Shear strength of eco-friendly self-compacting concrete beams containing ground granulated blast furnace slag and fly ash as cement replacement

Abstract

It is becoming essential to find solutions to preserve the environment from emissions related to cement manufacture. One of the most effective solutions and techniques is using supplementary cementitious materials (SCMs) as cement substitutes to produce eco-friendly concrete. This experimental work primarily aimed to investigate the impact of ground granulated blast furnace slag (GGBFS) and fly ash (FA) as cement substitutes on the shear behavior of SCC beams. Six SCC mixtures with binary and ternary binders based on cement, FA, and GGBFS were manufactured. Twelve SCC beams (two beams for each mixture) with and without shear reinforcement were cast and tested under simply supported four-point loading conditions. Test variables were different substitute levels of GGBFS and FA (0 %, 25 %, and 50 %) of the total weight of cement and shear reinforcement ratio. The findings indicated that the addition of GGBFS and FA had a negative impact on the mechanical characteristics of SCC. The stiffness, ultimate shear strength, and toughness of SCC beams decrease with the increase of GGBFS and FA contents. The ultimate shear strength of tested beams without stirrups comprising GGBFS and FA up to 50 % was reduced by about 12.1 % and 19.3 %, respectively. The ultimate shear strength, shear ductility, and stiffness of tested beams comprising up to 50 % GGBFS were reduced by about 10.5 %, 36.4 %, and 9.1 %, respectively. Based on the experimental results, from both an environmental and engineering perspective, a combination of ternary binders based on 50 % cement, 25 % FA and 25 % GGBFS can be considered the optimum substitute ratios that can be used on the SCC mixture. Whereas it contains a high level of SCMs causing a minimal impact on shear strength with the improvement of the ductility of SCC beam. Lastly, the experimental ultimate shear strength of test specimens was compared with those predicted from different international design codes.