| The common asphalt has been unable to adapt to road performance with the increasing of traffic and loads.SBR,waste tire rubber powder and other polymers have been used as modifier to improve the performance of asphalt,which had a positive effect on preventing pavement early disease.While using large amount of modified asphalt not only makes the price of polymer modifier rising but also has many diseases such as rut,low temperature cracking etc.herefore,it has become one of the main work focus to develop better performance and more effective economic benefits of new modified asphalt for road materials practitioners.In this paper,polyphosphoric acid modified asphalt and polyphosphoric acid / SBS composite modified asphalt with different polyphosphoric acid content were prepared by using SK90 and Zhenhai 90 asphalt.High temperature performance and temperature susceptibility of different types and polyphosphoric acid content asphalt were analyzed by repeated creep elastic recovery rate,cumulative strain,creep strength modulus of the viscous part and temperature scanning test.It is found that polyphosphoric acid can significantly improve the elastic recovery rate of asphalt,reduce the sticky part of cumulative strain and creep stiffness,improve the temperature and reduce the permanent deformation of asphalt under repeated load.The modification effect of polyphosphoric acid on SK90 asphalt was better than that of Zhenhai 90.The modulus Sand creep rate m of polyphosphoric acid modified asphalt and its composite were measured,and the low temperature performance were analyzed by rheological test in different temperature.The results showed that the creep modulus S of polyphosphoric acid modified asphalt and its composite increases with the increase of polyphosphoric acid content,especially when the dosage is more than 1.5% While the creep rate m decreases with the increase of polyphosphoric acid content.The addition of polyphosphoric acid has a negative effect on the performance of low temperature crack resistance of asphalt.The RTFOT and PVA were carried out on polyphosphoric acid modified asphalt,polyphosphoric acid / SBS composite modified asphalt and SBS modified asphalt respectively,and the variations of complex modulus and phase angle of different aging methods were analyzed.And the rules of asphalt molecular weight and dispersion coefficient during aging was analyzed by gel permeation chromatography.The results showed that the complex modulus of asphalt increases and the phase angle decreases,but with the increase of polyphosphoric acid content,the corresponding index decreases.Therefore,the polyphosphoric acid can improve the anti-aging properties of asphalt.AC-13 mixture was choosed as the sample of SBS,polyphosphoric acid / SBS composite and polyphosphoric acid modified asphalt.the dynamic stability of different asphalt mixtures,the maximum bending strain at low temperature and the Marshall test was analyzed by those samples.And the effect of polyphosphoric acid on the pavement performance of asphalt mixture was studied.The results showed that the effect on the dynamic stability was comparable of the 1.5% content of polyphosphoric acid and 4.5% SBS modified asphalt mixture,but the maximum bending strain at low temperature and Residual temperature of polyphosphoric acid modified asphalt is smaller than SBS modified asphalt. |
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