| Fiber is an effective means to improve the high and low temperature performance and crack resistance of asphalt mixture.Adding fiber into asphalt mixture can increase the life of asphalt pavement and improve the durability of asphalt pavement.But at present,there are many kinds of road fiber and the optimal fiber content is different,and the strengthening mechanism and fracture behavior of fiber asphalt mixture are unclear,which becomes the bottleneck problem that hinders the efficient application and development of fiber asphalt mixture.In this paper,the properties and fracture behavior of asphalt mixture with different fiber types and dosage were studied.Firstly,three kinds of basalt fiber,glass fiber,polyester fiber and five kinds of content of 0.1%,0.2%,0.3%,0.4%,0.5%were selected.The properties of fiber and other raw materials were tested,and the mix ratio of AC-13 asphalt mixture was designed by Marshall test.The results show that with the increase of fiber content,the optimum oil stone ratio of asphalt mixture increases.Secondly,the road performance of the fiber asphalt mixture was tested by rut test,low temperature trabecular bending test,immersion Marshall test and freeze-thaw splitting test.The results show that the fiber can significantly improve the high and low temperature properties of asphalt mixture,and with the increase of dosage,the improvement effect shows a trend of first enhancement and then decrease,and the basalt fiber has the best enhancement effect.In addition,the effect of fiber on the water stability of asphalt mixture is small.Then,the shear resistance of the fiber asphalt mixture was tested by uniaxial penetration test.The indirect tensile cracking test was used to analyze the cracking resistance by the parameters of initiation energy,fracture energy and CTindex.The dynamic modulus test was used to obtain the shift factor by fitting the WLF equation,and the Sigmoidal model was used to establish the principal curve of the dynamic modulus to evaluate the dynamic viscoelastic characteristics.The results show that the fiber can improve the mechanical properties of asphalt mixture,basalt fiber,glass fiber,polyester fiber asphalt mixture at 0.4%,0.3%,0.3%respectively,the improvement effect is the best,and basalt fiber is better.Finally,the strain field and real-time tensile strain during the cracking process of the fiber asphalt mixture were extracted synchronously by the digital image speckle technology,and the fracture parameters and crack tortuous coefficient were taken as indexes to quantitatively analyze the fracture behavior of the fiber asphalt mixture.The results show that the strain can be divided into two stages:slow growth and fast expansion.The fiber can play the role of crack resistance in the asphalt mixture,and the basalt fiber asphalt mixture has the best crack resistance in the two stages.The glass fiber is better than the polyester fiber in the first stage and worse than the polyester fiber in the second stage.In this paper,the effects of different types and mixtures of fibers on the pavement performance and mechanical properties of asphalt mixture were studied,and the fracture behavior was further studied based on digital image speckle technology.The results can provide beneficial reference for the use of fibers in asphalt pavement. |
