Investigation of the effect of steel fiber type and content on the bending behavior of lightweight reinforced concrete beams

In this study, the effects of steel fiber aspect ratio (fiber length/fiber diameter) and steel fiber content on the behavior of structural lightweight reinforced concrete beams, produced using reference lightweight concrete class LC25/28, under bending were investigated. Considering the reference concrete mix, specimens with a total of 13 different concrete mixes, including the reference group, were produced by using steel fibers with 3 different aspect ratios (55, 65 and 80) in four different steel fiber contents (15 kg/m3, 30 kg/m3, 45 kg/m3 and 60 kg/m3). Moment capacity, load-deflection curve, energy consumption capacity and moment-curvature relationship were determined on reinforced concrete beam specimens. Flexural strength, fracture energy, fracture toughness, load-deflection and load-CMOD (crack mouth opening displacement) curves and characteristic length values were also determined by flexural test on the prismatic beam samples. In order to obtain the other mechanical properties, compression and splitting tensile tests were carried out on standart cylinder specimens. Stress-strain curves, compressive strength, modulus of elasticity, compressive toughness, compressive toughness index and ductility factor of the samples were determined by axial compression tests. It was determined that steel fibers improved the yield load, load carrring and energy consumption capacites of ligtweight reinforced concrete beams. It is also observed that there were increases in moment capacity and flexural rigidity. Splitting and flexural strengths, fracture energy and toughness of concrete specimenes were increased by using steel fibers. On the other hand, increases in compressive strength in comparision to splitting and flexural strengths were obtained lower.