Punching shear behavior of reinforced concrete flat slab column connection containing recycled eggshell powder

Abstract

Every day, millions of bio-waste eggshells are discarded in the environment by poultry farms, homeowners, bakeries, and the food industry around the world. The possibility of recycling eggshells as a cement replacement in concrete may solve the disposal issue of eggshells. Also, cement production causes the release of carbon dioxide, which contributes to global warming. Replacing cement with eggshell powder (ESP) reduces the level of cement production and indirectly decreases carbon dioxide emissions into the atmosphere. This paper aims to investigate the structural effect of the ESP content as a cement replacement on the punching shear behavior of reinforced concrete (RC) flat slab column connections. The possibility of ESP reuse in RC flat slab structures tested for punching shear was investigated. Four well instrumented RC flat slab column connections (S1, S2, S3, and S4) were cast using four different concrete mixtures containing 0, 5, 10, and 15% ESP, respectively. The slab panels (620x620x50) mm with a constant square column size of (100x100) mm were simply supported and tested under concentrated column load. The test results of different concrete mixes made with ESP content are reported. The test results of RC flat slab behaviors, including failure mode, load–deflection response, load-corner rise, load–strain curves, load-edge rotation response, punching perimeter, angle of punching, shear load, ductility, and stiffness of tested slab panels with and without ESP are discussed. The experimental punching shear load and punching perimeter were compared with those obtained by code model equations in ACI, BS, and Eurocode. It can be concluded that the experimental shear load and stiffness for the slab containing 10% ESP content increased by 5.85% and 24% than that of the control slab without ESP. Eggshell powder could be applied to a certain extent to replace cement in the RC flat slabs.