Performance Evaluation of Recycled Aggregate Concrete Enhanced with Hooked Steel Fibers: Fresh and Hardened Properties

This study investigates the combined influence of Recycled Coarse Aggregates (RCA) and Hooked Steel Fibers (HSF) on the fresh and mechanical properties of concrete, aiming to achieve a balance between sustainability and structural performance.

Concrete mixes were prepared with RCA replacement levels of 0%, 25%, 50%, and 75%, while HSF was incorporated at volume fractions ranging from 0.0% to 1.0%. Fresh properties were assessed using slump tests, whereas compressive, flexural, and splitting tensile strengths were evaluated after 28 days to examine hardened behavior.

RCA incorporation resulted in notable reductions in mechanical strength due to increased porosity and weaker interfacial bonding; however, the addition of HSF effectively compensated for these losses. An HSF dosage of 0.4–0.6% was sufficient to recover compressive and flexural strength losses at 25–50% RCA, whereas 1.0% HSF was required to restore or surpass tensile and flexural properties at 75% RCA replacement. Slump values decreased with increasing fiber content, indicating reduced workability, but remained within manageable limits with the use of admixtures.

The findings highlight the potential of HSF to mitigate the strength reductions associated with RCA, thereby offering a balance between performance and sustainability suitable for practical applications.

With optimized HSF dosages, the mechanical drawbacks associated with RCA can be effectively offset, enabling the production of structurally sound and eco-friendly concrete for diverse construction applications.