Influences of steel fiber shapes and contents on compressive strength, shrinkage, and creep of high performance concrete containing high volume ground bottom ash

• Increasing steel fiber content and using deformed fibers significantly affected flowability and drying shrinkage. • The optimal content of deformed fibers improved compressive strength, reaching up to 90 MPa at 90 days. • Steel fiber content and shape had no impact on the elastic modulus or instantaneous creep strain. • Increasing steel fiber content enhanced creep resistance of sustainable high performance concrete (HPC). This research investigated the effects of steel fiber shape and content on the flowability, compressive strength, shrinkage, and creep behavior of high performance concrete (HPC) incorporating 60% ground bottom ash (G-BA) and 10% fly ash (FA) as cement substitutes. Additionally, 30% coarse bottom ash (S-BA) was used to replace fine aggregate. Concrete mixes were reinforced with various steel fiber shapes (straight, crimped, and hooked end) at volumes of 0.5% and 1.0%. The results showed that increased steel fiber content, especially with deformed fibers (hooked-end and crimped fibers), reduced flowability but had a negligible impact on the early-age compressive strength. At the later ages, steel fiber content and shape notably decreased drying shrinkage, with the addition of 1.0% hooked end and 0.5% crimped fibers improving compressive strength. Excessive fiber content (1.0% crimped fiber) led to a reduction in strength. While steel fibers had a negligible effect on elastic modulus, they significantly mitigated creep deformation in the concrete matrix. Specifically, HPC containing 0.5% and 1.0% hooked end fibers showed 6% and 26% lower creep strain, respectively, compared to plain HPC under constant load for 91 days. Both instantaneous and creep recovery strains increased with steel fiber content. According to the findings, the fiber-reinforced sustainable HPCs produced in this study met high performance concrete standards, achieving compressive strengths of over 28 MPa at 3 days and 80 MPa at 90 days, with notably high dimensional stability.