Study On Performance Of Geopolymer Modified Asphalt And Asphalt Mixture

Geopolymer has excellent properties such as high temperature resistance,acid resistance and high early strength.This paper attempts to use geopolymer as a new bitumen modifier to prepare geopolymer modified bitumen,and its basic performance,rheological properties,microscopic mechanism,micro morphology and road performance of modified asphalt mixture were systematically studied,aiming to explore a new type of modified bitumen.(1)Firstly,geopolymer was prepared,and its physical and mechanical properties were tested.Then,modified bitumen was prepared by mixing geopolymer with matrix bitumen.The influence of geopolymer on basic performance of bitumen was analyzed through conventional performance test of bitumen.The results show that: geopolymer modified bitumen has good storage stability and elastic recovery performance.The hardness,consistency,stiffness and brittleness of the bitumen mixed with geopolymer are increased,and the adhesion performance between bitumen and aggregate is enhanced.(2)The effect of geopolymer on the rheological properties of bitumen was studied by Brinell rotation viscosity test and dynamic shear rheological(DSR)test.The results of Brinell rotational viscosity test show that geopolymer can increase the viscosity of bitumen and improve the temperature sensitivity of asphalt.The results of DSR test show that geopolymer can effectively improve the deformation resistance,elastic recovery and permanent deformation resistance of bitumen,which is helpful to improve the stress sensitivity of bitumen.The exponential function model was used to analyze the relationship between the complex modulus of bitumen and temperature,which shows that the modified bitumen has high temperature sensitivity.(3)From the microscopic point of view,Fourier transform infrared spectroscopy and fluorescence microscopy were used to explore the micro mechanism and morphology of geopolymer modified bitumen.The results show that the geopolymer is mainly physical miscible and has weak chemical reaction.The geopolymer in the modified bitumen is uniformly dispersed and the micro phase state is stable.The change of the content of geopolymer will not affect the micro morphology.`(4)The road performance of modified asphalt mixture was studied from three aspects:high temperature stability,low temperature crack resistance and water stability.The results show that: with the addition of geopolymer,the dynamic stability increases significantly,the rutting depth decreases,the variation coefficient of dynamic stability decreases,and the high temperature stability performance is improved;residual stability and the ratio of freeze-thaw splitting tensile strength increases,the water damage resistance increases,and the water stability improves;the maximum bending tensile strain decreases,the bending stiffness modulus increases,and the low-temperature flexibility decreases,low temperature crack resistance is reduced.In addition,correlation analysis shows that rutting factor and average unrecoverable creep compliance can better evaluate the high temperature stability of asphalt mixture,and ductility can better reflect the low temperature crack resistance performance of asphalt mixture.(5)The curing time of geopolymer has no significant effect on the performance of geopolymer bitumen asphalt.Considering the influence of geopolymer on the performance of bitumen and asphalt mixture,the optimal content of geopolymer is determined to be 5%.