Structural behaviour of reinforced concrete beams containing crumb rubber and steel fibres

This paper presents experimental work to investigate the strength and cracking characteristics of optimised self-consolidating and vibrated rubberised concrete mixtures with/without steel fibres (SFs) using large-scale reinforced concrete beams. The test beams were cast with varying percentages of crumb rubber (CR) (0 to 35%), SF volume fractions (0, 0·35 and 1%) and SF lengths (35 and 60 mm). The performance of some design codes and published empirical equations was evaluated in predicting the shear capacity and first cracking moment of the tested beams. The results showed that the inclusion of SFs could alleviate the reduction in the shear capacity and first cracking moment that resulted from the addition of CR. In addition, combining CR and SFs contributed to developing sustainable concrete beams with high deformability, reduced self-weight and improved shear capacity. The composite effect of CR and SFs also helped to narrow the developed cracks and change the failure mode from brittle shear failure into ductile flexural failure, particularly for the SF volume of 1% (35 mm length). Comparisons of the predicted and experimental results indicate that most of the proposed equations can satisfactorily estimate the shear strength, but overestimate the first cracking moment.