Total and initial fracture energies of self-compacting lightweight concrete containing silica fume and nano-silica

•Fracture parameters of SCLC are obtained using both work of fracture and size effect methods.•The effects of substituting cement with nano-silica and silica fume on the fracture parameters of SCLC are studied.•The amount of cement replacement materials can affect the brittleness of SCLC specimens.•A power relation is proposed to predict the initial and total fracture energies.•Both the initial and total fracture energies enhanced as silica fume and nano-silica were used in SCLC mixes.•The SCLC mix incorporating 3% nano-silica and 10% silica fume had the best quality. In this research, the effect of varying cement substitution materials on the fracture behavior of self-compacting lightweight concrete (SCLC) was experimented with using work of fracture method (WFM) and size effect methods (SEM). Portland cement was replaced with 0 % and 10 % silica fume (SF) as well as 0 %, 1 %, 3 % and 5 % nano-silica (NS) in varying proportions with water-to-cement (W/C) ratios of 0.35 and 0.45. The results demonstrated that using SF and NS in SCLC mixes enhanced the viscosity and decreased the fluidity of fresh concrete. Overall, 240 notched beams with sixteen mix designs were tested using the three-point bending test to determine and analyze the fracture parameters. The results showed that replacing 10 % of cement weight with SF enhanced the total and initial fracture energy by up to 21 % and 11 %, respectively,in a W/C ratio 0.45. The SCLC incorporating 3 % NS and 10 % SF had the best quality. This mixture increased the initial fracture energy, total fracture energy, fracture toughness, compressive strength and splitting tensile strength of SCLC by about 32, 38, 24, 36 and 17 % compared to the control mix.