Preparation Of PE & Desulfurized Rubber Compound Modified Asphalt And Analysis Of Its Modification Mechanism

As rubber asphalt is widely used,its defects such as easy segregation and high viscosity are increasingly prominent.The use of desulfurized rubber powder to prepare desulphurized rubber asphalt can not only improve the deficiency of ordinary rubber asphalt,but also improve the low temperature performance of asphalt.But the desulfurization rubber modified asphalt has obvious deficiency in the high temperature performance,which restricts its development and application.Polyethylene(PE)is a kind of asphalt modified material with good performance,especially the high temperature performance of asphalt is obviously improved.Considering the characteristics of these two modifiers,PE-desulfurized rubber modified asphalt is prepared by using desulphurized rubber powder and linear low density polyethylene(LLPE)as modifier,the composition and the best preparation process were determined,and the road performance of the composite modified asphalt and mixture was systematically studied,and the composite modification mechanism was explored.The main contents of this dissertation are as follows:(1)First,the Shell 70# matrix asphalt is selected.By a test method of controlling a single variable,the influence rules of two kinds of modifier content,particle size and preparation technology on the three major indexes of PE-desulfurized rubber composite modified asphalt were studied respectively.Finally,the preparation process parameters of PE-desulfurized rubber compound modified asphalt are as follows: First,under the conditions of shear rate 5000r/min,shear temperature at 170℃ ~180℃,the high speed shear 30 min of polyethylene with 2% mass fraction of matrix asphalt was added,then the desulphurized rubber powder with a mass fraction of 18% was added to continue the shearing of 45 min,and the 45 min was finally developed at 160 degrees to the bubble disappeared.That is to say,the PE-desulfurization rubber compound modified asphalt sample was prepared.(2)Secondly,the performance of PE-desulfurized rubber compound modified asphalt was evaluated from three aspects of asphalt conventional,rheological and aging properties.The results showed that the asphalt modified by the desulfurized rubber powder and polyethylene not only had good storage stability,low temperature flexibility,low viscosity and anti-aging properties of the desulfurized rubber asphalt,at the same time,its high temperature performance was significantly improved,and the hightemperature anti deformation ability was enhanced significantly.(3)Based on the above performance tests,the mechanism of the interaction between desulfurized rubber powder,polyethylene and asphalt is analyzed from a series of modern micro techniques from the perspective of modification mechanism.Fluorescence microscopy images show that the effect of desulfurization in composite modified with polyethylene powder,evenly distributed in asphalt modifier,and formed a fine powder uniformly dispersed in the polyethylene core structure around;infrared spectroscopy(IR)showed that the mechanism of desulfurization powder,polyethylene and asphalt is physical blending also,certain chemical reactions,two kinds of modified mechanisms exist and with the preparation time and temperature change;differential scanning calorimetry(DSC)showed that the composite modified asphalt has good temperature stability,while the glass transition temperature also confirms the low temperature performance of modified asphalt is good.(4)Finally,selection for SMA-13 and AC-13 type gradation for asphalt mixture design,respectively to determine the optimum asphalt content,and through high temperature rutting,low temperature bending,Marshall immersion and freeze-thaw splitting test of asphalt mixture high and low temperature performance and water stability test.The results show that both SMA-13 and AC-13 asphalt mixture has good performance at high and low temperature performance and water stability to meet the requirements of the specification.In contrast,the composite modified asphalt performs better in the SMA intermittent gradation.