Punching shear behavior of Lightweight foamed RC slabs

ABSTRACT This paper presented an experimental study on the Punching Shear Behavior of self-compacting Lightweight Concrete (LWC) Slabs. LWC was obtained through the use of polystyrene foam as a partial aggregate's replacement to reduce the concrete dry unit weight from 23.0 kN/m3 to 18.5 kN/m3. Nine medium scale RC slabs were statically tested to failure under concentric punching loading. The concrete type, slab's thickness, amount of shear reinforcement and loaded plate area were the test parameters. A comprehensive presentation of the experimental procedures, testes and results is undertaken in the paper, followed by a general discussion of all results. Finally, the punching shear capacities were obtained from the test results and compared with the calculated values from the available codes’ equations. Test results showed that the use of LWC in RC slabs resulted in most pronounced post-cracking structural degradations, including reduced stiffness until failure and reduced capacity but increased deformability relative to the normal density concrete (NDC) slab. The LWC slab's degradations were overcompensated through increased thickness, where increased capacity was achieved, but at the price of deformability reductions. Increasing loaded plate area or providing shear studs as shear reinforcement resulted in considerably improved structural behavior and increased post-yielding stiffness of slabs' responses as well as increased failure loads and increased failure deflections relative to LWC slab.