| The current asphalt modifier research emphases gradually turns to chemical modifier at home and abroad,while the traditional modifier is mainly polymer which has poor thermal stability,high cost and other shortcomings.Although polyphosphoric acid can improve the high temperature stability and fatigue resistance of the asphalt,but it is difficult to meet the pavement performance requirements of modified asphalt.In this paper,the matrix asphalt is modified by compounding both polyphosphoric acid and polymer modifier-SBS.At present,polyphosphoric acid compound SBS modified asphalt still has some aspects which need to be improved and completed,such as,the matrix asphalt quality selection,modifier mixing method and reasonable dosage,modified asphalt production technology and evaluation index system,in order to make polyphosphoric acid compound SBS modified asphalt can be widely used in the actual production.The main contents of this study include determining the optimal ratio of polyphosphoric acid and SBS,selecting appropriate matrix asphalt and modifying it with the modified modifier,comparing the merits on evaluation index of the modified asphalt between Penetration index evaluation system and Viscoelastic index evaluation system the viscoelasticity index.The polyphenolic acid compound SBS modified asphalt is prepared by using the base asphalt(Esso 90 #,Zhenhai 90 #,SK90 #)commonly used in Gansu Province.PPA and SBS modified asphalt were analyzed qualitatively and quantitatively from the conventional index,viscosity,dynamic shear rheometer(DSR)and infrared spectroscopy(FTIR)test by using orthogonal design method.And the influence of different components of modified asphalt on the performance indexes of modified asphalt is studied by means of mathematical statistics method.The evaluation index system of SBS modified asphalt was established,and the optimal formula of the polyphosphoric acid compound SBS modified asphalt was also determined.According to the optimal formula,determined how do the content and the effect of different matrix asphalt affect the performance of compound modified asphalt and determine the best substrate type matrix asphalt.Finally,relying on the Linhe-Baijiao section of the Beijing-Xingjiang Expressway,the polyphosphoric acid compound SBS modified asphalt prepared according to the best formula is used to pave the test section to analyze the economic benefits.The results show that: the properties of polyphosphoric acid(PPA),SBS,dibutyl phthalate(DBP)and extraction oil have significant impacts on the performance of modified asphalt.The performance changes of compound modified asphalt are not factors alone,but combination of multiple factors.Based on principal component analysis and Topsis method can know,the optimal mixing ratio of each component are: PPA 1%,SBS 3.5%,extraction oil 2%,DBP 1%.Based on the optimal proportion of the formula,the effect of different matrix asphalt cultivars under different dosage of PPA is analyzed,and the reasonable amount of polyphenolic acid is optimized.The tests show that the type of matrix asphalt plays an important role in the performance of polyphosphoric acid with SBS modified asphalt.The reaction of SK90 # matrix asphalt with 3.5% SBS and 1% PPA polyphosphoric acid is more obvious than that of Zhenhai and Esso;and the corresponding composite modified asphalt performance is the best,Esso 90 # times,Zhenhai 90 # corresponding to the worst of the modified asphalt.The evaluation index system of the penetration index is more cursory than the viscoelastic index system,and the viscoelasticity index analysis is more accurate and straightforward.According to the best formula,polyphosphoric acid compound SBS modified asphalt has low cost and good economic and social benefit. |
