| As our country’s asphalt pavement is facing ever-increasing material performance requirements to meet the rapid increase in traffic volume and axle load,and climate change,in response to the current social urgent need to reduce traffic noise,combined with the increasingly prominent environmental pollution caused by insufficient recycling and utilization of waste tires,the research was based on the limitation of rubber content and the mutual restriction of road performance and road function.It was guided by improving the noise reduction function of the rubber asphalt mixture,and the core goal was to increase the rubber content.The key technology of rubber asphalt mixture with high content is formed by systematically studying the reaction mechanism of rubber asphalt and the noise reduction mechanism of the mixture,the preparation process of high-content rubber asphalt mixture,the design method of dry-wet composite high-content rubber asphalt mixture,the road performance and noise reduction function of high-content rubber asphalt mixture.It lays a foundation for the practical application of asphalt pavement with low noise,high performance,environmental protection and economy.Combining the microscopic test and solubility test,the reaction mechanism of rubber asphalt was clarified.The main reaction mechanism of rubber asphalt is swelling and degradation.The swelling reaction can significantly enhance the high temperature performance and elasticity of rubber asphalt,while the degradation reaction can lead to the decline of the high temperature performance and the increase of viscosity of rubber asphalt.The properties of rubber asphalt are closely related to the reaction stage.For different reaction temperatures(170～230℃)and stirring rates,the rubber powder would absorb the light oil in the asphalt and swell,but only when the temperature is up to 190℃,the fully swollen rubber powder would begin to degrade,so temperature is the key parameter affecting the rubber asphalt reaction.Combining the reaction mechanism of rubber asphalt and the noise reduction mechanism of tire-pavement noise,it pointed out and improved the shortcomings of the noise reduction mechanism of rubber asphalt mixture in the traditional view,and then clarified the target focus of dry and wet rubber asphalt technology.The wet method should focus on asphalt modification,and the dry method should focus on noise reduction.Taking complex modulus,phase angle and elastic recovery as the evaluation index of rubber asphalt noise reduction function,using the three major indexes as the evaluation index of rubber asphalt road performance,and using viscosity as the control index of rubber asphalt construction and workability to test and compare the performance and functional performance of rubber asphalt under different rubber powder content(15～35%),different reaction temperature(170～230℃)and different reaction time(8～225min).With the solubility of rubber asphalt as a guide,the analysis of the change law and internal mechanism of rubber asphalt properties with the powder rubber powder and reaction conditions were used to guide the adjustment and optimization of rubber asphalt preparation conditions.Finally,the preparation process of high content rubber asphalt was determined: the content of rubber powder was 35%,the content of aromatic oil was 7.5%,the reaction temperature was 230℃,the reaction time was 225 min,and the stirring rate was 800r/min.On the basis of fully ensuring the construction and workability of the rubber asphalt,the road performance and noise reduction function of the rubber asphalt were effectively improved.Adhere to the principle of giving full play to the advantages of high-volume and large-size rubber particles in noise reduction,and ensuring that the mixture has reliable road performance.Combining the material characteristics of high-volume and large-size rubber particles,the improved main skeleton void filling method was adopted.The gradation design of the rubber asphalt mixture with dense skeleton structure,the discontinuity of the fine aggregate provides the filling space for the rubber particles.Considering that it is difficult to mix rubber particles and mineral materials uniformly,and the swelling reaction will occur in contact with asphalt under high temperature conditions,the mixing process was improved,the mixing time is increased,and the "high temperature stuffing" link was added to fully ensure the volume stability and mechanical properties of the rubber asphalt mixture.When the content of rubber particle does not exceed 2.5%,the measured volume parameters of the mixture were close to the design values,and the clearance ratio of the skeleton was less than the clearance ratio under the coarse aggregate tamped state,indicating that the design method is suitable for high-content rubber asphalt mixtures.Taking into account the important influence of the open pore connectivity state in the road surface texture on the air pump mechanism,based on the structural depth index,an effective structural depth index was proposed as an evaluation index for the texture noise reduction of the mixture,combined with the mixing complex modulus and phase angle of the evaluation index for vibration and noise reduction of materials can more accurately and effectively reflect the noise reduction level of the mixture.The test results showed that the rubber asphalt mixture with 2.5% rubber particles is superior to AC and SMA in high temperature stability,low temperature crack resistance and vibration noise reduction.The water stability was slightly worse,and the texture noise reduction ability was close to that of SMA,much higher than AC.When removing aggregates with a particle size of 13.2mm in the rubber asphalt mixture,the low temperature crack resistance,water stability,vibration noise reduction and texture noise reduction capabilities showed significant improvement,although the high-temperature stability has declined,but it had also maintained a high level,which was close to the SMA mixture. |
