| Recycled Aggregate Concrete(RAC for short)is a “recycled aggregate” obtained by crushing,cleaning,and grading waste concrete blocks,and is a concrete prepared as part or all of coarse aggregate instead of natural coarse aggregate.Recycled aggregates mainly come from the demolition of old houses.Considering that the average annual waste concrete produced in our country is about 800 million tons,and there is a gradual increase trend,the environmental problems caused by this inhibit the sustainable development of our country’s economy.Therefore,this article starts from the perspective of sustainable development and fits the fabricated structure,and carries out research on the application method of recycled concrete in prefabricated building slabs.The research has high social and academic value.In this paper,recycled concrete and profiled steel plates are used in combination to develop a new type of prefabricated prefabricated concrete floor slab.In order to systematically study the flexural load-bearing performance of the new prefabricated prefabricated concrete floor slab,the following research work has been carried out: Designed and manufactured three new recycled concrete precast laminated floor slabs,four new ordinary concrete precast laminated floor slabs,three recycled concrete precast laminated bottoms and three ordinary concrete precast laminated slabs to carry out the flexural bearing capacity test and study.The influence of the presence or absence of recycled concrete coarse bones and the presence or absence of post-cast concrete superimposed surface layer on the flexural bearing capacity,profiled steel plate strain and concrete strain of the new laminated floor.The study found that:1.Three new recycled concrete precast laminated floor slabs,four new ordinary concrete precast laminated floor slabs,three recycled concrete precast laminated floor slabs and three ordinary concrete precast laminated floor slabs were designed and manufactured for bending bearing capacity test.The influences of the addition of recycled coarse aggregate and the laminated surface layer with or without post-cast concrete on the flexural capacity,the strain of profiled steel plate and the strain of concrete of new precast laminated floor slab were studied.The results showed that,the crack resistance and ultimate flexural bearing capacity of the new type of recycled concrete laminated floor were basically the same as those of the new type of ordinary concrete,indicating that recycled concrete can replace ordinary concrete for actual construction use,and show good construction performance.The ultimate flexural bearing capacity of the specimen with the post-cast concrete laminated surface is greatly improved compared with the specimen without the post-cast concrete laminated surface,and the increase rate is about 50%,Which showed that the open profiled steel plate with indentation were feasible as the shear key of the laminated floor.2.The ABAQUS finite element analysis software were used to numerically simulate the new concrete prefabricated prefabricated prefabricated floor slab and the prefabricated prefabricated floor,which showed that simulated load-mid-span deflection curve were in good agreement with the experimental curve.Further more,the thickness of the profiled steel plate and the laminated floor,the span of the laminated floor,the yield strength of the steel bar,the reinforcement ratio of the longitudinal steel bar,the strength grade and the replacement rate of the recycled concrete were analyzed.The study found that increasing the thickness of the laminated floor,reducing the span of the laminated floor,and increasing the ratio of longitudinal steel reinforcement can increase the ultimate flexural bearing capacity of the new precast laminated floor and the precast laminated floor,and the increase is between 10% and20%.Increasing the thickness of profiled steel plates,the yield strength of steel bars,and the strength of recycled concrete can also increase(2%-6%)the ultimate flexural bearing capacity of the new prefabricated laminated floor and prefabricated laminated floor.Under the same concrete strength level,the replacement rate of recycled concrete has almost no effect on the ultimate flexural bearing capacity of the new precast laminated floor and precast laminated floor.3.The new precast laminated floor were proposed in the first stage(construction stage)and the second stage(normal use).Comparing the calculation results of the formula with the test and finite element results,it was found that in the first stage(construction phase),The calculated value of the calculation formula for the bending bearing capacity of the normal section derived from the compression of the upper flange of the steel plate and the tension of the lower flange was in good agreement with the test value.In the second stage(normal use stage),when the prefabricated composite bottom plate and the composite surface layer form a whole joint force,the calculated values of the flexural capacity of the normal section derived from the formula considering the tensile action of the lower flange of the profiled plate and part of the web section but not considering the compressive action of the upper flange of the profiled plate are in good agreement with the experimental values.The calculated value of the calculation formula for the bending bearing capacity of the normal section of the first stage and the second stage of this new type of laminated floor was less than the test value,and has a certain safety reserve.The stiffness calculations of the first stage(construction stage)and the second stage(normal use stage)of the new laminated floor slab can adopt the stiffness calculation suggested in the "Specification for Design of Concrete Structures"(GB50010-2010)Formula.When calculating the mid-span deflection using the relevant formula,it was found that the theoretical calculation value was in good agreement with the experimental value or the finite element analysis value. |
PDF Full Text Request