Experimental Study On Permanent Deformation Of High Content Rubber Powder/SBS Composite Modified Asphalt Mixture

The complex natural climate environment and the increasing traffic volume have higher requirements for the road service performance.Asphalt concrete pavement is the most commonly used pavement type of Expressway in China,which has the advantages of good driving comfort and construction convenience.Rubber powder modified asphalt mixture is a composite material composed of rubber powder,asphalt,aggregate and voids.It is a new environmental protection road engineering material.It can not only consume a lot of waste tires,but also improve the road performance of asphalt mixture and extend the service life of the road.Based on the actual project of Taihang Mountain,this paper compares the viscosity reducing effect of HDPE and TOR on the 25% rubber powder/SBS modified asphalt,and finally selects HDPE as the viscosity reducing agent to prepare the 25% rubber powder/SBS modified asphalt mixture,and compares the technical performance with20% rubber powder/SBS modified asphalt mixture and SBS modified asphalt mixture.Through SPT simple performance test,the dynamic modulus and permanent deformation law of three kinds of rubber powder/SBS modified asphalt mixture are studied;the main curve equation of dynamic modulus is built by sigmoidal function;the permanent deformation prediction model of rubber powder/SBS modified asphalt mixture under repeated load is built based on modified Burgers model.The main conclusions are as follows:(1)The preparation method of high content rubber powder/SBS composite modified asphalt mixture was put forward.The technical properties of the mixture of 20%,25% rubber powder and SBS modified asphalt were compared and analyzed.The results show that the best content of HDPE is 4.5%.With the increase of the content of rubber powder,the penetration of modified asphalt decreased,the softening point increased and the ductility decreased,which met the technical requirements.(2)The road performance of three kinds of modified asphalt mixtures is compared and analyzed.The asphalt aggregate ratio of three modified asphalt mixtures was obtained by Marshall test,and the road performance was analyzed by water stability test,rutting test and impermeability test.The results show that the three meet the requirements of technical indicators.With the increase of the amount of rubber powder,the rutting resistance is improved,and the water stability and impermeability are strengthened.(3)In the dynamic modulus test,the dynamic modulus curves of three modified asphalt mixtures have the same change rule.The dynamic modulus decreases with the increase of temperature and loading frequency.The dynamic modulus of asphalt mixture will be improved by adding rubber powder.It will be more obvious at high temperature and high frequency.The higher the content of rubber powder is,the more the dynamic modulus will increase.(4)The main curve equation of dynamic modulus is constructed by S-function(sigmoidal function).The correlation coefficient is 0.99,and the fitting effect is good,which provides a reference for the value of structural layer modulus in the checking calculation of pavement structure.(5)Under repeated load,three kinds of rubber powder / SBS modified asphalt mixtures have basically the same permanent deformation law.With the increase of temperature and load,the permanent deformation of asphalt mixture increases.The addition of rubber powder is beneficial to improve the permanent deformation resistance of asphalt mixture,and with the increase of rubber powder,the permanent deformation resistance is also significantly improved.(6)Based on the modified Burgers model,the prediction model of permanent deformation of three kinds of rubber powder / SBS modified asphalt mixture under repeated load is constructed.The correlation coefficient is greater than 0.98,and the fitting effect is good,which provides reference for the actual road service life prediction.(7)The asphalt mixture with rubber powder shows better stability than ordinary SBS at high temperature,especially when the rubber powder content is increased,its high temperature performance will be further improved.