| With the improvement of bridge construction technology in China,the construction of long-span bridges has developed rapidly.In the construction of large bridges,the super-large steel-concrete composite girder bridge has gradually become a new bridge construction technology and has been widely used.Due to the increasing traffic load and complex climate environment year by year,in the design of bridge deck pavement of large steel-concrete composite girder bridge,the pavement material needs to have extremely high road performance,and must also have excellent bonding performance to ensure full bonding with concrete bridge deck,so as to achieve the effect of overall synergistic stress without damage,so as to ensure the safety and durability of bridge deck pavement system and prolong the service life.Comparing the advantages and disadvantages of commonly used pavement materials,SMA mixture has the advantages of mature construction technology,low cost and excellent road performance.However,the service life of SMA mixture designed by ordinary modified asphalt is low,which is difficult to meet the complex working environment requirements of steel-concrete composite girder bridge pavement.Therefore,this paper chooses instant high viscosity asphalt as binder to prepare SMA asphalt mixture as deck pavement material of large steel-concrete composite girder bridge.The mix ratio of instant high viscosity SMA asphalt mixture was designed,and its high temperature stability,low temperature crack resistance and durability were systematically studied.In this thesis,the Marshall compaction test and the gyratory compactor(SGC)compaction test are combined to design the instant high-viscosity SMA asphalt mixture based on the volume design method.Three types of SMA-10,SMA-13 and SMA-20 are designed.The better volume index is obtained by controlling the pass percentage of the key sieve,so as to determine the gradation of each mixture.The results show that the pass percentage of the key sieve of the three types of instant high-viscosity SMA mixture is 27.8 %,23.0 % and 23.7 % respectively.Marshall test was used to determine the optimum asphalt content of three types of instant high viscosity SMA asphalt mixture,which were 6.4 %,6.3 % and 5.8 % respectively.The test results meet the requirements of the specification.The rutting test and Hamburg rutting test were used to study the high temperature performance of instant high viscosity asphalt mixture.The effects of different nominal maximum particle size,temperature,asphalt type and other factors on the test results were investigated.The key indicators for evaluating the high temperature performance of the mixture were selected,and the correlation between rutting test and Hamburg rutting test was studied.The results show that the rutting resistance of instant high viscosity asphalt mixture is significantly higher than that of SBS modified asphalt mixture,and it has better high temperature stability.The dynamic stability of different types of asphalt mixtures increases with the increase of nominal maximum particle size,but the rutting depth of SMA-20 asphalt mixture is larger.With the increase of test temperature,the dynamic stability of instant high viscosity asphalt and SBS modified asphalt mixture gradually decreases,and the SBS asphalt mixture decreases more.Under the coupling effect of high temperature and dynamic water,the creep rate and rutting depth of instant high viscosity asphalt mixture are smaller than those of SBS asphalt mixture under all temperature,porosity level and nominal maximum particle size conditions.The influence of different nominal maximum particle size,asphalt type and asphalt content on the low temperature performance of the mixture was studied by low temperature trabecular bending test.The influence of temperature on the low temperature crack resistance of asphalt mixture was discussed by low temperature splitting test and IDEAL-CT test.The results show that SMA-10 and SMA-13 asphalt mixtures have better low temperature crack resistance than SMA-20,which is more in line with the requirements of low temperature crack resistance for steel-concrete composite bridge deck pavement.At-5 ℃,-10 ℃ and-15 ℃,the tensile strain and crack resistance index of instant high-viscosity asphalt mixture are greater than those of SBS asphalt mixture,indicating that the low temperature crack resistance of instant highviscosity asphalt mixture is better than that of SBS asphalt mixture.The freeze-thaw splitting test,the water immersion splitting test and the US AASHTOT283 test were used to investigate the water stability of fast-soluble,high-viscosity SMA mixes.The results show that the TSR values of SMA-10 and SMA-13 are greater than those of SMA-20,indicating that the water stability of the fine-grained mixes is better than that of the mediumgrained mixes.For the same maximum nominal particle size,the fast dissolving high viscosity SMA asphalt mixes have better water stability than the SBS asphalt mixes.The salt erosion resistance of fast dissolving high viscosity SMA mixes in coastal salt spray areas was investigated and compared with SBS asphalt mixes.Using the splitting strength of SGC specimens at 25℃ as the index,the effect of salt water erosion on the strength of asphalt mixes was investigated by the variation pattern of splitting strength of specimens at different ages under the test conditions.The results show that the damage of Na Cl solution on the splitting strength of the mixture mainly occurred in the first 7 d.Under the three test conditions of salt water immersion,salt erosion dry and wet cycles,and freeze-thaw cycles,the splitting strength of the fast-soluble high-viscosity asphalt mixture was higher,the SBS asphalt mixture was more severely affected by salt water erosion,and the fast-soluble high-viscosity SMA asphalt mixture had better resistance to water damage and salt erosion,and was more It is suitable for steel-composite girder bridge decks in coastal areas. |
