Study On The Temperature-dependent Characteristic Of PE/SiO₂ Composite Modified Asphalt

It is an important research direction of asphalt modification at present by adding different types of modifiers to base asphalt to improve the high and low temperature performance of asphalt and prolong the service life of asphalt pavement.What’s more,it is the key to prolong the service life of asphalt pavement on how to choose the type of modifier.At the same time,based on the concept of national construction of resource-saving,ecological and environment-friendly highways and sustainable development of highway construction,it is currently a research hotspot in the road industry to use plastic（PE）materials with huge daily consumption as modifiers to improve the asphalt pavement performance.However,due to the variety of plastics and the easy agglomeration of asphalt molecules,plastic modified asphalt is prone to segregation during thermal storage,which limits its large-scale popularization and application.At the same time,although plastic modifiers have improved the high-temperature performance of asphalt,the evaluation of its low-temperature performance is still controversial.Therefore,in order to select suitable plastic modifiers,improve the high temperature performance of plastic modified asphalt and its storage stability,the evolution law of its low temperature performance was deeply excavated and analyzed.In this study,SiO₂,an inorganic nano-material with anti-aging property,was selected as an additive and different types of plastics were used to compound and modify the matrix asphalt.Based on storage stability test,rheological test,low temperature test,the storage stability and rheological properties of composite modified asphalt with different modifier types and different additive dosage were discussed.The best type of plastic modifier and the best content of SiO₂ additive were selected.The evolution law of its low-temperature performance was comprehensively evaluated,and the micro-composition and structure morphology tests of the composite modified asphalt were quantitatively analyzed.The change law of micro-composition and the change characteristics of structure morphology were quantitatively analyzed,and the relationship between its micro-composition,structure morphology performance and macro road performance was obtained.Studies have shown that:（1）The storage stability of three different PE plastics（LDPE,HDPE,and LLDPE）composite modified asphalt is related to the properties of the plastic modifier itself.Under the same SiO₂ content and different plastic types,LLDPE modifier has narrow molecular weight distribution,high melting point and good heat resistance,and its composite modified asphalt has small overall softening point difference and low segregation rate.The addition of SiO₂ makes the plastic modifiers in asphalt distribute evenly to a certain extent,forming a more dispersed spatial structure.However,due to the small particle size of SiO₂,the plastic particles would become denser when the content is more.Moreover,the lipophilic and hydrophobic physical characteristics of SiO₂ make it affect the light component content of matrix asphalt when it is added at 0.4%and 0.6%,and then affect the storage stability of plastic modified asphalt.（2）The high temperature properties of PE/SiO₂ composite modified asphalt,such as softening point and viscosity,are all factors that affect its storage stability.The order of factors affecting its storage stability is:SiO₂ content>softening point>PG classification>penetration>viscosity>phase angle at 70℃by Grey Relation Analysis.（3）Compared with single plastic modified asphalt,the ductility at low temperature increases with the increase of additives.Due to the divergent nature of SiO₂ additive itself,a network space structure is formed in the internal structure,and the force between SiO₂additive and asphalt molecules becomes larger.The macro performance is that compared with a single plastic modified asphalt,the ductility at low temperature is larger,and the cracking resistance is improved.（4）Based on Fourier transform infrared spectroscopy analysis,the changes in the content of main functional groups in the composite modified asphalt before and after aging were quantitatively characterized.The study found that the composite modified asphalt containing SiO₂ additive was less affected by aging.The research shows that the dispersion of LLDPE composite modified asphalt is better than that of LDPE and HDPE composite modified asphalt after using Matlab image processing technology to quantitatively characterize the micro-morphology of modified asphalt.（5）The analysis of micro-macro correlation degree shows that the macro creep rate has a greater correlation degree with the micro functional group index,and the segregation degree has the lowest correlation degree with the functional group index factor.The complex modulus at 70℃is highly correlated with the distribution index of modifier,and the distribution characteristics of modifier are highly correlated with the high temperature rheological properties of composite modified asphalt,and the indexes of composite modified asphalt with 0.2%SiO₂ additive are better than other blending ratios.