Study Of Performance And Mechanism Of Fiber Reinforced Asphalt Mixtures

(Transportation College, Southeast University Jiangshu Nanjing 210096, China) Serious distresses in asphalt pavement, including rutting and cracks, are becoming common while freight vehicle traffic and axle loads are increasing quickly. This makes it a primary duty for researchers in highway engineering to develop performance enhanced asphalt mixtures. A fiber reinforced asphalt mixture may significantly improve pavement performance based on successful experiences with new types of reinforced fiber applied in cement concrete used in light structures. However, most research is currently focused on the performance of asphalt mixtures and so far there is no specific technical requirement regarding the addition of fiber in asphalt mixtures. This makes it imperative to study the performance and reinforcement mechanism of fiber reinforced asphalt mixtures. This dissertation not only elucidates the reinforced effect mechanism of fiber in asphalt mixtures, but also proposes a detailed method for selecting the concentration and length of fibers that should be added to asphalt mixtures. It is outlined as follows:â‘ Visco-elastic characteristic of asphalt materialsAt certain temperatures asphalt is a typical visco-elastic material and its mechanical actions are related to temperature, loading rate and time. Burgers'model is proposed to express the constitutive relationship of asphalt to effectively account for the time-temperature equivalence of the material. Based on visco-elastic theory, mechanical models under different loading conditions were set up. By BBR and DTT tests it was proved that Burgers'model can represent visco-elastic action of asphalt and reveal the damage process to the material along with loading history. Therefore, it can be used to predict the fatigue and rutting of asphalt mixtures.â‘¡Evaluation of fiber characteristics and fiber requirementsFiber is an additive to improve the performance of asphalt mixtures, but the reinforced effects largely depend on the fiber's characteristics. Therefore, the fiber's characteristics should be assessed for appropriate fiber selection. The interface strength between fiber and asphalt or asphalt mastic was measured to determine the critical concentration and critical length of added fiber. Moreover, the author analyzed the major properties of fiber and how it affects asphalt mixtures' performance, including dispersion, heat-durability and moisture absorption. Also technical requirements related to the addition of fiber into asphalt mixtures are proposed based on experiments on performance of fiber, fiber asphalt and fiber reinforced asphalt.â‘¢Performance assessment of fiber asphaltThe performance of fiber reinforced asphalt mastics relies on the mechanical characteristics of fiber (referred to as polymer fiber in this paper) and the properties of asphalt. With four methods (forced-ductility, DTT, BBR and DSR) the performance with different fiber content and fiber length was evaluated, and then the mechanism of fiber asphalt was discussed.â‘£Performance assessment of asphalt mixtures reinforced with fiberThe addition of fiber into asphalt mixture improves the performance of the material. The effect of different lengths, concentrations, and properties of fiber was assessed by experiments on performance of asphalt mixture such as rutting, resistance to cracking, fatigue and moisture...