Research On The Performance Evaluation Method Of High Viscoelastic Expansion Joint Asphalt And The Effect Of Warm Mixing Modification

Bridge seamless expansion joints are widely used in foreign bridge projects due to their convenient construction,high driving comfort,easy maintenance,and low cost.However,seamless expansion joints have problems such as poor durability and short service life in actual use,which affect their further promotion and use in the country.Insufficient material performance of expansion joints,backward material evaluation indicators,and serious short-term aging of materials caused by excessive heating during construction are the main reasons for the poor durability of seamless expansion joints.The content of asphalt of seamless expansion joints is relatively high,and its overall performance mainly depends on the performance of the cement.In order to improve the performance of seamless expansion joints,it is necessary to select an evaluation method that can fully reflect its high and low temperature performance according to the characteristics of high viscoelastic asphalt for expansion joints and solve the problem of short-term material aging.In this paper,the basic performance and rheological performance evaluation test of three kinds of high viscoelastic asphalt with seamless expansion joints are carried out.The test characteristics and the test result indicators are comprehensively compared.The high and low temperature performance evaluation method of the high viscoelastic asphalt material for expansion joints provides a reference for selecting the type of cement.At the same time,warm mixing to reduce the construction temperature and reduce the short-term aging of the material modifies the expansion joint asphalt material.Based on the above theory,this research carried out related work and reached the following conclusions:(1)Due to the high polymer parameters of seamless expansion joint asphalt cement,the indicators adopted by current material specifications at home and abroad have defects in evaluating the performance of the material.The current softening point,ductility and other indicators cannot fully reflect the viscoelastic properties of the material.And high and low temperature performance.The viscoelastic characteristic index of the multi-stress creep recovery test takes into account the linear and non-linear viscoelastic state of the material,which can comprehensively evaluate the high temperature performance and elastic recovery performance of the seamless expansion joint asphalt.The low temperature stress relaxation test of the bending beam rheometer obtaining the low-temperature creep and stress relaxation properties of the material can more comprehensively reflect the working state of the material under low-temperature conditions,and the test results are closer to the results of the road performance of the mixture.(2)The high and low temperature test results of the three asphalt binders show that the average recovery rate of the BJ type expansion joint asphalt under high temperature conditions is 2%～5% higher than the other two binders,and the non-recoverable creep compliance is 10% lower.The high temperature resistance to deformation is better;at low temperatures,the 60 s creep stiffness modulus of the HN asphalt material is relatively lower,the240 s stress residual rate is higher,and the low temperature performance is slightly higher than that of the BJ type.Considering that the material use environment has higher requirements for high temperature performance,BJ type expansion joint asphalt is more suitable as a project asphalt material.(3)After the BJ type cement is modified by warm mixing,the order of cooling effect of the four warm mixing modifiers is measured as: ACMP-1>MW-1>Sasobit>Evotherm,combined with the high and low temperature properties of the modified material The MW-1type warm mixing modifier is selected for comprehensive evaluation.This material can reduce the mixing and compaction temperature of high viscoelastic asphalt cement by about10°C,and at the same time,it can improve the high and low temperature anti-deformation performance of the material,so that the cement can be more Well adapted to the working environment of expansion joints.The test index of multi-stress creep recovery test and the result index of low-temperature bending test of bending rheometer can better reflect the stress response state of high viscoelastic asphalt materials.The test results have high consistency with the mixture test and can be used for high viscoelastic asphalt.The high and low temperature performance of the cement.The test method is relatively simple and easy to operate,and the fluctuation range of the results is smaller.It is recommended to use it as a key control index for evaluating the high and low temperature performance of seamless expansion joint asphalt binder.The research results of the warm mix technology show that the MW-1 type warm mix modifier has a better viscosity reduction effect and high temperature performance improvement effect on high viscoelastic asphalt binders.It is recommended as a warm mix modifier additive for high viscoelastic asphalt binders.