Research On Performance And Microscopic Properties Of Asphalt Mixture Modified By Nano TiO₂/CaCO₃ And Basalt Fiber

Asphalt concrete pavement has the advantages of comfortable driving,small noise and so on,which has been widely used in the field of road engineering.However,there will be various diseases of asphalt concrete pavement with the service period increasing.Many factors may cause diseases on asphalt pavement,such as vehicle load,environmental temperature and rain scour.The performance of asphalt mixture is one of the main internal causes.Therefore,people try to reduce or avoid the occurrence of disease by improving the performance of asphalt mixture.Asphalt modification is commonly used to improve the performance of asphalt mixture.The modification of asphalt can be divided into three kinds: process modification,structural modification and modifier modification.At present,the modification of modifier has aroused great interest of researchers.The research show that the modification of nanomaterials and basalt fibers has a certain effect on improving the performance of asphalt mixture in some aspects.Nanomaterials mainly improve the high temperature and water stability of asphalt mixture,while basalt fiber mainly improves the low temperature performance of asphalt mixture.With the aim of simultaneously improving the high and low temperature performances and water stability of asphalt mixtures,this paper combines the National Nature Fund Project “Study on the damage model and mesoscopic characteristics of freeze-thaw cycles of asphalt concrete in seasonally frozen areas” and the technology project of the Jilin Provincial Transportation Department “Study on damage characteristics and mechanism of basalt fiber asphalt concrete under the coupling of water and temperature”.The performance and mesoscopic characteristics of nanomaterials and basalt compound modified asphalt mixture were studied.The specific research work is as follows:(1)Based on cone penetration test,Brookfield rotational viscosity test,softening point test,dynamic shear rheology(DSR)test,ductility test and beam bending rheology(BBR)test results,the shear resistance,viscosity characteristics,high temperature stability,high temperature rheological properties,low temperature ductility,and low temperature rheological properties of nanomaterials and basalt compound modified asphalt was evaluated.The composite modification mechanism of basalt fiber and nanomaterials to asphalt was revealed by scanning electron microscopy(SEM).(2)Basalt fiber content,nanomaterial content and asphalt-aggregate ratio were used as response input indicators,and density,stability,flow value,asphalt saturation,and mineral material gap ratio were used as response output indicators.Response surface method was adopted to optimize the design process of nanomaterials and basalt compound modified asphalt mixture,and the optimal values of asphalt-aggregate ratio,basalt fiber content and nanomaterial content were determined.Based on this,the road performance test of asphalt mixture was performed,and the influence of variation of basalt fiber and nanomaterial contents on the performance of various asphalt pavements was analyzed.(3)The base asphalt mixture,the nanomaterials modified asphalt mixture,the basalt fiber modified asphalt mixture,and the nanomaterials and basalt fiber modified asphalt mixture were prepared using the best asphalt-aggregate ratio,and then subjected to freeze-thaw cycle test.The decay and damage mechanisms of various mechanical properties after freeze-thaw cycles of these asphalt mixtures were studied to evaluate the effect of nanomaterials and basalt fiber on the mechanical properties of modified asphalt mixture after freezing and thawing cycles.(4)The mesoscopic characteristics of base asphalt mixture,the nanomaterials modified asphalt mixture,the basalt fiber modified asphalt mixture,and the nanomaterials and basalt fiber modified asphalt mixture were extracted using digital image processing technology and the effect of the mesoscopic characteristics was analyzed.The mesoscopic characteristics of these four asphalt mixtures after freeze-thaw cycles were compared and analyzed,and the intrinsic relationship between mesoscopic characteristics and freeze-thaw resistance was revealed.(5)The base asphalt mixture,the nanomaterials modified asphalt mixture,the basalt fiber modified asphalt mixture,and the nanomaterials and basalt fiber modified asphalt mixture were prepared using rotary compaction method and Marshall compaction method,respectively.The Marshall stability test,the splitting strength test,the dynamic indirect tensile test,and the uniaxial static and dynamic load compression creep tests were used to compare and analyze the effects of two molding methods on the freeze-thaw resistance of these asphalt mixtures.Based on digital image processing technology,the influence of two molding methods on the mesoscopic characteristics of these asphalt mixture was discussed through parameters such as void number and void morphology.