Experimental Study On Flexural Behavior Of Recycled Steel Fiber-reinforced Concrete Beams

With the rapid development of China’s architecture industry,the increasing demand for building materials leads to the mining of vast natural resources,which consequently results in the destruction of ecological environment.A lot of construction waste will be generated in all the links of architecture industry ranging from construction to demolition of buildings.A lot of experimental studies have shown that all or part of the abandoned concrete blocks,after being appropriately treated,may replace the sand and gravels and other natural aggregates（mainly coarse aggregates）in concrete for re-configuring new concrete.However,compared with natural aggregate concrete,recycled aggregate concrete shows more obvious brittleness,as well as obviously declined anti-cracking capacity,which may cause bigger deflection and crack width of a flexural member and is disadvantageous to the seismic performance of a structure.,such as,used as building foundation bed,road base,etc.In order to solve the problem of low performance and poor crack resistance of recycled concrete structure,steel and steel fiber can be added into recycled concrete.In this test,we produced 8 test beams and set 2 basic variables,namely,the volume fraction of steel fiber and the replacement rate of recycled aggregate.The study covers the following items:1.The impact of steel fiber with various volume fractions（0,0.5%,1%,1.5%,2%）on the flexural behavior of composite beams under the premise of same aggregate replacement rate（100%）;2.The impact of recycled aggregates with various replacement rates（0,50%,100%）on the flexural behavior of composite beams under the premise of same volume fraction of steel fiber（1%）;Based on analysis of data collected during the loading process,such as beam deflection,cracks,concrete strain,rebar strain,I-bar strain,and mechanical property tests of structural concrete,major conclusions are obtained:（1）The bending mechanism for recycled aggregate concrete beams with steel fiber-profile steel is basically the same as that for the ordinary steel reinforced concrete beams.（2）The relationship among the volume ratio of steel fiber,the replacement ratio of recycled aggregateγ,and the axial compressive strength of steel-fiber recycled aggregate concrete is obtained based on mechanical property tests of concrete,as well as on the data analysis,as shown below,where,is the axial compressive strength of ordinary concrete without steel fiber.f_frck=（0.9576 + 0.1310 γ + 9.36）fck（3）Under the condition that only recycled aggregate is applied,steel fiber with volume ratio of 1%-1.5% can obviously improve anti-cracking performance of beams.The volume ratio of steel fiber and the replacement ratio of recycled aggregate have certain unremarkable influences on the load-bearing capacity of composite beams.