Mechanical characteristics of ultra-high performance steel FRC made with recycled concrete aggregates

Abstract

Recycled concrete aggregates (RCA) are increasingly becoming a sustainable alternative to natural aggregate (NA) for concrete applications. This study, therefore, tests the influence of RCA on the fresh and hardened mechanical characteristics of six ultra-high performance fiber reinforced concrete (UHPFRC). The steel fibers incorporated were of micro straight and macro hooked end types. The volume fractions considered were 0% and 1%. The evaluation was carried out on the flowability, compressive strength, and flexural tensile strength. It was revealed that the flowability of UHPFRC was slightly affected by the coarse aggregate types. However, the flowability was decreased by 12% to 15% with steel fibers. The results also revealed that at a steel fiber volume fraction of 0%, RCA had little influence on the compressive strength, while they noticeably influenced the flexural tensile strength. In addition, steel fibers were shown to have a more noticeable influence on the specimens with RCA compared to those with NA. Furthermore, the flexural tensile strength of all specimens incorporating steel macro-fibers were significantly improved, regardless of the coarse aggregate type.