Serviceability behaviour of FRP-reinforced slatted slabs made of high-content recycled aggregate concrete

At service load levels, shear-induced deflections of reinforced concrete (RC) slabs are small and therefore they are usually ignored in deflection calculations. However, shear-induced deflections can be large in RC slabs reinforced with Fibre Reinforced Polymer (FRP) bars, especially after the development of diagonal cracks. This article investigates the serviceability behaviour (deflections and crack widths) of FRP-reinforced slatted slabs cast with recycled aggregate concrete (RAC). Fifteen slabs were tested in flexure, including five slabs cast with normal concrete (NC), five slabs cast with RAC made with 50% recycled concrete aggregate, and five slabs cast with RAC made with 100% recycled concrete aggregate. The test results are compared to crack widths and deflection predictions given by current guidelines and Nonlinear Finite Element Analysis (FEA). The results show that, for the tested slabs with 100% recycled concrete aggregates, the predictions given by ACI 440.1R underestimate the experimental deflections by up to 30% at maximum load levels. Conversely, the sum of the flexural deflections given by Eurocode 2 and of the shear crack-induced deflections (calculated using a model proposed recently by the authors) match better the experimental deflections at both the onset of diagonal shear cracking load, and at the maximum load. The Concrete Damage Plasticity (CDP) model adopted in the FEA was found suitable to predict accurately the deformations of FRP RAC slabs. This study contributes towards the development of new more sustainable structural solutions for FRP RAC elements, as well as towards more accurate models to calculate their deflections.