| Crack propagation has a serious impact on the performance of bridge deck pavement.When cracks propagate inside the pavement layer,they will cause serious damage to the integrity and stability of the pavement layer,resulting in a decrease in the bearing capacity of the pavement layer,damage and collapse of the bridge structure,uneven surface,and accelerated water infiltration,thereby accelerating the damage and aging of the pavement layer.Therefore,understanding the causes and mechanisms of crack propagation can predict and evaluate the propagation path and speed of cracks,so as to take effective prevention and repair measures as soon as possible.Crack propagation behavior has always been the frontier field of asphalt pavement theory and practice research.Especially in recent years,the increase in the number of surface cracks and the harm to asphalt pavement have caused the research of many scholars at home and abroad.In recent years,the bridge deck pavement materials used in China are mostly epoxy asphalt concrete.Although this material has high strength and stiffness and high durability,it has strict requirements on construction conditions,high material costs,and unstable performance under low temperature environmental conditions.Therefore,based on the pavement material,this thesis selects ARHM-13 and ARHM-20 rubber modified asphalt mixtures with high rubber powder content of 30 % and 40 %respectively,and carries out raw material index detection and mix ratio design.Based on this,the road performance is tested.The deformation,dynamic stability and splitting strength ratio are all composite specifications,and the high temperature stability and water damage resistance of ARHM-13 asphalt mixture are better.The crack resistance of ARHM-20 graded asphalt mixture is better than that of ARHM-13 graded asphalt mixture at low temperature.In order to further evaluate the crack resistance of the two gradation types of asphalt mixture,the fracture energy and fracture toughness were selected as the evaluation indexes.The standard trabecular specimens of the two materials were made respectively,and the pre-cutting treatment was carried out.Three-point bending tests at different temperatures and different crack lengths were carried out.The parameters such as fracture energy and fracture toughness are calculated by the data obtained from the test,and the temperature sensitivity analysis is carried out.The results show that the crack resistance of ARHM-20 asphalt mixture is better,and the fracture energy is better as the evaluation index of crack resistance of asphalt mixture.In order to study the propagation behavior of cracks in the presence of surface cracks and reflection cracks,this thesis made a composite slab specimen of asphalt bridge deck paving brick layer scale model,and carried out cracking test under different temperatures and different crack relative positions.The test results are analyzed from the perspectives of crack propagation deflection angle,crack propagation rate and crack propagation process.The results show that the propagation rate of reflective cracks is much larger than that of surface cracks.The reflective cracks expand in the direction of load application at the initial stage of upward propagation,and rapidly expand in the direction of surface cracks after passing through the bonding layer. |
