Research On Aging Self Healing Property And Mechanism Of Nano Montmorillonite Modified Asphalt

Highway construction in China is developing rapidly,The production and application of road asphalt is great significance for the development of national highway transportation construction.China has vast territory and huge difference in climate and environment,Therefore,asphalt materials placed in natural conditions should have good environmental adaptability.The Inner Mongolia Autonomous Region,located in the north of China,has the characteristics of high latitude,dry climate,intense ultraviolet radiation and high solar radiation,Therefore,the modified asphalt with good aging resistance is needed as a pavement material.In addition,It is found that asphalt has the phenomenon of self healing in practical application,This refers that performance of asphalt will be recovered spontaneously under natural conditions,This phenomenon is conducive to prolong the service life of asphalt pavement.Therefore,Research on aging resistance and self healing properties of modified asphalt is of great significance for service life and road effect of asphalt and asphalt pavement.In this paper,nano montmorillonite as asphalt modifier was blend with matrix asphalt and SBS modified asphalt to prepare MMT modified asphalt and SBS/MMT modified asphalt by high speed shear emulsifier.The microstructure of the modified asphalt before and after aging was observed by atomic force microscopy(AFM),Besides that,bending beam rheological test(BBR),three major indexes,cloth type viscosity test and ductility test(DTH)were used to measuring macroscopic properties,and researched effects of MMT on properties of high temperature,low temperature,resistance and self healing property of asphalt,It can provides reference basis for road application value of nano montmorillonite modified asphalt.BBR result show that low temperature performance of matrix asphalt and SBS modified asphalt decreased with addition of MMT modifier,but performance of SBS/MMT composite asphalt after long-term aging is stronger than SBS modified asphalt,which attributable to better aging resistance of SBS/MMT composite modified asphalt.In addition,the custom indicators,change rate of stiffness modulus S_V,evaluate aging resistance of nano montmorillonite modified asphalt with residual penetration ratio,softening point increment and residual ductility ratio,the results show that adding MMT modifier can significantly improve aging resistance of asphalt,S_V as evaluation index can better understand performance of aging asphalt in low temperature environment,which can better reflect aging resistance of asphalt,but low temperature performance of the asphalt should be fully considered.The result of asphalt rotating viscosity shows that MMT will improve high temperature performance of asphalt,the performance of MMT modified asphalt is obviously better than SBS modified asphalt with same content,MMT has same improvement to SBS modified asphalt,and MMT\SBS composite asphalt has best high temperature performance.The fitting results of viscosity temperature curve show that MMT can greatly improve viscosity and high temperature performance of asphalt,meanwhile,it also increase difficulty of construction owing to high mixing temperature,therefore,the content of MMT should be reduced properly on the premise of ensuring high temperature performance.The result of viscosity temperature index VTS show that temperature sensitivity of MMT modified asphalt and SBS modified asphalt is lower than matrix asphalt,MMT\SBS composite asphalt is the Worst,Aging will reduce temperature sensitivity of the four types of asphalt and the high temperature performance is enhanced.DTH result show that MMT as asphalt modifier will reduce self healing property of matrix asphalt and SBS modified asphalt,SBS modified asphalt has the best self healing property,the second is matrix bitumen,and MMT modified asphalt is the worst,in addition,MMT has significant inhibition effect on self-healing behavior of SBS modified asphalt.The self healing property of matrix asphalt are weakened after aging,while nano montmorillonite modified asphalt is improved,which means that it is more meaningful to research the healing performance of montmorillonite modified asphalt combined with aging effect.AFM result show that MMT has significant effect on microstructure of asphalt,the"bee structure"of AFM morphologies gradually disappears with the increase of MMT content,and forms the nano composite structure,while the structure and MMT layer are the main reason for delaying aging.Through phase diagram,it is found that the interface of two phases is gradually fused with the increase of MMT content,resulting in the decrease of micro cracks between two phases and the weakening of self healing property of asphalt.After the aging of the asphalt,the nanocomposite structure is destroyed.After aging,the nano composite structure is destroyed,with MMT layer falls off,the"bee structure"reappears and the boundary between two phases becomes obvious,the interface is reseparated,the micro cracks increase,and the self healing property of nano montmorillonite asphalt are enhanced.The results show that,MMT as asphalt modifier can formed the nano composite structure with asphalt,which significantly enhance the aging resistance and self healing property after aging of asphalt,but decrease low temperature performance.nano montmorillonite modified asphalt has wide development space and application prospect,It can work together with other modifiers to improve asphalt performance more comprehensively.