Experimental Study On Interlayer Bond Performance And Influence Of Epoxy Asphalt Steel Bridge Deck Pavement Structure

Epoxy asphalt mixture has the characteristics of high strength,good durability and excellent fatigue resistance,etc.It is mainly used in steel bridge deck pavement engineering.The epoxy resin waterproof bonding layer bonds the steel bridge deck and the pavement layer,taking into account the waterproof effect,and has a significant impact on the performance and service life of the steel bridge deck pavement.The characteristics of orthotropic steel bridge deck and dynamic load of vehicles put forward higher requirements on the strength,high temperature stability and fatigue performance of epoxy waterproof adhesive layer.The application of epoxy resin bonding layer mainly refers to relevant engineering experience,material application guide,etc.The design and construction control indicators such as the thickness and construction time of the bonding layer in engineering applications lack theoretical basis and explanation.The influence factors of the interlayer interface morphology and bond strength of pavement structure are also lack of clear understanding.In order to carry out the design and construction control of the epoxy resin bonding layer more scientifically and effectively,it is necessary to analyze the integrated bonding composite interface system of the pavement layer,the bonding layer,and the steel bridge deck,and explore the methods to improve the strength of the composite interface.Based on the research of interlayer bonding morphology and mechanism of pavement structure,the influencing factors of bonding strength between pavement layer and steel bridge panel were evaluated by combining the rheological property in the process of binder curing,construction control and epoxy asphalt pavement mixture,so as to provide reference for improving the interlayer bonding strength of pavement structure.First,the basic properties of epoxy resin binder were analyzed.The contact and melting process between the bonding layer and the epoxy asphalt mixture pavement layer was studied based on the basic bonding theories.The microstructure of the cross section of the bonding layer and the pavement layer was observed and analyzed by stereoscopic microscope and scanning electron microscope.The cross-sectional morphology shows that the contact bonding between the bonding layer and the bottom of the pavement layer is not a theoretical plane.The bonding layer melts under the high temperature of the hot epoxy asphalt mixture,and penetrates into the mixture with the compaction process,forming 5-10mm thick composite“bonding interface area”,which is composed of complex factors such as epoxy asphalt,aggregates,voids and adhesives.The bonding area is distributed in a horizontal strip.The bonding force produces through physical occlusal and chemical bond formation,which forms the bonding strength between the steel bridge panel and the pavement layer.The viscosity of epoxy resin binder during the mixing process was evaluated by using a Brookfield viscometer.The results showed that the initial viscosity of the binder decreased with increasing temperature,and the viscosity growth rate increased with increasing temperature.Differential scanning calorimetry（DSC）was used to study the dynamic reaction heat of epoxy resin binder at different heating rates.The temperature of the curing reaction of the binder was determined by using the T–βextrapolation.The initial curing temperature T₀=47.7℃,the peak curing temperature T_max=83.5℃,and the final curing temperature T₁=123.8℃.Combined with the viscosity and DSC test results,considering the construction and workability,the suitable temperature range for the preheating of the bonding layer is 30-40°C,and the coating construction time is 35-45min.The dynamic shear rheometer（DSR）was used to evaluate the rheological properties of the epoxy resin binder.Studies have shown that the modulus of the epoxy resin decreases with increasing temperature and increases with the frequency of load.And the phase angle within the 30-90℃decreases with increasing temperature.Epoxy resins exhibit rubber-like elastic behavior,and the load frequency has no significant effect on the viscoelasticity of epoxy resins.The effects of the storage time of the adhesive material,the thermal shock of the pavement mixture and the stirring temperature on the performance of the adhesive layer were evaluated by the tensile test,drawing test and shear test of the bond layer.And the research shows that the storage time of the binder material should not exceed 1 year.The temperature of epoxy asphalt mixture should not exceed 190℃,and the mixing temperature of the binder material should be controlled at 30-40℃.The influence of diabase,granite and limestone aggregate on the crack resistance of epoxy asphalt mixture pavement layer was evaluated by trabecular bending test.Research shows that the use of high-strength aggregates can increase the crack resistance of the pavement layer,which is beneficial to protect the bonding layer and improve the service life.The drawing test and shear test were carried out on the bonding test piece of“steel plate-bonding layer-epoxy asphalt mixture”to evaluate the influence of the types of mixture gradation,compaction times and the coating amount of the bonding layer on the interlayer bonding strength of pavement structure.The research showed that the fine gradation and increasing compaction times of epoxy asphalt mixture can improve the interlayer bond strength.The coating amount of the epoxy asphalt mixture is in the range of 0.2-0.6 kg/m2,and the interlayer bond strength is not significantly different.The coating amount increased to0.8 kg/m2,which will reduce the interlayer bond strength.The failure interface morphology analysis shows that the mixture using fine gradation,increasing the compaction times and the appropriate amount of bonding layer can reduce the gap at the bottom of the pavement layer,improve the blending degree of the mixture and bonding layer,and increase the bonding strength between layers of the pavement structure.In the design and construction control of the epoxy resin bonding layer,the integrated design and construction control of the pavement layer and the bonding layer need to be comprehensively considered.The coating viscosity,coating amount,material storage timeliness,thermal shock and stirring temperature of the pavement layer significantly affect the performance of the adhesive layer.Using high strength aggregate can increase the crack resistance of pavement layer and reduce the delamination disease of pavement layer.The use of fine grading and compaction can improve the bonding strength between layers of pavement structure.The research results of this thesis can provide reference for the optimization design,construction control and engineering application of epoxy resin waterproof bonding layer for steel bridge deck pavement.