Experimental Study On Flexural Behavior Of Prestressed Self-compacting Recycled Concrete Beams

With the rapid development of the city,the increasingly serious waste concrete disposal crisis and the depletion of natural aggregate sources have both negative impacts on the ecological environment and not in line with the country's sustainable development strategy.Based on the performance advantages of self-compacting concrete and the energy-saving and environmental protection characteristics of recycled concrete,the application of self-compacting concrete in prestressed concrete beams can not only avoid the void caused by uncompacted concrete pouring,but also improve the durability and bearing capacity of bridge structures and extend the service life of bridge structures.Combining with the national natural science fund project "flexural performance of prestressed concrete high-performance recycled concrete bridge design theory research"(51608331),the type of concrete,the reinforcement ratio of non-prestressed,the number of prestressed reinforcement,composite reinforcement index and the strength of concrete under the influence of the prestressed self-compacting flexural performance of recycled concrete beams is studied and analyzed.The results show that:The failure forms and load-deflection curves of prestressed self-compacting recycled concrete beams are similar to those of prestressed ordinary concrete beams.The cracking load is less than that of prestressed ordinary concrete beam,and the cracking load has nothing to do with the ratio of nonprestressed reinforcement and CRI,Increasing the number of prestressed tendons can significantly increase the cracking load;The flexural capacity is the same as that of prestressed ordinary concrete beam.The crack width is smaller than that of prestressed ordinary concrete beam.The prestressed tendon reinforcement ratio,CRI,the number of prestressed tendons and concrete strength can effectively increase the flexural capacity The crack width increases with the increase of load level and decreases with the increase of non-prestressed reinforcement ratio.The deformation performance is better than that of the prestressed ordinary concrete beam,and the ductility coefficient decreases with the increase of the non-prestressed reinforcement ratio and CRI.Increasing the concrete strength of the test beam and reducing the number of prestressed tendons of the test beam can effectively improve the displacement ductility.The applicability of the crack load calculation formula,bending capacity calculation formula,short-term stiffness calculation formula and maximum crack width calculation formula provided by Chinese,American and European codes to the prestressed self-compacting recycled concrete beam is verified.Among them,the cracking load calculation formulas provided by the codes of China,America and Europe are not applicable.The crack load calculation formula of prestressed selfcompacting recycled concrete beam is proposed.Chinese specification of flexural bearing capacity,the short-term stiffness and maximum crack width calculation formula are used,and American specification provided by calculation formula is suitable for the calculation of maximum crack width,does not apply to the flexural bearing capacity and short-term stiffness,European specification provides the calculation formula is suitable for the short-term stiffness calculation,does not apply to the flexural bearing capacity and the maximum crack width.