Research On Influence Of The Blending Status Between Virgin And Aged Binders On Pavement Performance Of Recycled Asphalt Mixture With High RAP Content

The blending status between virgin and aged binders is not always completely miscible in the hot-recycled asphalt mixture with high content of Reclaimed Asphalt Pavement(RAP).Therefore,the design method of recycled asphalt mixture based on the complete miscibility of the blending status between virgin and aged binders proposed cannot be applied to the high RAP content of recycled asphalt mixture,which limits the efficiency use of RAP materials.Therefore,quantifying the blending status between virgin and aged binders and establishing its relationship with pavement performance are the key issues in perfecting the design method of pavement performance of recycled asphalt mixture with high RAP content.Three kinds of high content RAP materials(30%,40%,50%)of AC-16 hot-recycled asphalt mixture were chosen for this study.By changing the mixing temperature(150°C,165°C,and 180°C)and using the method of complete extraction and mixing,four mixtures with different miscibility levels were gotten.Based on modified Hirsch model,theoretical prediction of the master curves of dynamic modulus of the mixtures with different miscibility levels was reached and compared with the measured values.The experimenter quantitatively characterizes the blending status between virgin and aged binders,tests each pavement performance(high temperature stability,low temperature property,water stability,fatigue performance),and analyzes the relationship between changes in miscibility and pavement performance of the mixture.The influence of the pavement performance with the blending status between virgin and aged binders of the recycled mixture was determined.Through this research,it was found that when the RAP content was 30%,40%,and 50%,the miscibility of the blending status between virgin and aged binders in the mix was 85.5% to 95%,80.5% to 87.5%,and 74.5% to 80.5% at different mixing temperatures,respectively,and all of them were less than 100% miscible.Therefore,it is impossible to adopt a standardized method for the design of high-RAP hot-recycled asphalt mixture.And as the RAP content increases,the blending status between virgin and aged binders shows a downward trend.Increasing the mixing temperature can significantly improve the blending status between virgin and aged binders.The dynamic stability of the recycled mixture under three kinds of RAP dosages in different miscibility meets the specification requirements,but the dynamic stability decreases significantly with the blending status between virgin and aged binders.At the time of design,this study suggests adopting the method in this paper,which is that the blending status between virgin and aged binders is completely miscible to prepare the mixed material sample,and then check whether the high temperature stability is the normative standard.The water stability and low temperature property of the recycled mixture with three kinds of RAP content increased continuously with the increasing of the blending status between virgin and aged binders.The rudimental stability and low-temperature tensional strain of the mixture at the 50% RAP content did not meet the specification.It is required that the water stability and low temperature property of the mix increase with decreasing RAP content.Therefore,the water stability and low temperature property of the mix at high RAP content are properties that need to be focused on.While increasing the blending status between virgin and aged binders,the water stability and low temperature property of the mixture can be significantly improve.For fatigue performance,at three different strain levels(200με,400με,600με),the fatigue life of the reclaimed mixture increases with the increasing the blending status between virgin and aged binders,but it decreases with the increase of RAP content.The degree of miscibility can significantly improve the fatigue performance of the mix.Finally,based on this research,this study introduces the blending status between virgin and aged binders based on the current regeneration specifications,and it also proposes a design process for hot-recycled asphalt mixture of high RAP content,which will provide the theoretical basis to perfect design method for hot-recycled asphalt mixture.