Experimental Study On The Flexural Behavior Of Steel Fiber Recycled Concrete Beams

In recent years, with the rapid development of China’s cities, the pressure on resourcesand environment which caused by “metabolism” on construction is also increasingly apparent.At present our country has become a big consumer of construction material, we have the mosthighly production and consumption of steel, cement and aggregates in the world, it not onlyconsumes a lot of energy and resources, but also causes serious damages to environment;besides, the construction waste which generated by the demolition of old buildingsaccumulating more and more and pile up like mountains, garbage "surrounding" cities hasseriously hindered the development of cities. Therefore, the re-use of construction waste is aimportant way for the sustainable development of cities in our country.Due to the defects of its material, the index such as strength and crack resistance,durability of recycled concrete are below to ordinary concrete, these defects makes its hard topromote the recycled concrete using on a large-scale in practical engineering. Through a lot ofresearch and engineering practice, we found that steel fiber reinforced concrete has a superiorcrack resistance, if adding steel fiber into the recycled concrete, it could make up theweakened on strength and crack resistance of concrete which caused by material properties ofrecycled aggregate, the realization of this vision will promote the widely use of constructionwaste in engineering and improve the utilization rate of recycled aggregates.Therefore, this paper based on a mechanics test of four steel fiber recycled concretebeams, which use the strain gauge to test the strain of the steel and concrete, and then researchthe characteristic of deformation and failure form of the components; by changing the steelreinforcement ratio and the replacement rate of recycled aggregates, to calculate and analysisthe factors which affecting the limit state of bearing capacity and serviceability; based on thetest data, refer to the “specification for design of concrete structures”(GB50010-2010) andthe "technical specification for fiber concrete structures”(CECS38:2004), discuss theapplicable calculation formula of bearing capacity,crack width and bending stiffness thatsuitable for the steel fiber recycled concrete beams.Based on the analysis of experimental phenomena and test data, this paper mainly got thefollowing conclusions:(1) In the flexural state, the destroy form of steel fiber recycled concrete beams is almostthe same with ordinary concrete, and the deformation law is mostly complied the planesection assumption.(2) To see its destruction process, all of the components has a appropriate reinforcementratio, except the L4, When the components have a certain steel fiber volume ratio and replacement rate of recycled aggregate, the flexural bearing capacity of beams increases withthe increasing of reinforcement ratio.(3) The weaken on normal section bearing capacity which caused by recycled aggregatewas related with the replacement rate of recycled aggregate, In the case of certain steel fibervolume ratio and reinforcement ratio, when the replacement rate of the recycled aggregate islower than50%, with the increase of recycled aggregate, the capacity of normal sectionchanges with the replacement rate of the recycled aggregate by the following relationship:M27.366.09, accordingly proposed suitable calculation method of flexural capacityfor steel fiber recycled concrete beams.(4) Based on the test data, refer to the “specification for design of concrete structures”(GB50010-2010) and “technical specification for concrete structures of fiber”(CECS38:2004)established the calculation method of crack width for steel fiber recycled concrete beams.(5)As the replacement rate of recycled aggregate increasing, capacity of bendingstiffness decreasing and c the following relationship:B (0.0653.4215）1012. And theratio of modulus of elasticity between steel fiber recycled concrete and ordinary concretechanges with the replacement rate of recycled aggregate by the following formula:0.010.854, and then established applicable calculation formula of bending stiffnessfor steel fiber recycled concrete beams.