared by empirical formulas and finite element simulations to verify the accuracy of the input of the material parameters in the finite element simulation.Under the same load,the stress intensity factor of the crack tip of the asphalt mixture mixed with basalt fiber is smaller than that of the base asphalt mixture,indicating that the basalt fiber can effectively distribute the stress distribution at the crack tip.It can well relieve the cracking of cracks;?4?In this paper,scanning electron microscopy?SEM?was used to observe the microstructure of asphalt mixture and basalt fiber mixed asphalt mixture,and the effect of basalt fiber on cracking in asphalt mixture was analyzed qualitatively.First,the effect of basalt fiber on the interface between asphalt and asphalt was analyzed by observing the contact between basalt fiber and asphalt in the asphalt mixture;and then,by observing the fracture surface of two materials and the fracture of basalt fiber,it analysis the effect of basalt fiber on the reinforcement and crack resistance of asphalt mixture;finally,by observing the distribution of basalt fiber in the micro-cracks of mixture,it analysis the effect of basalt fiber on the microcrack growth of asphalt mixture.