Influence of Steel Fiber Distribution on the Mechanical Performance of SFRC

Abstract This study investigated the flexural behavior of steel fiber-reinforced concrete (SFRC) with a nonuniform fiber distribution using a layered casting approach. Specimens composed of a fiber-reinforced bottom layer and a conventional concrete top layer (layered SFRC, LSFRC) were produced and compared with conventional SFRC and plain concrete. Three fiber aspect ratios (44, 67, and 80) and two fiber volume fractions (1% and 2%) were evaluated. The results demonstrated that LSFRC improved the flexural performance compared with conventional SFRC. The flexural strength increased by up to 90% relative to plain concrete and by up to 49% compared with SFRC containing the same fiber volume fraction. The toughness showed more pronounced gains, reaching values approximately five times higher than those of plain concrete. The best overall performance was obtained with the fiber volume fraction of 1% and the aspect ratio of 67, which provided the most balanced combination of strength and toughness. Increasing the fiber volume fraction to 2% did not produce proportional performance improvements, indicating reduced efficiency at higher fiber dosages. In addition, the reference SFRC mixtures were characterized in terms of compressive strength, elastic modulus, water absorption, and apparent density. The incorporation of fibers did not adversely affect these properties. Overall, the results indicate that strategically concentrating fibers within the tensile zone is an effective approach to optimize flexural performance while reducing fiber consumption.