Impact of using different amounts of polyolefin macro fibers on fracture behavior, size effect, and mechanical properties of self-compacting lightweight concrete

•Effect of polyolefin fibers on fracture properties of SCLC has been assessed.•Fiber contents have negligible effects on mechanical properties of SCLC.•Fracture energy and toughness of the mixes showed almost no size dependency.•The so-called universal size-shape effect law was adopted successfully. In this paper, the effect of polyolefin macro fibers on fracture, fresh and hardened state properties of self-compacting lightweight concrete (SCLC) has been assessed. To do so, four SCLC mixes have been cast such that the solid contents and water to binder ratio have been kept constant while the volume fraction of fiber contents varied from 0.0% to 0.5% by concrete volume. Moreover, to evaluate the effect of size on fracture parameters and nominal strength of the beams, three different sizes of specimens were considered such that they have been kept geometrically similar. The experimental results showed that the fiber contents have negligible effects on mechanical properties of SCLC. However, the post peak behavior of the specimen was affected by the amount of fiber contents. The so-called universal size-shape effect law was adopted successfully to indicate the effects regarding the size of the specimens on their nominal strength. Besides, the fracture energy and fracture toughness of the mixes showed almost no size dependency, especially for characteristic dimensions higher than 100 mm.