The risk of global warming is increasing every year. Efforts to solve this global warming are underway around the world. Among several measures, the most recent recommendation was that global carbon neutrality (Zero carbon, Net zero) should be achieved until 2050. Based on this, countries around the world declared carbon neutrality by 2050. One of the main causes of global warming is carbon dioxide (CO2) emitted during cement manufacturing. Currently, some research is being conducted to reduce cement usage by utilizing industrial by-products. The most representative industrial by-product is blast furnace slag (BFS). Concrete using BFS has advantages such as increased long-term strength and improved durability. However, there are two main problems: First, concrete using BFS has low initial strength due to the presence of an impervious film on the BFS surface. Second, carbonation resistance is low because calcium hydroxide (Ca(OH)2) is consumed during the hydration process of BFS. Some research has been done to solve these problems. Among them, research using alkaline activators is representative. Alkaline activators are effective in solving the problem, but they are expensive and their high pH concentration makes them difficult to use in the field.
Therefore, in this study, an alkaline aqueous solution obtained by electrolysis is used as a mixing water to complement the existing problems of BFS and alkali activator and to improve the initial hydration reaction and carbonation resistance of BFS. Because an alkaline aqueous solution of approximately pH 12.0 to 12.5 is required to remove the surface impermeable film of BFS, it was manufactured using potassium carbonate as an electrolyte. Validation experiments are divided into strength, hydration and durability properties. Hydration characteristics were confirmed through SEM analysis, and durability characteristics were confirmed through accelerated carbonation tests and rapid chlorine ion penetration resistance tests. Additionally, MIP analysis was also performed to confirm void changes.
As a result, it was confirmed that BFS-substituted concrete using electrolyzed alkaline water as mixing water improved the initial hydration reactivity and initial strength. Additionally, it was confirmed that the amount of hydrate products inside the concrete increased. This is believable because the film of the BFS particles was removed with an alkaline aqueous solution. It was confirmed that neutralization resistance and chlorine ion penetration resistance also increased. It was considered as a result that hydrate products fulfill the pores in concrete. In addition, as a result of MIP analysis, it was confirmed that the pores of the cured material using alkaline water through electrolysis were filled more tightly.
Therefore, the aqueous alkaline solution obtained by electrolysis is believed to be effective in improving the initial hydration reactivity and durability through destruction of the surface impermeable film of BFS.