Research On The Preparation And Properties Of Epoxy Resin Concrete In Bridge Expansion Joint Transition Zone

The concrete service conditions in the transition zone of bridge expansion joints are poor,and it is extremely easy to damage under the reciprocating action of the driving load and the transmission force of the expansion device.The comprehensive performance of epoxy resin concrete is excellent,and it is suitable for the transition zone of bridge expansion joints.However,due to the high cost of epoxy resin concrete,the complex ratio design and construction technology,the application is limited.At present,it is used as the transition zone concrete research less.According to the service conditions of the concrete in the transition zone of the expansion joint,the performance index of the concrete in the transition zone was proposed,and high-performance epoxy resin concrete was developed.The main research contents and conclusions are as follows:By comparing the flexural strength and compressive strength of epoxy resin mortar,bisphenol A E-44 epoxy resin and phenolic amine T-31 curing agent suitable for preparing epoxy resin concrete were selected.The dense packing theory was used to optimize the aggregate gradation.When the distribution coefficient in the MAA model was 0.31,the minimum aggregate void fraction was 22.23%.By comparing the working performance and molding of epoxy resin concrete,the bone-binder ratio and the filling-binder ratio were preliminarily selected,and then the orthogonal test method was used to determine the appropriate mix proportion of epoxy resin concrete.The main mixture properties and mechanical properties of epoxy resin concrete at different ages were studied.The results showed that the prepared epoxy resin concrete had good working performance,fast setting and hardening,initial setting time was 40minutes,and apparent density was 2220 kg/m~3.Epoxy concrete not only had high early strength,but also the later strength would not shrink.The cube compressive strength,axial compressive strength,flexural strength,splitting tensile strength and bond strength at 3days age were 88.8 MPa,72.6 MPa,20.6 MPa,8.72 MPa and 2.65 MPa,respectively.The mechanical properties were all met the design requirements of concrete in the transition zone.The elastic modulus of epoxy resin concrete of different ages fluctuates in the range of 13.7 GPa～14.8 GPa.The aging resistance of epoxy resin concrete was studied.After accelerated UV aging and accelerated hygrothermal aging for 551.2 hours,the mechanical properties of epoxy resin concrete decreased,and the maximum decrease was 15.2%,which could still meet the design strength requirements.By using SEM,DSC,and ATR test methods,it was found that both of the two aging methods would cause the oxidation reaction of epoxy resin system and change the microstructure of epoxy resin concrete,but the mechanism was different.After UV aging for 551.2 hours,the glass transition temperature of cured epoxy resin increased by 7.26℃,the carbonyl content increased,and the hydroxyl content decreased.After hygrothermal aging for 551.2 hours,the glass transition temperature of cured epoxy resin decreased by 10.88℃,and the carbonyl content and hydroxyl content increased significantly.Under the same aging time,hygrothermal aging had a more significant impact on the mechanical properties of epoxy resin concrete.