Experimental Study On Mechanical Propertise Of Fiber Recycled Fine Aggregate Concrete And Seismic Performance Of Precast Composite Wall

With the rapid development of China's economy,problems like exhaustion of resources and constructon waste disposal appear.The method of completely or partly substituting recycled fine aggregate concrete for normal concrete in the frame grid of precast composite wall can not only relieve resources scarcity,solving the problem such as overrun with construction waste and pollution after they are abandoned,but satisfy the demand for ecological wallboard material in precast composite wall structure.This paper regards mechanical property of fiber recycled fine aggregate concrete and seismic performance of precast composite wall as the main line,using conclusions from uniaxial mechanical performance test of fiber recycled fine aggregate concrete and quasi-static test of precast composite wall,and systematically studies and discusses on issues such as the influence of substitution rate of recycled fine aggregate on mechanical property of fiber recycled fine aggregate concrete,a damage constitutive model for fiber recycled fine aggregate concrete and the seismic performance of precast composite wall.The main contents and results are as follows:1.The influence of water-cement ratio,sand ratio,replacement rate of recycled fine aggregate,the amount of fiber affecting the compressive strength and splitting tensile strength of fiber recycled fine aggregate concrete is studied by orthogonal experiment.The results show that: water-cement ratio is an important factor affecting the mechanical properties of fiber recycled fine aggregate concrete;Recycled fine aggregate contains many initial defects,making it more complex with the role of concrete,the incorporstion of recycled fine aggregate will adversely affect the mechanical properties of concrete;The effect of sand ratio and the amount of polypropylene fiber on thecompressive strength and splitting tensile strength of fiber recycled fine aggregate concrete is not significant.2.Based on the orthogonal experiment,this paper adopts the single-factor experiment to study the effect of the replacement rate of recycled fine aggregate on the mechanical properties of fiber recycled fine aggregate concrete,obtains the relationship between the important mechanical properties,the stress-strain curve and the damage constitutive model,and finally confirms the mixture ratio of fiber recycled fine aggregate concrete which replaces the normal concrete in the frame grid of precast composite wall.The results show that: with the increase of the replacement rate of recycled fine aggregate,the compressive strength,splitting tensile strength,axial compressive strength and the elastic modulus of fiber recycled fine aggregate concrete are reduced to different degrees;Based on the law of Weibull's statistical distribution and strain equivalent theory,the statistical damage constitutive model of fiber recycled fine aggregate concrete is established,the model can effectively reflect the tendency of fiber recycled fine aggregate concrete to tend to brittle with the increase of recycled fine aggregate.According to the analysis result of the cumulative damage evolution process,it is found that with the increase of the replacement rate of recycled fine aggregate,the deformation ability and toughness of the concrete are weakened,and the cumulative damage evolution inside the concrete is accelerated.3.Under low-cyclic horizontal loading,three kinds of precast composite walls with different material of the frame grid(normal concrete,fiber recycled coarse aggregate concrete,fiber recycled fine aggregate concrete)are studied in this paper,the seismic behaviors of those precast composite walls,such as bearing capacity,ductility,stiffness degradation and energy dissipation,etc.,are researched.A nonlinear numerical analysis model of precast composite wall is built by using ABAQUS software,and the accuracy of the numerical model is verified.Based on the effective numerical model,the effect of the replacement rate of recycled fine aggregate on the seismic performance of the precast composite wall is studied.The results show that:the overall performance of the precast composite wall is good,and the infilled blocks and the frame grid can fully play their respective roles and show good energy consumption performance;Compared with the normal concrete precast composite wall,the bearing capacity,the stiffnessdegradation and the energy dissipation capacity of the fiber recycled fine aggregate concrete precast composite wall are not significantly different,which means that the fiber recycled fine aggregate concrete at the low substitution rate can be a new type of wall material for the assembly of precast composite wall structure;With the increase of the replacement rate of recycled fine aggregate,the bearing capacity,rigidity and ductility of the precast composite wall are decreased in different degrees.