Effects of steel fiber length and coarse aggregate maximum size on mechanical properties of steel fiber reinforced concrete

•Steel fiber length has greater effects on mechanical properties of SFRC than coarse aggregate maximum size.•Rational range of the ratio of steel fiber length to coarse aggregate maximum size was proposed.•SFRC with large size coarse aggregate and long steel fiber shows favorable performances.•Large size coarse aggregate is matched well with long steel fiber. This study investigated the effects of steel fiber length and coarse aggregate maximum size on mechanical properties of steel fiber reinforced concrete (SFRC). The experimental results show that the mixture slump, splitting tensile strength, flexural strength, initial flexural toughness ratio, flexural toughness ratio, fracture energy and unstable fracture toughness of SFRC increase as steel fiber length increases. The compressive strength and initial fracture toughness are barely influenced by steel fiber length. With the increase of coarse aggregate maximum size, (a) the mixture slump increases, (b) compressive strength shows slight variations, (c) splitting tensile strength, flexural strength, fracture energy and unstable fracture toughness increase first and then decrease, (d) there are none indicative variations for initial flexural toughness ratio, flexural toughness ratio and initial fracture toughness. The rational range of the ratio of steel fiber length to coarse aggregate maximum size is 1.25–3 for the considerable strengthening effect of steel fiber on splitting tensile strength and flexural performances of concrete and 1–4 for that on fracture characteristics respectively.