Study On The Influence Of Steel Fiber And The Size Of Recycled Coarse Aggregate On The Impact Performance Of Recycled Concrete

Huge amount of construction waste has a serious impact on the ecological environment,not only occupying land resources,but also polluting the environment.The recycling technology of waste concrete can effectively recycle and reuse construction waste,and recycled concrete has become a hot issue in the field of engineering at home and abroad.The aggregate size of concrete has great influence on its basic mechanical properties and macro mechanical properties under dynamic load.The mechanical index of recycled coarse aggregate is worse than that of natural aggregate,which limits the application of recycled concrete in the field of structural components,so it is of great significance to optimize the mechanical properties of recycled concrete.At the same time,most of the existing research on recycled concrete is focused on the recycled coarse aggregate or fine aggregate with a single aggregate size range,ignoring the impact of the maximum size of recycled coarse aggregate on its mechanical properties.Therefore,this paper takes the maximum size of recycled coarse aggregate and the volume content of steel fiber as variables to study the coupling effect on the static and dynamic mechanical properties of steel fiber recycled concrete,so as to provide reference for the reasonable selection of coarse aggregate size and volume content of steel fiber in the promotion and application of recycled concrete.The main contents of this paper are as follows:(1)Experimental study on the basic mechanical properties of steel fiber recycled concrete.The compressive strength and splitting tensile strength of 12 groups of cube specimens with the size of 100 mm × 100 mm × 100 mm are tested.A calculation model for describing the compressive strength and splitting tensile strength under the coupling action of the volume content of steel fiber and the maximum particle size of recycled coarse aggregate is established.(2)Experimental study on impact performance of steel fiber recycled concrete.The drop hammer impact test method recommended by ACI544 Committee was used to test12 groups of recycled concrete round cake specimens.The failure mode of the specimen,the number of initial crack impact and the number of final crack impact are analyzed.The impact performance of SF-RAC is evaluated by three indexes: toughness coefficient C,ductility ratio ? and impact energy consumption after cracking.(3)Impact life estimation based on Weibull distribution model.The impact test results of steel fiber recycled concrete are analyzed statistically to obtain the impact times of initial crack and final crack of recycled concrete under different failure probabilities(0.1,0.15 and 0.3).The impact life of recycled concrete is estimated and analyzed to provide theoretical basis for further research on the impact performance of recycled concrete.(4)Based on the Weibull distribution model,the damage evolution equation is established.Based on the Weibull distribution model,the damage evolution equations of the compressive strength and the impact times of SF-RAC are established by using the statistical method of damage mechanics.The damage life of SF-RAC is analyzed under different damage variable values(damage degree).