The effects of volume fraction and aspect ratio of steel fiber on fracture parameters of steel fiber reinforced lightweight concretes

This study involves the experimental investigation of the effects of steel fiber volume fraction and aspect ratio on the fracture parameters of steel fiber reinforced lightweight concrete (SFLWC). Specimens were produced by adding steel fibers with aspect ratios (steel fiber length/steel fiber diameter) of 55, 65 and 80 at fiber contents of 0, 15 kg/m³, 30 kg/m³, 45 kg/m³ and 60 kg/m³ to lightweight concrete produced using pumice aggregate. The reference lightweight concrete strength class was taken as LC25/28. Compressive, splitting tensile and flexural tensile tests were performed on specimens. Load-crack mouth opening displacement (CMOD) curves, fracture energies, characteristic lengths and fracture toughness were also determined by flexural tests. The stresses transferred to the steel fibers after the first crack were carried by the steel fibers, preventing sudden failure and this behavior continued until the steel fibers were pulled out from the matrix. Accordingly, the steel fibers improved the behavior of the concrete after the peak load and continued to deform under decreasing load. With increasing amount of strain, the toughness or energy absorption capacity of the semi-brittle concrete increased. Based on the test results obtained, significant increases in fracture energy, splitting and flexural tensile strengths were obtained by increasing the amount of steel fiber.