Study On Performance And Mechanism Of Composite Strengthening Agent Modified Asphalt Mixture

High temperature rutting and low temperature shrinkage crack are the main diseases of asphalt pavement,they will not only decrease the using function and service life of the asphalt pavement,but also seriously affect the driving quality and driving safety.For a long time,researchers can not find a way to eliminate these two diseases,just taking measures to decrease the negative influences of them in some extent.In view of the successfully applied of polymer and fiber in asphalt and asphalt mixture,this paper is attempting to combine these two materials into a new composite material which could be added to the asphalt mixture in dry-mixing method,hoping that this composite material could improve the high temperature stability and low temperature crack resistance of asphalt mixture at the same time.Firstly,through rutting test,bending test and freeze-thaw split test,this paper determined the improvement effect of different amount of composite strengthening agent on asphalt pavement performance.Secondly,asphalt binder tests such as three main indexes,Brookfield viscosity,Bending beam rheometer(BBR),Dynamic shear rheometer(DSR)etc.are taken to study the effect of the composite strengthening agent on asphalt binder.Thirdly,through changing factors such as aggregate diameter and preparation method,this paper studied the effect of composite strengthening agent on asphalt mixture.Finally,asphalt mixture testes such as uniaxial penetration test and shear test are taken to verify the modification law of composite strengthening agent.In addition,through statistical analysis of the national climate condition and referencing the concept of asphalt PG grade,this paper took a further division to the present climate division of asphalt pavement service performance,and adjusted the technical requirements of high and low temperature performance of asphalt mixture in different division,based on this,obtain optimum mixing amount of composite strengthening agent in diferent area with different climate condition.Through a series of laboratory testes,following conclusions are obtained:(1)After mixing the composite strengthening agent in asphalt mixture,significant improvement effect are found on the high and low temperature performance and water stability of asphalt mixture,when the mixing amount up to 0.6%,all pavement performances of asphalt mixture could meet the requirements of most area;(2)After mixing the composite strengthening agent,the temperature sensitivity of asphalt would be decreased,and the decreased degree is positively related to the mixing amount;(3)After mixing the composite strengthening agent,significant promote is found on the viscosity and the high temperature anti-deformation ability of asphalt,but meamwhile negative influence is found on the low temperature anti-crack ability;(4)Among the composite strengthening agent modified asphalt mixtures of AC-13,AC-16 and AC-20,AC-16 has the best pavement performance,namely,AC-16>AC-13>AC-20;(5)Composite strengthening agent modified SMA mixture has a good pavement performance,it shows that the composite strengthening agent inside the asphalt mixture palying a role of modified asphalt which is used in a conventional SMA;(6)After mixed into the asphalt mixture,the composite strengthening agent particles did not totally react with the asphalt,part of them were playing a role of reinforcement and filling to the aggregate in the particle form;(7)After mixing the composite strengthening agent,shear strength and penetrate strength of asphalt mixture have a significant improvement,it proved the improvement effect of composite strengthening agent on high temperature performance of asphalt mixture;(8)In view of the asphalt PG grade in research of SHRP,the present climate division of asphalt pavement performance could be futher divided;(9)In view of the present low requirements of high and low temperature performances of asphalt pavement in different climate division,which multiplied by relevant coefficient would be more reasonable,the coefficient of dynamic stability is 2,and the coefficient of dynamic stability bending failure strain is 1.1.