Study On The Normal Section Bending Performance Of Unbonded Prestressed Recycled Coarse Aggregate Concrete Beam

Recycled aggregate concrete is short for recycled concrete, which is refers to the concrete, mortar, stone, tile and other construction waste are crushed by mechanical or manual crushing after screening and washing, and then form recycled aggregate grading according to certain proportion, next part or the whole of them are instead of natural aggregate, and last join the cementing material, freestone, water, admixture into a new concrete. Recycled coarse aggregate is refers to the particles which particle size is greater than 4.75 mm while recycled fine aggregate is refers to the particles which size is not more than 4.75 mm. The current study of recycled concrete are mainly concentrated in the mix design of recycled concrete, the basic mechanical properties of recycled concrete, recycled concrete beams and columns mechanical performance, etc., the domestic study of prestressed recycled coarse aggregate concrete beam is still blank. In order to have a further understanding of unbonded prestressed recycled coarse aggregate concrete beam’s structural behavior, this article mainly conducts a study from the following several aspects:(1) In order to conduct the research of recycled coarse aggregate concrete’s c tensile and compressive properties test, the total design block in both groups, the first group of test blocks’ recycled coarse aggregate replacement rate was set as 0%, 30%, 50%, 70%, 100% for the parameter, the second block adds mesh polypropylene fiber on the basis of first set, and the rest of the parameters and conditions are the same. The results show that recycled coarse aggregate replacement rate has little impact on cube compressive strength and splitting tensile strength under the two kinds of mixture ratio of recycled coarse aggregate concrete; Mesh polypropylene fiber has a distinct influence on recycled coarse aggregate concrete cube compressive strength and splitting tensile strength increase, but it has a huge impact on the recycled coarse aggregate concrete cube compressive and splitting tensile failure pattern.(2) In order to study unbonded prestressed recycled coarse aggregate concrete beam’s mechanics performance test, recycled coarse aggregate replacement rate was set as 0%, 30%, 50%, 70%, 100%, and then designs 5 test beams to analyze the failure mode, the normal section flexural bearing capacity and deformation features, crack propagation and distribution and steel strand stress increment of the tested beam. The results show that recycled coarse aggregate replacement rate has no effect on unbonded prestressed concrete normal section flexural failure pattern; When the test beam reaches ultimate load, unbonded prestressed recycled coarse aggregate concrete beam mid-span deflection were greater than ordinary concrete beam; Unbonded prestressed recycled coarse aggregate concrete beam crack development situation is similar to that of ordinary concrete beam under the same load, the recycled coarse aggregate replacement rate has no effect on test beam maximum crack width; Unbonded prestressed joist steel stranded wire stress increment of recycled coarse aggregate concrete were greater than ordinary concrete beam.(3) Based on the above research results, this paper put forwards the calculation formula of the stress increment of prestressed steel strand when unbonded prestressing of recycled coarse aggregate concrete beams are under the condition of bearing capacity limit, establishing unbonded prestressed normal section bending bearing capacity calculation method of recycled coarse aggregate concrete.(4) According to Code for Design of Concrete Structures (GB50010-2010) requirements, this article verifies the accuracy of unbonded prestressed recycled coarse aggregate concrete beam stiffness and maximum crack width’s calculation.(5) This article conducts normal section flexural simulation of 5 test beams using finite element analysis software ABAQUS based on the measured data, the analysis results show that the calculated values are in good agreement with experimental values.