| In order to alleviate the environmental problems caused by the accumulation of RAP materials and the increase in the price of asphalt and stone caused by the increasing road maintenance,the ultra-high proportion of plant mix hot recycling technology has always been widely valued.However,on the one hand,the variability of RAP materials from more diverse sources has a great impact on the road performance of recycled materials.On the other hand,insufficient fusion of new and old asphalt and low quality of the blended new asphalt result in poor performance of recycled asphalt,both of which restrict Utilization of ultra-high proportion thermal regeneration technology.Aiming at the above problems,this paper focuses on the variability of multi-source RAP and the variability of the road performance of recycled asphalt materials caused by the variability of RAP materials,the macro performance and micro mechanism of high rubber blending and recycled old asphalt,and the reliability theory is used to analyze the high RAP The mixing ratio of the mixed asphalt mixture is designed to ensure that the variability of the high RAP recycled asphalt mixture is controlled while the road performance is greatly improved.First,use combustion method,extraction method,sieving method,and three major index tests to evaluate the performance of RAP materials,and analyze the variability of multi-source RAP materials based on the coefficient of variation.The results show that the three indexes of old asphalt in RAP material have changed greatly,the whole is hard and brittle,and the aging is serious;taking 4.75 mm as the boundary,the aggregate of RAP material shows obvious agglomeration and refinement.In the same batch of RAP materials collected on the same road section,the gradation of the old materials,the content of the old asphalt,and the properties of the old asphalt are the main sources of variation in the composition of the RAP materials.The coefficient of variation of the pass rate of the aggregate 4.75 mm sieve is 13%～15% The variability is large,and the coefficient of variation of the old asphalt content fluctuates between 3% and 5%,and the variability is small.Scendly,taking recycled asphalt mixture as the research object,the influence of multi-source RAP material gradation variability on the road performance variability of recycled asphalt mixture is analyzed.The revised fineness modulus formula is used as the index to evaluate the gradation,and recycled asphalt mixtures with different fineness moduli are designed,and the rutting test,indirect tensile fatigue test,and low-temperature SCB test are used to evaluate the high temperature and fatigue of the recycled asphalt mixture,Anti-cracking performance.The results show that as the fineness modulus increases,the mixture gradation becomes coarser,the dynamic stability improves,and the high-temperature rutting resistance improves;the fatigue life under 0.25 stress ratio increases,and the fatigue performance improves;the fracture energy increases,and the low-temperature crack resistance performance Promote.Thirdly,use the coefficient of variation as the calculation index to calculate the ratio of the content,properties,and gradation fluctuations of the old asphalt of the RAP material to the road performance of the recycled asphalt mortar and mixture.From this ratio,it can be concluded that the impact on the high temperature performance of the recycled material is: RAP material gradation variability>old asphalt content variability>old asphalt property variability;in terms of the influence on the mid-temperature fatigue crack resistance of recycled materials,old asphalt property variability>old asphalt content variability>RAP material gradation variability;In terms of the impact on the low-temperature resistance to thermal shrinkage and cracking of recycled materials,the variability of old asphalt content>the variability of old asphalt properties>the gradation variability of RAP material.Fourth,take the high-rubber reclaimed asphalt mixed with different content of high-rubber asphalt and aged asphalt with different aging degrees as the research object,use the DSR-based macromechanical test of asphalt and the microscopic observation test based on AFM to evaluate the high-rubber asphalt Reconcile the regeneration effect for research.The results show that high-rubber asphalt can greatly improve the high-temperature deformation resistance and high-temperature elastic recovery of recycled asphalt,and the fatigue performance will also be greatly enhanced,but it will have a certain negative effect on the crack resistance performance of the G-R constant as the evaluation index.From the microscopic observation results and adhesion curve of the high rubber recycled asphalt,it can be concluded that the swelling effect of the rubber powder improves the high temperature performance and fatigue performance of the recycled asphalt,but the absorbed light components and wax content inhibit the "bee structure".Structure" is created,which also reduces the adhesion of reclaimed asphalt.Finally,relying on the reliability theory,the design method of recycled asphalt binder and the control method of RAP performance variability are established,and the design scheme of high RAP content hot recycled asphalt mixture is proposed based on the above design method.The results show that the variability of recycled materials can be controlled by screening RAP materials through the 4.75 mm sieve,and the road performance variability of recycled asphalt mixtures can still be maintained at 37.5%under the condition of 70% RAP content;high gum asphalt repair The reliability of aging asphalt pavement and returning to better performance reaches 81%.The high RAP content hot regenerated asphalt mixture prepared by using high gum asphalt as the blending asphalt and the process of binning the RAP material can achieve high temperature stability far exceeding the new material with lower variability without using regenerants. |
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