Study On Modification Technology And Mechanism Of Waste Tire Rubber Powder Asphalt

The increasing number of waste rubber tires has attracted attentions of more and more researchers.Rubber asphalt has better performance compared with orginal asphalt.However,the compatibility between rubber powder and asphalt is poor because of the difference of physical and chemical properties and the improvement of high temperature performance of asphalt by rubber powder is very limited.In this work,rubber asphalt was prepared by tetraethyl orthosilicate（TEOS）modified rubber powder to improve the compatibility and high temperature performance of rubber asphalt.Due to the diversity of rubber asphalt preparation technology,the performance change of rubber asphalt was stydies.Taking the dosage of rubber powder,preparation temperature and fineness of rubber powder as independent variables,the physical properties of rubber asphalt as evaluation indexes.The influence of different factors on the performance of rubber asphalt was analyzed by variance analysis.The rubber asphalt has the best performance when the dosage of rubber powder is 20%,preparation temperature is 180^oC±5^oC,the fineness of rubber powder is 45 mesh,the shear time is60min and it was placed in 163^oC oven to develop 30min.The dosage of TEOS was taken as the independent variable and the effect of the independent variable on the performance of rubber asphalt was studied.The results show that physical properties of rubber asphalt are obviously increased when the dosage of TEOS is less.The rheological and fatigue properties of rubber asphalt with different TEOS dosage were tested and analyzed.The Brookfield viscosity of rubber asphalt increases with the increase of TEOS dosage.The complex shear modulus（G*）and phase angle（δ）of rubber asphalt increase first and then decrease with the increase of TEOS dosage.Rubber asphalt has the maximum G*and the minimumδwhen the dosage of TEOS is 25%.It is indicated that high temperature performance of rubber asphalt is the best.Compared with G*andδbefore and after aging of rubber asphalt,it is found that TEOS has no effect on the thermal oxygen aging resistance.In addition,it can be seen from the test results of linear amplitude scanning test（LAS）and multi stress creep recovery test（MSCR）of rubber asphalt that TEOS can significantly improve the resistance of rubber asphalt to external forces and improve the fatigue performance of rubber asphalt,but rheological performance of rubber asphalt is damaged when the dosage of TEOS exceeds 25%.Grey correlation analysis was used to determine the influence degree of different independent variables on the performance of rubber asphalt.It was found that the increase of TEOS dosage reduced the change of rubber asphalt performance according to the calculation results.TEOS can significantly improve physical properties,rheological properties and high temperature performance of rubber asphalt,and the reasonable dosage is determined as 20%-25%of the quality of rubber powder.Finally,Fourier transform infrared spectroscopy（FT-IR）,nuclear magnetic resonance spectroscopy(²⁹Si-NMR),gel permeation chromatography（GPC）,fluorescence electron microscopy and scanning electron microscope（SEM）were used to analyze the interaction mechanism between TEOS,rubber powder and original asphalt.The results show that Si-O-Si network structure is formed in rubber powder after hydrolysis and condensation of TEOS,which increases the swelling of asphalt to rubber powder and strengthens the reaction between rubber powder and asphalt,and limits the precipitation of carbon black in rubber powder.