A Study On Mix Design Of Recycled Asphalt Concrete With High Reclaimed Asphalt Pavement Content

Hot Recycling is the most widely used renewable technology in road engineering. But the content of old material is usually low, so the regeneration economic efficiency and effectiveness of Hot Recycling are affected. This paper focuses on the variation of high temperature stability, low temperature crack resistance and water stability when old material content increases, the paper puts forward old material content definition and whetstone ratio prediction method considering volume indicators as controlled conditions.This paper confirmed the technical feasibility of a high dosage of old material recycled asphalt mixture, achieving the highest 50% of the old material content.The difference in geological conditions of the road, how long road was used, traffic volume and layers in which old material in and other factors may cause the variation of old gradation, moisture content and aggregate ratio. This paper makes a study on the relationship between the moisture of old material and the the layer in which the old material in. Focusing on the graded variation law the rearch divides the old material into three kinds as 9.5mm-19mm,2.36mm-4.75mm and≤2.36mm.Then we can get old material grading variation range from specific experimental data. So the recycled asphalt mixture he overall grading scale ranges of variation are:5%,6% and 3% for 40% RAP content. And recycled asphalt mix gradation range can not meet the specification requirements.Starting from the strength of recycled asphalt mixture composition principle, taking control of 4.75mm sieve rates to the limit to ensure the performance stability of recycled asphalt mixture, demonstrating the superiority of mix design method in low and water stable performance.Meanwhile this paper makes simulate experimental study on influence of RAP content on recycled asphalt mixture compaction effect. And optimizing the high dosage of old material recycled asphalt mixture mixing process consdering the distribution of bitumen membrane.This study reveals performance law of Hot Recycling asphalt mixture and old material variability comprehensively, providing mix design methods for asphalt mixture with high old material dosage, exploring asphalt metastasis when old and new material are mixed.It is a theoretical basis for the further study.