Experimental Study On Punching Shear Performance Of Post-filling Coarse Aggregate Concrete Slabs

Post-filling coarse aggregate concrete has good mechanical properties and use value,and can be widely used as "green concrete" building material in building structures.After adding coarse aggregate,the skeleton action can be effectively improved,the occlusal effect between coarse aggregate can be formed in concrete to improve the compressive strength,and coarse aggregate can also improve the concrete volume stability.The replacement of coarse aggregate with the same volume fraction in ordinary concrete can reduce the usage of cement,and then reduce the project cost and environmental pollution.The construction technology of post-filling coarse aggregate can be applied to the pumping concrete construction field of super high-rise buildings.Because the coarse aggregate is mixed with the pumping concrete twice on the roof,the friction resistance between the concrete and the conveying pipe can be reduced during the pumping process,and the pumping efficiency and height can be improved.In this paper,the punching test of 16 post-filling coarse aggregate concrete slabs was completed.Under the conditions of different mixing ratio,reinforcement ratio and thickness of the slabs,vertical load was applied to the center of the concrete slabs until the punching failure occurred.Based on the experimental phenomena and data,the development and distribution of cracks in the bottom of concrete slab,the curve of punch shear-deflection,the strain of steel bar,the strain of concrete and the failure state of punch shearing are analyzed.The experimental results show that the impact shear bearing capacity of the post-filling coarse aggregate concrete slab is higher than that of the ordinary concrete slab,and the increase range reaches the maximum value when the coarse aggregate content is 20%.The phenomenon of the punching failure process of the post-filling coarse aggregate concrete slabs is similar to that of the conventional concrete slabs,and the punching cone is formed to blow out the bottom of the concrete slabs.The influence of different formula variables on the shear force calculation is obtained by comparing the calculated values of the plate shear force with the measured values in the Chinese code,the American code,the European code and the Japanese code.The calculated value of the code formula has high safety degree,and the post-filling coarse aggregate concrete slab meets the requirements of the design code under normal service load.The post-filling coarse aggregate concrete material can be used in the slab and column structure.On the basis of satisfying the good performance,the aggregate concrete can improve the punching bearing capacity of the slab and column structure,reduce the amount of cement in the concrete,reduce carbon emissions and protect the environment.It has important practical significance and far-reaching strategic significance for the sustainable green development of the building structure.