Experimental Study On Flexural Behavior Of Steel Fiber Recycled Concrete Beams

Recycled concrete means that the waste concrete block is crushed,washed and sieved to form recycled aggregate,and then the aggregate is partially or completely replaced by natural aggregate to make recycled concrete.The research and promotion of recycled concrete technology can effectively solve the problem of stacking of demolition and construction waste,realize the recycling of building materials,and have a good application prospect.Due to the defects of the recycled aggregate itself,the interior contains a large amount of mortar and cracks,resulting in the degradation resistance and durability of the recycled concrete structure thus produced is lower than that of the ordinary concrete structure.As a basic form of engineering,concrete beam is very necessary to study the mechanical properties of recycled concrete beams.At the same time,in order to make up for the natural defects of recycled aggregates,steel fiber is added to recycled concrete to improve its pull performance resistance.At present,domestic and foreign scholars have achieved certain results in this area,but the results have not been unified.The work of the thesis mainly includes the following aspects:(1)In order to carry out the bending performance test of steel fiber recycled concrete beams,five recycled concrete simply supported beams were designed and fabricated,including one ordinary recycled concrete beam and four steel fiber recycled concrete beams with different contents.The test beam was loaded at two points until it was destroyed,and relevant test data such as cracking load,ultimate load,deflection and crack distribution of the test beam were obtained.Based on the experimental data,the bending capacity of the steel fiber recycled concrete beam,the maximum crack width and the control section deflection are analyzed.The test results show that the steel fiber recycled concrete beam basically conforms to the flat section assumption during the stress process;its load-deflection curve is similar to that of ordinary recycled concrete beam;the incorporation of steel fiber can better inhibit the development of crack;the increase of steel fiber The toughness effect is obvious,and the ductility of the steel fiber recycled concrete beam is significantly improved.(2)Based on the experimental data,the finite element analysis software was used to simulate the bending behavior of five test beams.The analysis results show that the calculated values agree well with the experimental values.On the basis of this,the finite element expansion analysis of the mechanical properties of steel fiber recycled concrete beams is carried out with the longitudinal reinforcement tensile reinforcement ratio and concrete compressive strength as parameters.The results show that the reinforcement ratio mainly causes cracking of steel fiber reinforced concrete beams.The post-stress performance has a great influence;The compressive strength of concrete is from C30 to C50,and the ultimate bearing capacity of steel fiber recycled concrete beams is increased by 6.8%.Through the orthogonal analysis numerical analysis,the comprehensive influence of the bending behavior of 16 steel fiber recycled concrete beams was studied.Based on different investigation items,the corresponding recommended optimal ratio was proposed.(3)Based on the results of the above research and analysis,the calculation method for the ultimate state of the normal section bearing capacity of steel fiber recycled concrete beams is proposed.The Code for Concrete Structure Design and the Technical Specification for Fiber Concrete Structure.Based on the relevant calculation formula,the calculation formula of ultimate bearing capacity of steel fiber recycled concrete beams is proposed.(4)According to the test results,the crack control calculation and the deflection test of the flexural members are carried out on the normal use state of steel fiber recycled concrete beams.Based on the data and related calculation formulas,the calculation formula of the maximum crack width and deflection of steel fiber recycled concrete beams is proposed.