Research On Fatigue Damage Characteristics Of High RAP Hotmix Plant Recycling Asphalt Mixture Considering Creep Effect

With the progress of society and the development of the industry,a large amount of reclaimed asphalt pavement(RAP)is generated every year from the renovation of asphalt pavement.According to the requirements of resource conservation and environmental protection,the recycling of high RAP content has become an inevitable trend.In addition,the climatic environment of asphalt pavement complex and changeable,the viscoelasticity of the material is more prominent,and the simple fatigue damage theory can no longer meet the requirements of the research work on fatigue damage of asphalt pavement.In order to study the creep effect in the process of fatigue damage evolution of high RAP hot mix asphalt plant recycling asphalt mixtures,and to reveal the damage evolution law of high RAP hot mix plant recycling asphalt mixtures considering the creep effect,this paper carried out a based on creep-fatigue fatigue damage study of high RAP hot mix plant recycling asphalt mixtures based on coupled damage theory.70#petroleum asphalt and SBS modified asphalt were used to prepare high RAP hot mix plant recycling asphalt mixtures,and dynamic creep tests at different temperatures were carried out to determine the compliance shift factor of thermally recycled mixture at different temperatures.The calculation formula of loss compliance was deduced according to the efficiency principle;the rheological model based on the Burgers model and the Boltzmann superposition principle was used to fit and analyze the test results,and the viscoelastic parameters of the high content thermal regeneration mixture were obtained;Direct tensile fatigue tests at different temperatures and loading stress ratios were carried out to explore the effects of different test conditions(different temperatures and loading stress ratios)on key indicators such as stiffness modulus,critical damage degree and fatigue life during the mixture fatigue test.The fatigue damage evolution law of the high RAP hot mix plant recycling asphalt mixtures was revealed,and the fatigue damage model and life prediction model of the high RAP hot mix plant rccycling asphalt mixtures considering the creep effect were obtained.The test results show that:when 70#petroleum asphalt and SBS modified asphalt are used for regeneration,the optimal new asphalt oil stone ratios are 2.2%and 2.3%,respectively;with the loading times,the rate of change of the deformation of the specimen during the creep test It showed a trend of fast at first,then slow and finally increased rapidly,and with the increase of temperature,the trend of steady growth was shorter;different test conditions(ie test temperature and loading stress ratio)had a The damage degree and the number of fatigue life will have a significant impact;for the initial modulus,the test temperature is the main influencing factor;while the residual modulus and critical damage degree are affected by the loading stress ratio and the test temperature at the same time;the creep effect considering the creep effect The variable-fatigue coupled damage model and fatigue life prediction model fit well with the test data,and according to the relationship between model parameters and temperature,a fatigue life prediction equation including temperature factors is established...