Experimental Study On The Longitudinal Shear Behavior Of Steel-Recycled Coarse Aggregate Concrete Composite Slabs

Recycled aggregate concrete allows limited resources to be reused with significant social and economic benefits.The use of recycled aggregate concrete into the composite slab with relatively low performance requirements for concrete can promote the application of recycled concrete in practical engineering widely.The existing research shows that the introduction of recycled coarse aggregate has little influence on the bending capacity of the composite slab,and the current design method of composite slabs can be used.However,there are relatively few studies on the longitudinal shear behavior of recycled concrete composite slabs.In this paper,the shear-slip performance of the steel-concrete interface is studied by the pull-out test.Based on the full-scale test and finite element analysis,the influence of the parameters such as the replacement ratio of the recycled coarse aggregate on the logitudinal shear behavior are studied.The study includes the following three aspects:(1)A total of 17 sets 300 mm × 300 mm × 510/600 mm composite slab pull-out test are completed,and The influence of parameters such as the recycled coarse aggregate replacement ratio,water-to-cement ratio,thickness and type of the steel deck on the bondslip performance of the composite slab were studied.The test results show that under the parameters of this paper,with addition of 100% recycled coarse aggregate,the longitudinal shear capacity of the specimen can be reduced by 3.6%~20.0%.(2)A total of 4 different composite slabs with different replacement ratios of the recycled coarse aggregate and anchorage conditions are completed with two sixth-point concentrate loads,focusing on the full-scale specimen failure mode;loading point and mid-span deflection,relative slip of the steel deck-concrete interface and strain distribution of key sections,the effect of end anchoring and the recycled coarse aggregate replacement ratio on longitudinal shear behavior of composite slabs are studied.The test results show that the studs can effectively improve the longitudinal shear capacity of the composite slabs.The longitudinal shear failure occurs in the composite slabs without the studs,and the composite slabs with the studs are all subjected to bending failure.(3)Based on the bond-slip performance of the composite slabs under different parameters obtained by the pull-out test.The Radial-Thrust connection unit is used to establish a three-dimensional solid finite element model,and the finite element results are compared with the literature and the test results and both are in good agreement.On this basis,a parameter study is carried out.The result shows that when the studs are not configured,all the composite plates are longitudinally sheared and can be designed according to the m-k method.The thickness of the composite slab,the thickness of the steel deck and the shear-to-span ratio have a great influence on the longitudinal shear capacity of the composite slab.The water-to-cement ratio and the type of the steel deck have little effect on the longitudinal shear capacity of the composite slab,and the replacement ratio of the recycled coarse aggregate has little effect on the longitudinal shear capacity of the composite slab.When the end stud is configured,if the span of the composite slab is large,the diameter of the stud is large or the thickness of the steel deck is small,the composite slab is subjected to bending failure and the design of the recycled concrete composite plate can be carried out according to the calculation method of the standard bending capacity.