Performance Study On Warm Mix Recycled Asphalt Mastic Containing High Percentage Of RAP Binder

Warm mix recycled asphalt(WMRA)technology is developed from warm mix asphalt(WMA)technology and hot mix recycled asphalt(HMRA)technology,which takes full advantage of these two technologies.This technology can significantly reduce the construction temperature and increase the percentage of reclaimed asphalt pavement(RAP)with good economic and environmental benefits.However,some studies indicated that the addition of high percentage of RAP and WMA additives had an adverse effect on the low-temperature cracking resistance,fatigue resistance and moisture susceptibility of WMRA mixture,and thus how to improve the road performance of asphalt mixture has become the research focus of WMRA technology.Current studies mostly focus on the performance of WMRA binder and mixture,and limited work has been performed to study the asphalt mastic containing both WMA additives and RAP binder.Asphalt mastic is considered as an important part of asphalt mixture and directly affects the road performance,which provides a new research direction for the design optimization of WMRA mixture with high RAP content.To this end,this dissertation investigated the performance of warm mix recycled asphalt mastic containing high percentage of RAP binder and the following research efforts were made:(1)Two types of WMA additives with different modification mechanisms(R and M)were selected for the preparation of WMRA mastic,which were consisted of synthetic wax and surfactant respectively.The filler/asphalt ratio(F/A)ranged from 0.0 to 1.5 and the recycled asphalt binder was blended with 50% artificial RAP binder.The Superpave performance grade test was carried out to study the high-temperature,fatigue and low-temperature performance of WMRA mastic containing high percentage of RAP binder.The combined effect of RAP binder and WMA additives on the performance of asphalt mastic was assessed and the relationship between F/A and the Superpave performance grade test indicators was quantified.(2)On the basis of the Superpave performance grade test results,a series of rheological tests were conducted to evaluate the temperature sensitivity,high-temperature creep and recovery property,viscoelastic property and fatigue performance of WMRA mastic with high proportion of RAP binder.The research results indicated that RAP binder,WMA additives and mineral fillers led to various temperature sensitivity of asphalt mastic,and their effects on the high-temperature creep and recovery property were similar to the Superpave high-temperature performance grade test results.Also,the addition of RAP binder and mineral fillers could increase the dynamic shear modulus and lower the phase angle at the same time,but the effect of WMA additive M on the viscoelastic property was very limited.However,asphalt mastic exhibited complicated viscoelastic property due to the polyethylene and wax components within WMA additive R.Further,the recycled RAP binder and WMA additive M could improve the fatigue potential under stress-controlled and strain-controlled load modes,while WMA additive R and mineral fillers exhibited the opposite effects on the fatigue performance of asphalt mastic under different load mode.(3)Interface behavior and microscopic properties play a critical role in determining the macroscopic performance of WMRA mastic.The interfacial property of asphalt mastic within the linear viscoelastic range was evaluated through interface parameter Luis Ibrarra-A,and the interface behavior under damage conditions was further analyzed.The chemical functional groups and thermal property of WMRA mastic were measured by FTIR and DSC to explore the modification mechanisms of RAP binder and WMA additives.(4)Based on the dynamic shear modulus master curves,Superpave performance grade test results and rheological property parameters,the F/A difference between WMRA mastic containing 50% RAP binder and 90# asphalt mastic when they exhibited similar performance was determined.The F/A of recycled asphalt mastic with WMA additive M could decrease by 0.2~0.3 while recycled asphalt mastic with WMA additive R could keep the same F/A as 90# asphalt mastic,providing the theory basis for the design optimization of WMRA mixture containing high proportion of RAP.