Pre-treatment Of Crumb Rubber And Properties Of Activated Crumb Rubber Modified Asphalt

Waste crumb rubber modified asphalt has the advantages of excellent high temperature stability and low noise.At the same time,waste crumb rubber is obtained by recycling waste tires,which has the advantages of low price and environmental friendliness.Therefore,waste crumb rubber modified asphalt has good application prospects.However,due to insufficient compatibility between waste crumb rubber and asphalt,segregation is easy to occur,resulting in poor stability of modified asphalt.In addition,the viscosity of the waste crumb rubber modified asphalt is larger,and the higher temperature is required during the preparation and paving process,which is detrimental to the road performance of the modified asphalt mixture.This paper aims at the defects such as high viscosity,poor storage stability and insufficient low temperature performance of waste crumb rubber modified asphalt,carries out pre-activation of waste crumb rubber and its modified asphalt performance research to provide a reference for the practical application of the project.In this paper,one waste crumb rubber is selected,three activation schemes are designed,and pre-activated waste crumb rubber with different parameters is prepared;The pre-activated waste crumb rubber was characterized by scanning electron microscope,infrared spectroscopy scanning test,thermogravimetric test,cross-link density test and dynamic thermomechanical test.It was found that microwave radiation contributed to the breakage of C = S bond,the molecular main chain and cross-linking bonds inside rubber molecules,and the swelling of diesel fuel has a positive effect on the reduction of the C = C bond content and the glass transition temperature;Rubber modified asphalt was prepared using pre-activated waste crumb rubber.Through the penetration,softening point,ductility and Brinell viscosity tests,the influence of pretreatment schemes on the engineering characteristics of rubber asphalt was studied.It was found that all three activation treatment schemes can reduce rubber asphalt penetration and viscosity,and diesel pre-swelling can reduce the sensitivity of rubber asphalt to microwave strength.A dynamic shear rheometer was used to characterize the high-temperature rheological characteristics,middle-temperature fatigue characteristics and low-temperature rheological characteristics of rubber modified asphalt through temperature scanning,amplitude scanning and frequency scanning,respectively.It was found that when the microwave intensity is 0.9k J/g?1.2k J/g,the high-temperature rheological properties and middle-temperature fatigue properties of rubber modified asphalt are improved,and the compound activation has the most obvious improvement effect on the rheological properties of rubber modified asphalt;Using gray correlation analysis to characterize the relationship between the rheological properties of rubber modified asphalt and the technical indicators of activated waste crumb rubber,the study found that the content of C=S is a key factor that affects the high-temperature and lowtemperature rheological properties of modified asphalt.The content of C=C has a greater influence on the fatigue performance of modified asphalt at moderate temperature.Using the segregation value of the softening point to evaluate the thermal storage stability of rubber modified asphalt,it was found that microwave radiation helps to reduce the segregation value,and the stability of the composite activated waste crumb rubber modified asphalt is better than that of single microwave radiation.Based on the failure temperature to evaluate the aging resistance of rubber asphalt,composite activation will damage the aging resistance of modified asphalt.Comprehensive evaluation of rubber asphalt various characteristics was performed by ranking equal weights,and found that compound activation was the optimal activation method,10% was the optimal diesel fuel dosage,and 1.2k J/g was the optimal microwave radiation intensity.Fluorescence microscope test was used to observe the distribution of rubber particles in modified asphalt,the change of molecular weight in modified asphalt was characterized by gel chromatography test,and then separate the rubber particles from modified asphalt,observe the surface shape by electron microscope appearance.The interaction between rubber and asphalt was revealed,and it was found that diesel pre-swelling helped to supplement the light components in the modified asphalt,microwave radiation helped to crack the rubber macromolecules,and composite activation helped to modify the uniformity of the asphalt increased stability.Selecting SMA as the gradation type,composite activated waste crumb rubber modified asphalt mixtures with different parameters were prepared,and the road performance of the mixture was characterized by rutting test,Marshall water immersion stability test and low temperature bending test.The result shows that the composite activation improved the low-temperature crack resistance of the modified asphalt mixture and enhanced its ability to resist water damage,but the composite activation had little effect on the high-temperature deformation resistance.