Influence of low content of steel fibre on concretes produced with recycled coarse aggregates with varying densities

The use of construction and demolition (C&D) waste as aggregate in concrete results in a reduction in strength due to its porosity. To compensate, mix designs often require higher cement contents, which increase the material's environmental impact. This study presents an experimental and numerical analysis of the effect of steel fibres on the mechanical properties of the concrete produced with recycled C&D aggregates with varying densities. The variation in fibre content did not present any influence on the compressive strength of concrete, which is significantly affected by the lower density of the recycled C&D aggregate. The fibres collaborate to mitigate the loss of flexural strength of the steel fibre reinforcement in recycled coarse aggregate concrete (SFRRCAC) provoked by lower density of recycled aggregates when the water-to-cement ratio is lower. When the water-to-cement ratio is above 0.65, there is a great reduction of the matrix strengths due to the paste porosity and the influence of aggregate density and fibre content was insignificant.