Experimental Study On Shear Behavior Of Recycled Concrete Beams Under Different Fiber Volume Ratio

Currently the rate of urbanization of our country has accelerated noticeably and there is a huge consumption of resources in the process of expansion and renovation of the city, which causes great pressure to the environment.China has become the world’s largest economy by the end of 2014.The building materials consumption in China accounted for more than half of the world’stotal consumption. In the process of modernization of our country,there is still no strict controls of the use of resources and waste treatment.Relevant laws, regulations and policies are not perfect and the corresponding national technical specifications and procedures below normal. This phenomenon makesour natural environment be forced to bear the enormous pressure under vigorous development incivil industry of our country. In addition, the remained construction waste of the transformation of the city and the abandoned building caused by natural disasters both have great impact on environment. For example, the earthquake in Japan,2011 3.11, produced 16.28 million tons of garbage. Because of this the best way is to study how to put these construction waste to use again and to make waste profitable. Because of the aggregate of recycled concrete is derived from the waste concrete demolished from existing buildings and it has been eroded by the environment at first use and its material properties has been reduced. So in the use of the old concrete will face the problem that the strength of recycled concrete cannot do better than ordinary concrete. So the promotion of recycled concrete has encountered great difficulties.Steel fiber has good toughness and high tensile strength. The steel fiber concrete mixed with steel fiber and concrete has a very good improvement on strength, durability and crack resistance. The micro level structure of recycled concrete is similar to ordinary concrete.Both composed of aggregate and cementitious materials.Incorporating the steel fibers into a recycled concrete, using the excellent mechanical properties of steel fiber,the mechanical properties of recycled concrete will have a good improvement. If this method proved to be feasible after tests, it will change the civil engineering industry on the natural environment in vulgar consumption, which is of great significance for the protection and restoration of the natural environment.The test sets up three steel fiber recycled concrete beams. Strain gauge on the tension reinforcement and compression reinforcement, stirrups in steel fiber recycled concrete and on the surface of steel fiber recycled concrete. Determine the strain of steel and concrete at any time in the loading process and observe the characteristics of deformation and failure after loading, then study the mechanical properties of steel fiber recycled concrete with the data and phenomenon.The volume ratio of steel fiber as the variable, bearing capacity of steel fiber recycled concrete beams was calculated and analyzed. According to the fitting mathematical formula and relevant national standards, the law theory and computational methods of bearing capacity of steel fiber recycled concrete was summedOn the analysis of experimental results and test data, there are some main conclusions.(1) Under steel fiber ratio appropriate circumstances, steel fiber can influence the development of recycled concrete beam cracks effectively. If the steel fiber content exceeds the limit, it will reduce the adhesion between recycled concrete beam internal aggregate and the mechanical properties of the beam.(2) According to the three steel fiber recycled concrete beams test load applied process, observing changes of beam deflection, it can make a conclusion that resulting in elastic modulus of recycled concrete beams change by adding steel fiber, and the relationship between the changes of the content of steel fiber and elastic modulus of recycled concrete is a negative correlation with the maximum deflection of simply supported beam in mechanics of materials.(3) According to the depicting result of the principal stress tracing line of the unit body within the steel fiber recycled concrete beam that is loaded in this test, we found that the tendency of the principal stress tracing line of the unit body is different within different parts of the beam, and the change of that near the middle of the beam is relatively flat,while the change of that near the outside of the beam is relatively quickly. Especially the principal stress tracing line of the unit body that is in the left side of beams shear zone( when near the ends of the beam) changes most dramatically.(4) In the case of the same rate reinforcement and recycled aggregate replacement rate that is no more than 50%, with the increase of steel fiber content, the shear bearing capacity of steel fiber recycled concrete beams will decrease, and the relationship between them follows as 55755.17-2V?????.(5) According to the integral computation of deflection load curves for three steel fiber recycled concrete beam, We resulted that the beam which can absorb the most energy before destruction was the steel fiber recycled concrete beam with the steel fiber adding rate of 1%, the secondly was the beam with the steel fiber adding rate of 1.5%, and the least energy absorption was the recycled concrete beams with no steel fiber. That was because the steel fiber added in recycled concrete had effected the elastic modulus, thus the energy absorption effect of steel fiber recycled concrete was much better than that of the recycled concrete. And in the seismic action, the steel fiber recycled concrete showed better anti-seismic effect,. As the steel fiber adding rate continues to rise, the bearing capacity of steel fiber reinforced concrete turned to decline, and he total energy absorption of steel fiber recycled concrete decreased instead before destruction.