Study On The Performance Of PVA Fiber Reinforced Concrete And The Feasibility Of Its Application On Bridge Deck Pavement Leveling Layer

Bridge deck pavement is an important part of bridge structure.The cementconcrete bridge leveling layer is located between the bridge panel and the bridge deck pavement.It can adjust the design elevation,transfer the traffic load,and coordinate the deformation of the upper deck pavement and the lower deck.However,due to the insufficient attention paid to the bridge deck pavement structure in the design,the lax construction quality control,the repeated action of constantly increasing traffic loads,the harsh and complex use environment and other factors,the phenomenon of premature damage of the leveling layer becomes more and more serious,and then loses the supporting role of the upper bridge deck pavement,and loses the protective role of the bridge panel.Rainwater permeates into the bridge panels,resulting in corrosion of the steel bars of the bridge panels and a decline in bearing capacity,which threatens the safety and reliability of the bridge structure.At present,the commonly used material for leveling layer is ordinary cement concrete,its most prominent advantage is that it has a high compressive strength,but its bending and tensile strength is low,the deformation ability is poor,the toughness is poor,is a typical brittle material.As a result,it is very easy to have cracks and other diseases when it is used in leveling layer,which seriously affects the normal operation of bridge deck pavement.In recent years,many scholars have tried to add fiber to ordinary cement concrete in order to improve the bending and tensile strength,deformation ability and toughness of concrete.Traditional engineering cement base composite material(Engineered Cementitious Composites,ECC)can effectively improve the tensile strength of normal concrete is low,poor toughness shortcomings,but at the same time,factors such as its high price,raw material is not easy to get also limits the ECC materials applied in practical engineering.In view of the above problems,this paper uses domestic Polyvinyl Alcohol(PVA)fiber,which has obvious price advantage and reliable performance,to allocate fiber reinforced concrete suitable for bridge deck paving and leveling layer,studies and analyzes its performance,and explores whether it is feasible to apply it to leveling layer.The specific research of this paper is as follows:(1)PVA fiber concrete mix design.The use of domestic PVA fiber with obvious price advantage and reliable performance to replace the expensive imported fiber,the use of local river sand instead of ultra-fine quartz sand.According to the preliminary test of the research group,the mix ratio of PVA fiber reinforced concrete was optimized and improved on the basis of ensuring good water performance of the material,and the sand-binder ratio,water-binder ratio and water reducing agent dosage were determined.The influence of fly ash content and fiber volume rate on concrete performance was considered.On this basis,in order to be more close to the engineering practice,try to use coarse aggregate instead of a part of fine aggregate,and put forward a set of parallel test mix ratio.(2)Study on the performance of PVA fiber concrete.Tests on compressive strength,flexural strength,bending toughness,impact resistance,splitting tensile strength and interfacial shear strength of new and old concrete were carried out according to the performance requirements of the levelling layer material.The test results showed that:The addition of PVA fiber can effectively improve the brittleness of concrete,improve the bending strength,bending toughness,splitting tensile strength and impact resistance of the material,and ensure the performance requirements of the material used in the leveling layer.(3)Constitutive relation of PVA fiber concrete.In order to further study the deformation performance of the material,two groups of PVA fiber concrete were selected based on the performance test,and ordinary concrete was added as the control group to further study the constitutive relationship of the material.Axial compressive test and axial tensile test were carried out to measure the stress-strain curve of the material,analyze the curve characteristics,and calculate the constitutive equation of the material.(4)The feasibility of applying PVA fiber concrete to leveling layer was analyzed by finite element simulation.The three-dimensional finite element model was established by using the finite element software ANSYS to study the influence of the thickness and overload of the leveling layer on the stress of the leveling layer,and the difference of stress response between PVA fiber concrete and ordinary concrete when applied to the leveling layer was compared.The results show that compared with ordinary concrete,PVA fiber concrete can effectively reduce the normal stress of the levelling layer under vehicle load,with larger stress reserve,obvious cracking resistance,and can reduce the risk of delamination damage between the levelling layer and bridge panel,which has practical engineering application value.