Study On Preparation And Properties Of Nano High Viscosity Composite Modified Asphalt

In recent years,with the rapid development of road engineering construction in China,the number of bridge constructions has increased year by year.With its excellent pavement performance,high-viscosity asphalt is widely used in high-grade highways,bridge deck paving and some special projects.The high-viscosity asphalt in the market mostly uses high-volume SBS as the base material,which has the following problems:poor storage stability,severe attenuation of repeated heating performance,high-temperature asphalt viscosity,and poor workability in construction.In response to the above problems,this article uses two surface-modified carbon nanotubes and SBS modifiers to prepare a composite high-viscosity modified asphalt（CNTs/SBS-HVMA）.This product achieves the performance of traditional high-viscosity asphalt at the same time.It solves the problems of insufficient thermal storage stability,serious attenuation of repeated heating performance,and poor construction and workability.In order to explore the decay law of the storage stability of the traditional high-SBS content high-viscosity modified asphalt（SBS-HVMA）,thermal storage was carried out for 10days,and the conventional indexes,rheological properties and microscopic properties of asphalt samples with different thermal storage days were analyzed.Characteristic changes,discuss the performance degradation of the upper and lower samples after thermal storage.The results show that the difference between the upper and lower segregation softening points of SBS-HVMA is 35.4℃when the thermal storage is 2 days,and the segregation softening points difference is 34.2℃when the thermal storage is 4 days,and then it tends to be stable.In the first 2 days of thermal storage,the phase separation of high-viscosity asphalt coexisted with the development and swelling of the modifier,but phase separation was dominant;after 4days of thermal storage,the aging and degradation of the modified asphalt were dominant,and the performance was attenuated more obvious.In order to make up for the shortcomings of traditional SBS-HVMA,the nano-based high-viscosity composite modified asphalt with excellent performance was developed,and CNTs/SBS-HVMA were prepared by compounding two kinds of surface-modified CNTs and SBS modifier.SBS-HVMA and TPS high-viscosity modified asphalt（TPS-HVMA）were used as comparison samples,and their macroscopic and microscopic properties were analyzed.The results show that the optimal doping amount of the two CNTs in CNTs/SBS-HVMA is determined to be 1.0%;the segregation softening point difference of CNTs/SBS-HVMA is1.2℃（<2.5℃）,and the storage stability is much better than that of SBS-HVMA（segregation softening point difference of 35.4℃）and TPS-HVMA（segregation softening point difference of 11.1℃）;CNTs effectively improve the high temperature performance of modified asphalt and slow down the attenuation of viscosity;adhesion of CNTs/SBS-HVMA to aggregate.It has the best performance and its ability to resist water damage is improved;CNTs can increase the swelling area of SBS,make the SBS network denser,increase the elastic component of asphalt,and improve the pavement performance of asphalt.In order to study the high-temperature flow characteristics and medium-low temperature creep characteristics of the three high-viscosity asphalts,based on the principle of rheology,the high-viscosity asphalt was subjected to rotational viscosity test,dynamic shear rheology test and bending beam rheology test.The results show that:CNTs/SBS-HVMA has the lowest high-temperature flow viscous resistance and the best construction and workability;SBS-HVMA has the best high-temperature performance,TPS-HVMA is the worst,CNTs/SBS-HVMA is somewhere in between;Under creep conditions,CNTs/SBS-HVMA has the largest R and the smallest J_nr under different stress levels and different aging conditions,indicating that its high temperature resistance to deformation is the best.The reason is that CNTs act as short fiber reinforcement between the asphalt and SBS.It enhances the bond strength of the asphalt system;the low-temperature creep stiffness modulus CNTs/SBS-HVMA is the largest,followed by SBS-HVMA,and TPS-HVMA is the smallest,but the low-temperature creep rate values of the three are close,and they are all at the same low-temperature grade PG-28,shows that the addition of CNTs has no obvious effect on its low temperature performance.In order to verify the pavement performance of CNTs/SBS-HVMA mixture,indoor rutting test,freeze-thaw splitting test,trabecular bending test and Hamburg rutting test were performed,and compared the results with SBS-HVMA mixture and TPS-HVMA mixture.The results show that the three high-viscosity asphalts all have good high and low temperature performance and water damage resistance performance,indicating that the addition of CNTs can significantly improve the high-temperature performance of the asphalt mixture,and has little effect on the low temperature performance,and the performance of the mixture is similar to that asphalt performance is consistent.