Mechanical properties and failure mechanism of fiber-reinforced concrete materials: Effects of fiber type and content

This research examines the influence of fiber type and content on the mechanical properties and failure mechanisms of fiber-reinforced concrete. It focuses on steel fibers (SF), carbon fibers (CF), and basalt fibers (BF), aiming to optimize concrete performance for engineering applications. The results show that compared with plain concrete (PC), fibers to some extent affect the compactness of the specimen, which promotes the more obvious initial pore compression characteristics. As fiber content increases, the failure mode shifts from brittle to plastic, with transition points at 0.5 % for steel fiber concrete (SFC), 1.0 % for basalt fiber concrete (BFC), and 1.0 % for carbon fiber concrete (CFC). The fibers have a certain effect on the density, compressive strength and elastic modulus of the concrete. In the respective mix proportion systems, the optimal content of SF is 2.0 %, CF is 1.0 %, and BF is 0.5 %. The fiber content can improve the compactness and load-bearing capacity of concrete to a certain extent. However, excessive content will induce the "saturation" of concrete to fibers, leading to the phenomenon of fiber "agglomeration". This will further affect the physical properties, strength characteristics, and deformation characteristics of concrete. Notably, a positive correlation exists among these three aspects, with the correlation coefficient being greater than 0.9 for SFC, and around 0.50 for CFC and BFC. The fiber 'bridging effect' and 'weak interface effect' significantly influence mechanical properties, with SFC specimens showing notably less damage compared to CFC and BFC. Additionally, increased fiber content improves post- failure integrity, reducing crack width and number, and enhancing concrete toughness.