Study On Composition And Mechanical Properties Of PPA/SBS Composite Biomass Modified Asphalt

To reduce the cost and increase the thermal-stability of styrene-butadiene-styrene(SBS),polyphosphoric acid(PPA)/SBS/composite biomass modified asphalt was prepared considering the coupling advantages of PPA and bio-asphalt(BA).However,the lack of researches on composite theory,evaluation system,and performance hinders its application and popularization.Firstly,three commonly used petrol-asphalt in Gansu and two PPA with relative mass fractions of 105%and 115%were selected to explore the compatibility betweent different PPA and petrol-asphalt.It was found that PPA-modified asphalt has excellent anti-deformation performance in high-temperature,and the modification effect of 115%PPA is more significant than the 105%PPA.Then,the optimization model was established based on analytic hierarchy process and fuzzy mathematics theory,and Shell 90#asphalt and 115%PPA were optimized as raw materials for PPA modified asphalt.Secondly,PPA-SBS composite modified asphalt was produced in the form of PPA partially replacing SBS,and the bio-asphalt(BA)was introduced by different replacing ratio to mitigate the low-temperature performance the composite asphalt matrix.The addition of BA significantly improved the storage stability of SBS,but decreased the instant elastic response of the composite asphalt.The coupling effect of PPA and BA significantly improves the fatigue life(N_f)of the original asphalts.However,the N_fof the composite modified asphalt is lower than that of the original asphalt after long-term aging,but it is still comparable to the control asphalt at 2.5%strain level.In addition,esterification produced by the reaction of BA and PPA has a positive effect on the low-temperature performance of the composite modified asphalt.Thirdly,the accelerated aging of the asphalts was simulated by using indoor thermal-oxidative and ultraviolet(UV)aging test,the high-temperature rheological properties of the composite modified asphalt before and after aging were investigated by using multiple stress creep recovery tests and temperature sweep tests.At 3.2k Pa,the variation trend of elastic response of the composite modified asphalt after aging is better than that of the control asphalt.After PAV aging,the increasing rate of creep recovery of the 1%PPA+3%SBS+10%BA and 1.5%PPA+2.5%SBS+15%BA groups are 30.2%and 59.7%higher than that of the control asphalt,respectively.In addition,the complex modulus of1%PPA+3%SBS+10%BA group and 1.5%PPA+2.5%SBS+15%BA group after UV aging is lower than that after TFOT aging.Fourthly,the mechanism of PPA-modified asphalt and composite modified asphalt was explored by using methods for characterization of microscopic properties of materials,such as infrared spectroscopy,atomic force microscopy.PPA reacts with the active hydroxyl group in asphalt.The interaction between the chains after reaction with asphalt is more significant,since the 115%PPA has a longer molecular chain than the 105%PPA,which explains that the 115%PPA has a more significant modification effect on asphalt than the 105%PPA.In addition,PPA was grafted to BA molecules by phosphate ester bond,thus improving the spatial complexity of its molecules,leading to the improvement of crosslinking effect,and providing a part of the mechanical properties.Finally,the three kinds of composite modified asphalt and SBS modified asphalt were selected,and their mix ratio were designed using Marshall test.Then,the high-and low-temperature performance of each asphalt mixture were verified,and the results show that the reduction of SBS content had a significant impact on the rutting resistance of the composite asphalt mixtures,but they still had excellent rutting resistance.Except the SBS content of 2.5%group,the tensile strain of the other two groups of composite modified asphalt was not significantly different from that of the control group.