Shear behaviour of large-scale rubberized concrete beams reinforced with steel fibres

The present work was conducted to investigate the influence of crumb rubber (CR) with/without steel fibres (SFs) on shear behaviour and cracking of large-scale self-consolidating and vibrated concrete beams with no shear reinforcement. Twelve beams were developed with variables including different replacement levels of fine aggregate volume by CR (0%-35%), SF volume fractions (0%, 0.35%, and 1%), and SF lengths (35 and 60 mm). The fresh and mechanical properties of the developed beams' mixtures were measured, and the performance of the tested beams was evaluated based on cracking behaviour, ultimate shear load, post-diagonal cracking resistance, and toughness. In general, increasing the CR content from 0% to 25% in self-consolidating concrete (SCC) showed a negative impact on their fresh and mechanical properties, ultimate shear load, post-diagonal cracking resistance, and toughness of the tested beams, but showed an improvement in the deformability and self-weight of concrete. However, optimizing acceptable SCC mixtures with CR and SFs alleviated the reductions in strength that resulted from adding CR and significantly improved the beams' toughness, ductility, and cracking behaviour. Since the challenge to optimize mixtures with high flowability and passing ability was not a factor in developing vibrated mixtures, it was possible to develop vibrated rubberized concrete mixtures with higher percentages of CR and SFs, providing beams with further improvement in ductility, ultimate shear load, deformability, toughness, and with further reduction in self-weight.