Effect of micro steel fibers volume fraction on behavior of high-strength self-compacting concrete

Self-Compacting Concrete (SCC) is an innovative construction material that flows and compacts under its own weight, making it ideal for complex structures due to its high workability. Micro steel fibers, smaller in size than conventional fibers, have recently been adopted in both research and industry due to their limited effect on workability, which facilitates casting and construction process, alongside their promising contributions to enhancing the mechanical performance of concrete. The mechanical, rheological, and electrical properties of micro steel fiber-reinforced high-strength SCC members were investigated in this study. The testing program included prismatic specimens (100 x 100 x 500 mm3), cubic specimens (150 x 150 x 150 mm3), and cylindrical specimens (100 mm x 200 mm). The micro steel fiber contents considered were 0.0 %, 0.35 %, 0.70 %, and 1.05 % by volume. Test results revealed that the inclusion of micro steel fibers reduced workability, particularly above a 0.70 % fiber content, and resulted in maximum enhancement rates of 13.3 % in compressive strength, 52.4 % in splitting tensile strength, and 13.2 % in flexural strength compared to fiber-free specimens. The toughness index (T150) was enhanced by up to 40 % at higher fiber volumes. These findings highlight the balance between workability and mechanical improvement provided by micro steel fibers. Bulk electrical resistivity exhibited a clear decreasing trend with increasing fiber content.