Effect of water-absorbent polymer balls in internal curing on punching shear behavior of bubble slabs

Abstract

The punching shear capacity of bubbled slabs is one of the main problems due to its decreased thickness; when there is inadequate curing, the problem becomes more critical, causing the building’s structural performance to deteriorate and exposing it to the risk of collapse. This study aimed to investigate the effect of using water-absorbent polymer balls in internal curing on the punching shear behavior of bubble slabs. Six concrete slabs were cast (1,000 mm × 1,000 mm × 70 mm). The main variables in this study are the type of slab (solid and bubble), type of curing (water and air), and ratio of water-absorbent polymer balls (5 and 10%). Studying the performance use of polymer balls and recycled plastic balls together and in normal strength concretes is limited. Also, investigating their behavior can provide insight into the efficiency of using these materials to improve concrete structures. Results showed that the most effective ratio for using polymer balls in internal curing is 5%, which had a good effect on the ultimate load, the first crack load, deflection, and crack pattern compared to the water-curing sample (reference sample). The water-absorbent polymer balls used in this study can absorb water when added to a concrete mixture. They release the water absorbed and subsequently contract, forming voids that are equivalent in size to the balls. This process facilitates internal curing while reducing the weight of concrete through the air voids left by the balls after they are dry.