Mechanical properties and chloride permeability of green concrete mixed with fly ash and coal gangue

A vast amount of CO2 is released in the cement production and its application. Numerous researches are paying close attention to replacing cement with any natural and/or recyclable components to reduce the waste emissions and protect the environment. Fly ash (FA) and coal gangue (CG), as supplementary cementitious materials, can be used as a replacement of cement in order to prepare green concrete. In this research, an indoor experimental study was conducted to explore the mechanical properties and chloride permeability of concrete incorporating fly ash and coal gangue and to evaluate their application possibility. The cement replacement level was set at 10%, 20%, 30%. Each replacement level consisted of 7 different mass ratios of fly ash to coal gangue including 100/0, 80/20, 60/40, 50/50, 40/60, 20/80 and 0/100. Furthermore, the effect of different fineness (200 mesh, 325 mesh, 500 mesh, 1250 mesh, 2000 mesh) of coal gangue on the mechanical properties, frost resistance and chloride ion penetration resistance of concrete was studied. Results of this study indicated that the optimal replacement level of 20% for green concrete with the mass ratio of fly ash to coal gangue at 40/60 resulted in 4.5% and 5% improvement in mechanical performance and chloride penetration resistance, respectively. Also, 2000 mesh was recommended as the optimal fineness of coal gangue in comprehensive consideration of mechanical performance, chloride penetration and frost resistance.