| Due to the comfort brought by asphalt pavement,its proportion in China’s roads is increasing.However,due to the dual effects of environmental factors and external loads on the asphalt pavement during use,the asphalt pavement performance is degraded year by year until it is difficult to meet the road performance requirements.Asphalt pavement thermal regeneration technology not only shows certain advantages in improving resource utilization efficiency,reducing energy waste,and protecting environmental pollution,but also brings the greatest economic and social benefits to the society.Therefore,it is more and more widely used in the maintenance and construction of highway asphalt pavement.At present,due to the instability of the road performance of the hot reclaimed asphalt mixture,especially the fatigue performance of the reclaimed asphalt mixture with high dosage(more than 30%)is difficult to guarantee.Therefore,the thermal regeneration technology of asphalt pavement has not been widely promoted and applied.To this end,this paper starts from the high temperature stability,water stability and low temperature crack resistance of five kinds of RAP-doped hot reclaimed asphalt mixtures,especially the durability test research,mainly to carry out the following research work:(1)the content and age of RAP in RAP grading and RAP were analyzed by extraction and screening.In order to reduce the variability of RAP old materials,the RAP old material was divided into two grades with 9.5mm particle size.The gray correlation analysis was used to determine the blending ratio of the two RAP old materials in the recycled asphalt mixture.On this basis,the RAP content in the high-mixed plant mixed heat recycled asphalt mixture was determined.(2)Marshall test method is used to study the mix design of high-RAP mixed plant mixed heat recycled asphalt mixture.The optimum ratio of 0%,30%,40%,50%,60% of the recycled asphalt mixture of the 5 kinds of RAP content was determined to be 4.0%,4.3%,4.5%,4.7%,5.0%,respectively.The effect of RAP content on the optimum oil-stone ratio of recycled asphalt mixture and the amount of new asphalt was analyzed.The results show that the RAP content increases the oil-stone ratio of the recycled mixture and reduces the amount of new asphalt.(3)through the indoor test,the road performance and durability of the high-RAP mixed plant mixed heat recycled asphalt mixture were analyzed and studied,The single logarithmic regression fitting of the fatigue failure life of reclaimed asphalt mixture with high RAP content was used to characterize the influence of RAP content(30%、40%、50%、60%),stress ratio(0.3~0.6),loading frequency(2Hz、5Hz、10Hz)and test temperature(5℃、15℃、25℃)on the fatigue life of recycled asphalt mixture.Studies have shown that the RAP content,stress ratio and test temperature have a significant impact on the fatigue performance of high-recycled mixed heat mixed asphalt mixture.The increase of RAP content,stress ratio and test temperature will reduce the fatigue life of recycled asphalt mixture,and the increase of loading frequency will increase the fatigue life of recycled asphalt mixture.(4)By comparing and analyzing the fatigue prediction model of different asphalt mixtures,the relationship between fatigue life Nf and stress ratio C under the influence of different RAP content R,loading frequency H and test temperature T was fitted.The life Nf is approximately logarithmic to the stress ratio C,Based on the relationship between the parameters a,b and R,T and H of the fatigue equation,the fatigue prediction model of reclaimed asphalt mixture with parameters R,C,H and T is established,and the prediction effect of the indoor fatigue prediction model is carried out.The evaluation is intended to provide reference and guidance for the application of hot reclaimed asphalt mixture in engineering. |
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