Punching shear behaviour of full-scale slab-column connections cast from concrete with coarse recycled aggregate

Recycling demolition waste, such as concrete and bricks, offers significant environmental and economic benefits within the framework of sustainable development. Recycled concrete aggregate (RCA), produced from processed waste concrete, was traditionally used as a base or backfill material. However, extensive research over the past two decades has expanded its potential applications, including its use in structural concrete. A particularly promising use is in structural concrete for flat slab systems incorporating coarse recycled concrete aggregate (CRCA). This article presents the findings of an experimental program that investigated the punching shear behaviour of full-scale slab-column connections, with a thickness of 250 mm and cast using concrete with CRCA. A total of six slabs were tested, with two different bending reinforcement ratios: 0.52 % and 1.23 %. The slabs were cast using concrete with natural river aggregate (serving as reference slabs) and concrete with 50 % and 100 % CRCA replacement. Test results showed that using CRCA in concrete does not negatively impact the punching shear resistance of the slabs. For slabs with a reinforcement ratio of 0.52 %, the normalised punching capacities relative to the reference slab were higher by 7.4 % for 50 % CRCA and by 4.8 % for 100 % CRCA replacement. For slabs with a 1.23 % reinforcement ratio, the corresponding values were lower by 2.9 % and higher by 0.4 %, showing minimal variation.