Study On Mechanism And Performance Evaluation Of Composite Modified Asphalt For Pervious Asphalt Pavement In Semi-arid Area

With the rapid development of my country’s economy and rapid progress in highway construction,cities in semi-arid areas mainly use impervious asphalt or cement pavement,which brings negative impacts such as urban waterlogging,heat island effect,and reduced driving safety to the city.Permeable pavement is of great significance to alleviate the above problems,but its porosity is between 18%and 25%,which makes the pavement prone to aggregate scattering,pits and other diseases.Therefore,the permeable asphalt pavement composite modified asphalt is a guarantee for the permeable asphalt.The key to road performance.Mainly include the following content.First,the summer rainfall in semi-arid areas exceeds 60%of the annual rainfall,and the rainfall in some cities occurs at a probability of 30 to 50 mm within an hour,which aggravates urban waterlogging.The additives for preparing composite modified asphalt are selected as the line Type SBS,thermoplastic rubber high-viscosity agent,compatibilizer,stabilizer,and the processing technology for preparing composite modified asphalt is proposed,using controlled variables and orthogonal test,the formula is determined to be8%of compatibilizer,thermoplastic rubber The content of high viscosity agent is 6%,the content of SBS modifier is 8%,and the content of stabilizer is 0.2%.Secondly,the rheological properties of composite modified asphalt,base asphalt and SBS modified asphalt were tested.At 82℃,the high-temperature rutting resistance~*/4)9)of the original asphalt of the composite modified asphalt and the asphalt after RTFOT were respectively 2.53k Pa,2.86k Pa,at-24℃,the creep stiffness modulus of the composite modified asphalt is 279.5MPa,and the creep rate is 0.315.The results of high-temperature rutting test and small beam bending test show that the high-temperature performance and low-temperature performance of the composite modified asphalt are better.Then,the adhesion between the composite modified asphalt and the aggregate was evaluated by the boiling method and the ultrasonic soaking method.The boiling method grade was 5,and the ultrasonic soaking method asphalt wrapping rate was 85%.The water immersion Marshall test and freeze-thaw splitting test were carried out.The residual stability was 87.5%,and the freeze-thaw splitting strength ratio was 86.5%.The results showed that the composite modified asphalt has better adhesion to the aggregate.Finally,the finite element analysis of the composite modified asphalt girder shows that the difference between the simulated value and the test value is relatively small,indicating that the finite element simulation is an effective method to study the deflection law of the composite modified asphalt girder in the middle of the span.