Detalhes do Documento

This paper presents results from the second stage of an extensive experimental programme investigating the punching shear behaviour of flat slabs made with coarse recycled concrete aggregate (CRCA). In this stage, five full-scale slabs (250 mm thick) supported by a square column were tested to failure. Three slabs were tested without shear reinforcement, including a reference slab with natural aggregate and two slabs with 50% and 100% replacement of coarse natural aggregate (CNA) by CRCA. Two additional slabs, both with 100% CRCA, were provided with high levels of shear reinforcement using studs and stirrups. All slabs had an identical flexural reinforcement ratio of 1.53% and failed by punching. The results of the third series (S3) in the second stage, complemented by data from two earlier series (S1 & S2) from the first stage, indicate that the use of CRCA does not adversely affect punching shear capacity. The average ratio of normalised punching strengths reached 1.048 for 50% replacement and 1.039 for 100% replacement relative to the reference slabs. For slabs with shear reinforcement and 100% CRCA, the increase in punching capacity relative to slabs without shear reinforcement was 1.991 for shear studs and 1.588 for stirrups, consistent with values observed for concrete with natural aggregate. Comparison of the punching failure zones showed similar behavior of the flat slabs with and without CRCA. The study shows the applicability of current design models from the relevant code of practice for predicting punching shear capacity of flat slabs cast with concrete containing CRCA.