| Fiber asphalt mixture is one of the important innovative materials for constructing long-life and durable pavement with better performance.The reinforcement effect of fiber on asphalt mixture is significant.However,the synergistic mechanism of fiber type and characteristic parameters with asphalt mixture needs to be more precise,which becomes the bottleneck problem in the application and development of fiber asphalt mixture.In this paper,the synergistic effect and mechanism of fiber types,characteristic parameters and matrix were studied from two levels of fiber-asphalt mortar and fiber-asphalt mixture.The main research work and conclusions are as follows:Study on the synergistic effect of fiber and asphalt mortar.The properties of fiber asphalt mortar at different temperatures were tested.The synergistic effects between fiber and asphalt mortar with different types and characteristic parameters were studied using a performance model and two-way ANOVA.The experimental results show that fibers can improve the high-temperature performance and fatigue life of asphalt mortar and significantly increases the fracture property and tensile stress of asphalt mortar but reduces the elongation and creep rate of asphalt mortar.It can be seen from the performance law of the fiber asphalt mortar when the fiber type and length are the same,the smaller the fiber diameter,the better the performance of the asphalt mortar.When the fiber type and diameter are the same,the performance of asphalt mortar increases first and then decreases with the increase in fiber length.The results of modeling and two-way ANOVA show that the weight of fiber length and diameter on the properties of asphalt mortar is ranked as 6 mm>3 mm>12 mm,7μm>16 μm>25 μm,respectively.Study on the synergistic mechanism of fiber and asphalt mortar.The synergistic mechanism between fiber types,characteristic parameters and asphalt mortar was studied by analyzing the bond strength,structural asphalt properties and interface properties of fiber asphalt mortar.The results show that the strength of the asphalt mortar was improved because the fiber increased the viscosity of the asphalt mortar and significantly enhanced the proportion and strength of structural asphalt.Compared with glass fiber and polyester fiber,the effect of basalt fiber on the performance of asphalt gel is optimal and the influence of fiber characteristics is more prominent.The results of the monofilament fiber pull-out test show that fiber type and specific surface area are the key factors affecting the interfacial properties of fiber asphalt mortar.The results of the critical embedded length of monofilament fiber show that the smaller the difference from the critical embedded length of the fiber,the more beneficial it is to improve the reinforcement effect of fiber on asphalt mortar.The 6 mm long fiber has the advantage of improving the property of asphalt mortar.Study on the synergistic effect of fiber and asphalt mixture.The mechanical properties of fiber asphalt mixture at high temperature,medium temperature and low temperature were analyzed,and the synergistic effect between fiber and asphalt mixture was studied by performance model.The results show that the high-temperature stability,fatigue performance and low-temperature crack resistance of asphalt mixture were improved with the addition of fibers.Consistent with the law of fiber asphalt mortar,when the fiber type and diameter were the same,the performance of the asphalt mixture first increased and then decreased with the increase of fiber length.When the fiber type and length were the same,the performance of the asphalt mixture decreased with the increase in fiber diameter.The analysis of the performance model of fiber-modified asphalt mixture shows that the influence of fiber on the performance of asphalt mixture first depends on the characteristic parameters such as fiber length and diameter.Secondly,it is related to fiber elongation,surface properties and distribution.Study on the synergistic mechanism of fiber and asphalt mixture.The dynamic modulus,phase Angle and principal curve of fiber-modified asphalt mixture under various temperature conditions,crack cracking behavior based on Digital Image Correlation(DIC)and equal cross-section theory were used to study the synergistic mechanism between fiber and asphalt mixture with different types and characteristic parameters.The effects of fiber types and characteristic parameters on the properties of the asphalt mixture are consistent with those of asphalt mortar,and the fibers of different types and characteristic parameters have a significant effect on the elastic and viscous components in the asphalt mixture at different temperatures.At high temperatures,when the specific surface area and the number of fibers are relatively large,it is beneficial to realize the adsorption of asphalt and limit the flow of asphalt.In this case,the storage modulus of the asphalt mixture increases and the loss modulus decreases,significantly improving the high-temperature deformation resistance of the asphalt mixture.At low temperatures,fiber is beneficial in reducing the energy accumulation in the asphalt mixture and increasing internal friction.At this time,the storage and loss modulus was reduced,significantly improving the crack resistance and toughness of the asphalt mixture.According to the results of the DIC analysis,adding fibers increased the initiation energy of the asphalt mixture and the energy loss during cracking.The crack growth rate of the loading energy was also increased,and the crack propagation direction was changed,significantly delaying the crack cracking.The results of the equal cross-section theory showed that when the fiber length was the same,the larger Young’s modulus of the fiber and the smaller the fiber diameter would improve the performance of the asphalt mixture.Through the analysis of the synergistic effect of fiber-modified asphalt mortar and fiber-modified asphalt mixture,the optimum selection criteria of fiber based on the performance of AC-13 asphalt mixture are proposed as follows:First,the fiber modulus priority criterion;Second,the minimum fiber diameter criterion;Third,the optimum length of 6 mm;Fourthly,the preference criterion of specific surface area and monofilament number.Following the selection criterion of fiber is beneficial to improve the synergistic effect of fiber with asphalt mortar and asphalt mixture.It provides a theoretical reference for applying a high-performance fiber-modified asphalt mixture. |
