Issue 45

C. Huang et alii, Frattura ed Integrità Strutturale, 45 (2018) 108-120; DOI: 10.3221/IGF-ESIS.45.09 113 ratio is 0.17% ， .0.35% ， 0.52% and 0.69%, respectively. According to JTJ E20-2011 [13], the optimum asphalt content (OAC) of matrix asphalt mixture, fiber aspect fraction and volume fraction of asphalt mixes were determined. Rolling molding the test specimen of 300mm  300mm  50mm, and then were cut into a 250mm  30mm  35mm beam specimen. 15  C creep tests were performed by using a multifunctional material testing machine. The creep load is 10% of the beam bending failure load in the same condition, as shown in Fig. 5. Span deflection for the creep test of small beams is collected by using a dial gauge connected to the data acquisition system. Then the span deflection-time curve and the flexural tensile strain–time curves were drawn. When the beam specimens enter into the stage of accelerated creep stage then unload, and the test data were continued collecting for 30min. Based on the results of the creep test and assumed initial values of the model parameters in Eqn. (9) and (10), the nonlinear method of Origin 8.5 is used to obtained a best fitting between the theoretical results of the mechanical model and those from tests. The fitting effect is controlled by adjusting the model parameters. If the results match well, the viscoelastic parameters of the mechanical model can be achieved. Figure 5 : Creep test. R HEOLOGICAL TIME heological time from Eqn. (13) and the rheological time corresponding to the creep stability based on the measured creep deformation–time curves are listed in Tab. 1. It can be seen that the present model can calculate the rheological time efficiently and accurately, and the relative error is less than 10% between the values calculated by the present model and results from the tests. The rheological time is the start time of the destruction of AC under creep loads [1], the larger the value is, the longer the time taken to deform the test piece is and the stronger the ability to resist deformation of AC is. The test results show that, when the fiber volume fraction is 0.35% and the aspect ratio is 324, the rheological time of FRAC is the largest and FRAC has the best resistance to deformation. The variation of creep strain–time curves is shown in Fig. 6. It can be observed that when fiber volume fraction is 0.35% and the aspect ratio of fiber is 324, its curve is lower than others, and it means that FRAC has the best resistance to deformation at this moment. It is in accordance with the resistance to deformation from the present model based on the rheological time. Tab. 1 also shows the results of Burgers model and modified Burgers model. In comparison, the data from the present model is the closest to that of the stage of creep load among the three models, and the data of Burgers model has the largest deviation from the test data. The fitting curves of FRAC creep stain–time by using Origin8.5 software is shown in Fig. 7. It can be seen that the fitting curve of the Burgers model during the stage of deceleration creep is below the test curve, and model characterization of FRAC creep deformation is less than the actual deformation. In the stage of stable creep model, the model curve is above the experimental curve, and the creep deformation of model characterization is greater than that of the actual deformation. In the stage of accelerating creep, the deformation of model characterization is less than the actual deformation of AC and model curve is below the experimental curve. It should be noticed that the difference between the test curve and the model curve will be more significant until specimen fracture. The fitting curve from the modified Burgers and that from Burgers are somewhat alike in relation to the test curve, while the difference is R