Bond strength of FRP bars in recycled-aggregate concrete

This study presents an experimental program conducted to investigate the bond strength of FRP bars in recycled-aggregate concrete compared to the one in normal-aggregate concrete for better evaluation of the results. The experimental program contains thirty six specimens that are tested using the direct pull-out test. In this study, glass, carbon and basalt FRP bars are used with 12 mm diameter and bar bond length of 5d, where d is the bar diameter. The FRP bars are casted in different recycled-aggregate concrete strengths of 30, 45 and 60 MPa. The behaviour of bars in natural-aggregate concrete strength of 30 MPa is used as a benchmark and its behaviour is compared with the ones in recycled-aggregate concrete. The impact of the concrete strengths considered is identified based on the gain in the bond behaviour. The experimental results demonstrate the promise of the recycled aggregates as an alternative to natural aggregates in FRP reinforced concrete. In addition, the use of recycled aggregate enlarges the bearing friction behaviour between the FRP bars and concrete. Analytical models proposed in the literature for the bond behaviour of FRP reinforced concrete are compared with the experimental results obtained here. Organgun et al. equation, and the CMR and the BPE models can accurately predict the bond strength, and bond stress-slip behaviour, respectively, of FRP bars in recycled-aggregate concrete. (C) 2020 Elsevier Ltd. All rights reserved.