| Along with the promotion of CIR technology and the growth of CIR pavement use time,more and more CIR pavements are reaching their service life,and the remaining value of the CIR RAP is huge,so it is important to study its reuse in a forward-looking way.However,there is limited research at home and abroad on the repeated recycling technology of e CIR RAP,and a complete evaluation system,design method and performance control standard for the old material has not been formed yet.Therefore,the main purpose of this study is to clarify the secondary use of CIR RAP,as well as the control of key parameters of different recycling processes,and provide a complete and feasible secondary recycling method for CIR RAP as well as performance control standards.First,to ensure the consistency of the raw materials for secondary recycling tests and the comparability of the subsequent test results,CIRM was prepared indoors using RAP,and the CIR RAP and its material properties were obtained after indoor aging and manual kneading and separation.Secondly,the preparation process and key ratio parameters of CR-CIRM and HR-CIRM based on CIR RAP were investigated.On the one hand,with reference to the CIR design methods at home and abroad,the CR-CIRM design method was proposed from the mix perspective,comparing the changes of compaction characteristics with the increase of cold recycling times,establishing the correlation equation between the optimal moisture content and cement content,and determining the key parameters of the ratio design such as the optimal cement content and the optimal amount of regenerated asphalt through splitting tests;on the other hand,based on the correlation between asphalt mortar and asphalt mixture,the effect of different RAP admixture and oil-to-rock ratio on the rheological properties,fatigue properties and high temperature properties of recycled mortar was investigated through TTS,LAS and modified MSCR performance tests,and the design method of HR-CIRM based on the concept of performance balance was determined.Then,X-Ray CT industrial scanning imaging technology was used to compare CIRM and CR-CIRM,and the void distribution characteristics of the two mixtures were clarified;2D slice and scan image technology combined with Matlab image analysis technology was used to obtain the coarse aggregate contact characteristics and mortar thickness distribution characteristics of CR-CIRM and HR-CIRM.Finally,the road performance of CR-CIRM and HR-CIRM were compared and analyzed by using tests.Compared with CIRM,high temperature performance and cracking strength of CR-CIRM decay significantly,fatigue performance under high stress conditions is insufficient;compared with hot mix asphalt mixture and HIRM,HR-CIRM has better high temperature stability,cracking resistance,in order to meet the fatigue performance of the use requirements,the amount of RAP is recommended to be controlled within 70%.CR-CIRM has high cost of consumables,high compaction difficulty and significant performance decay,so it has low value of engineering practice when applied to highway medium surface layer.The performance of HR-CIRM with less than 50% of RAP is better and can be used in highway surface layer projects.The research results of this paper lay the foundation for the reuse of emulsified asphalt cold recycled RAP material in highway maintenance projects. |
