Experimental Study On Performance Of Sand-mist Seal On Asphalt Pavement With Self-healing Function

With the increase of mileage and service years of high-grade highways in China,many asphalt pavements have been damaged early after they were built and opened to traffic,and pavement maintenance becomes more and more important.Therefore,the study of a fast,convenient and cost-effective technology to alleviate the early diseases of asphalt pavement has become one of the key technical problems of highway construction and maintenance in China at this stage.Fog seal is an important preventive maintenance measure,but the traditional fog seal has some problems,such as insufficient skid resistance and wear resistance,easy cracking and poor durability,which hinder the development of preventive maintenance technology.Therefore,this paper developed a self-healing sand-mist seal,which has good shape memory and self-healing ability,can adapt to the temperature field changes of asphalt pavement working environment and can be self-repaired in time when the mist seal cracks to prolong the service life of asphalt pavement when the fog seal cracks.At the same time,it does not affect the skid resistance and wear resistance of asphalt pavement,which is of great significance to promote the development of preventive maintenance technology of asphalt pavement.Firstly,SBS polymer modifier and multi-walled carbon nanotubes(MWCNTs)were selected to prepare SBS/MWCNTs composite modified emulsified asphalt.The shape memory properties of composite modified emulsified asphalt were studied by shape memory test.The microstructures of samples were analyzed by fluorescence microscopy,Raman spectroscopy,X-ray diffraction and environmental scanning electron microscopy.The interaction mechanism of phase components in samples was studied,and the shape memory mechanism of samples was revealed.It was found that the composite modification of SBS/MWCNTs gave the shape memory properties of the samples,and the incorporation of MWCNT significantly enhanced the shape memory properties.The optimum contents of SBS and MWCNTs were respectively determined to be 4%and 0.03%.Secondly,in order to enhance the self-healing performance of composite modified emulsified asphalt,basalt(BS)fibers,polyethylene terephthalate(PET)fibers and polypropylene terephthalate(PTT)fibers were selected to modify the composite modified emulsified asphalt,and fiber reinforced composite modified emulsified asphalt was prepared.The conventional properties,bonding properties and high and low temperature properties of the samples were characterized to determine whether the fiber modified emulsified asphalt meets the requirements of the current technical specifications.The results show that the penetration,softening point and viscosity of the samples are improved to some extent by the three kinds of fibers,but the ductility index is reduced,and the low temperature crack resistance and high temperature deformation resistance of the samples are also improved.In a word,the PTT fibers with 0.35%content have the most obvious effect on the improvement of the basic properties of the composite modified emulsified asphalt.Thirdly,in order to study the effect of the three kinds of fibers on the self-healing properties of composite modified emulsified asphalt,the self-healing tests of damaged specimens were carried out under different conditions.The results show that both PET and PTT fibers improve the self-healing properties of specimens,while BS fibers reduce the self-healing properties of specimens.In addition,the index HI~3,which defines the self-healing property by the ratio of dissipated energy before and after self-healing,is the most representative.It was determined that0.35%PTT fibers have the best effect on improving the self-healing performance of the sample.It was also confirmed that the shape memory property of the fibers can promote the self-healing of the composite modified emulsified asphalt in multiple cycles.Finally,two kinds of fine grained sand,quartz sand and machine-made sand,were selected to prepare sand-mist seal.The road performance of sand-mist sealing was studied through waterproof performance,anti-skid performance and anti-wear performance tests.The results show that the sand-mist seal has good self-healing,water sealing and wear resistance,which can improve the appearance of asphalt pavement and the skid resistance of asphalt pavement.Comparing comprehensively,the road performance of sand-mist seal made of manufactured sand is better.In a word,the self-healing sand-mist seal developed in this paper overcomes the problems of insufficient skid resistance,poor wear resistance and short service life of conventional mist seal,which is of great significance to promote the better and faster development of preventive maintenance technology of asphalt pavement,and to improve the durability and service quality of asphalt pavement.