Factor affecting the bond quality of functionally graded concretes produced with steel fiber and recycled aggregates

The combination of multiple layers to produce functionally graded concretes (FGC) creates an interfacial zone between layers named here as layer transition zone (LTZ). The LTZ can be considered similar to the overlay transition zone found in concrete overlays used to repair concrete structure. As the weakest link between concretes, the properties of LTZ can significantly influence the bond quality and mechanical behaviour of FGC. Thus, in this research, the effect of several factors in the bond quality of FGC incorporating steel fibres and recycled aggregates was studied. The experimental results indicate that the effect of type of aggregate and casting delay between each layer in the quality of the LTZ in the FGC studied is higher than the effect of the content of fibre. In addition, the FGC studied can be produced with a casting delay shorter than 24 h between layers without loss of mechanical performance, increasing the potential of large-scale production of lower loading capacity structures.