| SBS modified asphalt is widely used in the upper layer of road asphalt because of its advantages of high temperature resistance,low temperature resistance and rutting resistance.However,the high construction temperature of SBS modified asphalt mixture is easy to lead to asphalt aging,energy consumption,pollutant emission and other problems.In order to reduce the construction temperature of SBS modified asphalt,warm mixing technology is adopted.Among them,wax is commonly used as the organic viscosity reducing agent in the warm mixing technology,and waste plastics can be obtained by catalytic cracking organic viscosity reducing wax warm mixing agent,which not only realizes waste utilization,but also reduces pollution and saves energy.Therefore,in this paper,homemade warm mixture waste plastic cracking wax(PEW-1)and industrial production waste plastic cracking wax(PEW-2)were added into SBS modified asphalt to study their effects on the properties of SBS modified asphalt and mixture.The main research contents and corresponding conclusions are as follows:1.The kinetic experiment shows that the amount of catalyst is 0.8% of the mass of waste plastics,the reaction temperature is 270℃,and the reaction time is 30 min.Under this reaction condition,the waste plastics cracking wax with viscoaverage molecular weight between 2000-2500 and good performance can be obtained.2.The basic performance test of asphalt shows that compared with the pure SBS modified asphalt,the injection degree of the warm mixed modified asphalt at 25℃decreased by 33.39% and 37.39%,respectively,after mixing 6% PEW-1 and PEW-2.The elongation at 5℃ decreased by 56.34% and 65.86%,respectively,and the low temperature performance decreased.The softening point increased from 74℃ to 83.5℃and 78.9℃ respectively,and the high temperature stability was enhanced.After aging,the quality loss rate is reduced and the anti-aging property is improved.The temperature scanning test showed that the critical temperature of asphalt increased from 76.35℃ to92.62℃ and 85.75℃,respectively,after adding 6% PEW-1 and PEW-2,and the high temperature performance was enhanced.The mean recovery percentage(R%)of asphalt at 0.1k Pa pressure increased from 95.54% to 98.97% and 95.92%,and the mean non-recoverable creep compliance(Jnr)decreased from 0.48 to 0.07 and 0.11,respectively,when 6% Peu-1 and Peu-2 warm mix was added.The results indicated that the addition of warm mixing agent enhanced the rutting resistance and permanent degeneration resistance of asphalt at high temperature.3.Combined with the Brinell viscosity and contact Angle tests,it was found that both the two warm mix agents could effectively reduce the viscosity and adhesion properties of SBS modified asphalt.The results of Brinell viscosity test showed that mixing temperature of 5%PEW-1 and 6%PEW-2 was reduced by 19℃ and 20℃,respectively.Combining the viscosity reduction effect and performance characteristics,PEW-1 mixing 5%,PEW-2 mixing 6% is the best.4.Through microscope observation,it is found that PEW-1 microscopically presents a granular "honeycomb" shape with a relatively stable structure;PEW-2 showed a "tree" shape with large voids and relatively low structural stability,but the distribution of warm mix agent in asphalt was good.Fourier infrared spectrum found that the characteristic peak did not change,the mixture of warm mix agent and asphalt is just a simple physical action,and no chemical reaction.5.Design the mix ratio through Excel planning and solving,and determine the optimal amount of asphalt is 6%.By fitting the voidity-compaction temperature curve with the linear equation to calculate the inverse compaction temperature,the highest temperature drop of SBS modified asphalt mixture at 6%PEW-1 temperature is 28℃,and the highest temperature drop of SBS modified asphalt mixture at 5%PEW-2 temperature is 27℃.6.The rut test results show that compared with the pure SBS modified asphalt,the dynamic stability of SBS modified asphalt mixed with 5%PEW-1 and 6%PEW-2 increases by 65% and 57.6%,respectively,and the high temperature performance is improved.The tensile strength ratio of freeze-thaw splitting was increased to 91% and 92%,the residual stability was increased to 89% and 91%,and the water stability was enhanced.However,the maximum flexural tensile strain is reduced by 20.1% and 22.4% respectively,and the low temperature property is reduced,but it meets the specification requirements. |
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