Improved bending behaviour of steel-fibre-reinforced recycled aggregate concrete beams with a concrete jacket

This paper studies the flexural behaviour and ductility ratio of reinforced concrete beams made with steel fibres and coarse recycled aggregates (RAs) and strengthened after failure. Eight reinforced concrete beams (of 150 by 200 mm cross-section and 1500 mm span), with various transverse reinforcement spacings, were manufactured and tested. RAs from building demolition were used at 0% and 100% by mass to replace natural aggregates. Furthermore, steel fibres were added to improve the flexural behaviour of the beams at 0% and 2% (by volume). Both shear and flexural failures in a four-point bending test were analysed in specimens with various transverse reinforcement spacings. First, the specimens were tested to failure and then strengthened with a concrete jacket. In these tests, the flexural capacity, maximum displacement at mid-span and ductility before and after strengthening using the concrete jacket were measured. The effects of the steel fibres and of the transverse reinforcement spacing on the flexural behaviour of RA concrete beams, with and without a concrete jacket, were determined. Concrete jacketing is an efficient method for strengthening RA concrete beams, and when steel fibres, RA, and a combination of both were used, the ductility ratio increased by 160, 24 and 146%, respectively.