Influence of double hooked-end steel fibers and slag on mechanical and durability properties of high performance recycled aggregate concrete

This paper presents a study on the properties of sustainable high performance steel fiber-reinforced concretes that were manufactured with recycled concrete aggregates (RCA). Natural coarse aggregates were replaced by RCA derived from parent concretes with compressive strengths of 40 and 80 MPa at volume replacement ratios of 50% and 100%. High performance concretes (HPC) were manufactured using double hooked-end steel fibers added at a fiber volume fraction of 1%, and in some of the mixes 30% of ordinary Portland cement was replaced by slag. Along with their mechanical properties, the water absorption, electrical resistivity, and shrinkage of the concrete mixes were evaluated. The results indicate that HPC with desirable properties can be produced using RCA derived from a high-strength parent concrete. The addition of steel fibers significantly increases the mechanical properties of recycled aggregate concretes. Replacing natural aggregates with RCA of lower strength adversely affects the durability properties of the concrete. However, concretes produced with a higher quality RCA and those containing slag and steel fibers exhibit reduced water absorption and shrinkage compared to plain natural aggregate concrete. The findings of this research are highly promising for the development of HPC with reduced environmental impact.