Study On The Properties Of TPU And APAO Composite Modified Asphalt And Its Mixture

TPU（Thermoplastic Polyurethane）is a block linear polymer formed by alternating hard segments composed of diphenylmethane diisocyanate（MDI）/toluene diisocyanate（TDI）and chain extender and soft segments composed of macromolecular polyols.With the characteristics of high strength,wear resistance and low-temperature resistance,TPU has been widely used in the shoe industry,clothes and other fields.In addition,TPU also has the dual characteristics of plastic and rubber.Therefore,using TPU as the asphalt modifier in the field of road engineering is a novel and effective method.TPU modified asphalt has good low-temperature performance,but the storage stability and high-temperature performance are relatively insufficient.As a low molecular weight amorphous plastic material,APAO（Amorphous Poly Alpha Olefin）can reduce the temperature sensitivity and effectively improve the high-temperature deformation resistance and storage stability of asphalt.Based on the characteristics of these two modifiers,this paper expects to make up for the defects of poor high-temperature and storage stability of TPU modified asphalt through h the addition of APAO,and the performance of TPU/APAO composite modified asphalt and its mixture through a series of indoor tests.The main contents are as follows:The optimum preparation process of TPU/APAO composite modified asphalt and the modification effect of different content of modifiers on asphalt were explored through the orthogonal test,conventional and rheological performance test.The results showed that the modified asphalt prepared by shear mixing matrix asphalt and TPU/APAO at 190℃and 5000 rpm for 60 min had better performance.After adding TPU/APAO into the asphalt,the penetration and ductility decreased,the softening point,elastic recovery and viscosity increased.In addition,on the basis of not damaging the low-temperature PG grade of TPU single modified asphalt,the addition of APAO further improved its elasticity,high-temperature resistance to permanent deformation,temperature sensitivity and aging resistance.Considering the modification effect of each content of modifiers,it was recommended that the optimum content of TPU and APAO were 2%and 6%,respectively.The compatibility and action mechanism between modifiers and asphalt were analyzed by storage stability,fluorescence microscope and Fourier transform infrared spectroscopy tests.The results showed that APAO could improve the distribution of TPU in asphalt and further ameliorate the storage stability of modified asphalt.In addition,APAO was physically miscible with asphalt,but the free isocyanate in TPU molecule would react with the polar carboxyl group in matrix asphalt,and its product was closely related to the formation of PU bond at 1750 cm^-1.The mixtures of 2%TPU,2%TPU+2%APAO,2%TPU+4%APAO,2%TPU+6%APAO and 70#asphalt with the optimum content of TPU were prepared,and the performance of different asphalt mixtures was explored through a series of indoor tests.The results showed that APAO could ameliorate the high-temperature performance of the asphalt mixture,and the greater the content,the more significant the effect.Compared with APAO,TPU was more conducive to the fatigue resistance of the asphalt mixture.In addition,2%TPU+6%APAO composite modified asphalt mixture showed superior high-temperature rutting resistance,low-temperature cracking resistance,water damage resistance and anti-aging ability.In conclusion,it was feasible to apply TPU and APAO composite modified asphalt mixture to pave asphalt pavement.