Experimental study on full-volume slag alkali-activated mortars: Air-cooled blast furnace slag versus machine-made sand as fine aggregates

Highlights: • ACBFS can be high-volume used to replace fine aggregate in alkali-activated mortar. • Use ACBFS as machine-made sand replacement to improve mechanical properties of FSAM. • FSAM mixed with ACBFS has good microstructure and durability. As the industrial waste from blast furnace ironmaking, air-cooled blast furnace slag (ACBFS) puts a lot of pressure on the environment. It is becoming more and more urgent to deal with the increasing ACBFS. In this study, the concept of "full-volume slag alkali-activated mortars (FSAM)" is proposed using ground granulated water-cooled blast furnace slag (GGBS) as aluminosilicate material and ACBFS to replace machine-made sand, aiming to solve the current situation of increasing scarcity of natural resources. The characteristics of ACBFS are investigated, and its stability and heavy metal leaching all meet the requirements as a building material. The results show that the flowability and mechanical properties of FSAM are significantly enhanced with the substitution rate of ACBFS increases. Meanwhile, the incorporation of ACBFS is also beneficial to improve the compactness of the microstructure of the mortar, thereby improving the impermeability (Water, ion and gas) of FSAM. In addition, the specimen mixed with ACBFS showed good high temperature resistance due to the porous feature of the aggregate. Furthermore, using a small amount of limestone powder to replace GGBS can slightly improve the performance of FSAM. Therefore, ACBFS is recommended to be used in FSAM, which meets safety, cost and environmental benefits.