Opposite effects of ground granulated blast-furnace slag and silica fume on the fracture behavior of self-compacting lightweight concrete

In this study, an experimental investigation is presented on the fracture behavior of self-compacting lightweight concrete (SCLC) including different contents of cement replacement materials. Portland cement was substituted with silica fume (SF) and ground granulated blast-furnace slag (GGBFS) in different proportions with and without magnetic water (MW) for this purpose. The results displayed that cement replacement materials in SCLC decreased the rheology of concrete. At hardened state, fracture behavior and mechanical properties were investigated at the age of 28 days. For determination of SCLC fracture parameters three-point bending tests were carried out on 120 notched beams. The test results showed that when the SF content increased from 0 to 5 and 10% of the cement weight, the initial fracture energy improved by 19 and 24%, and the fracture toughness increased by 14 and 18%, respectively. However, when the GGBFS content increased from 0 to 10 and 20%, the initial fracture energy decreases by 11 and 19%, and fracture toughness decreased by 7 and 13%, respectively. Moreover, it was observed that the SCLC incorporating 10% of SF and MW was the best mix design. This mix improved the initial fracture energy, fracture toughness, tensile strength and compressive strength of SCLC up to 31%, 22%, 25% and 34%, respectively. (C) 2019 Elsevier Ltd. All rights reserved.