Evaluation of Potential Factors Affecting Steel Slag Carbonation

Abstract

Steel slag is a solid waste product generated during the carbonation stage of steelmaking. It has high levels of heavy metals and substantial amounts of free calcium and magnesium oxide, making it unsuitable for use as a cement material. Furthermore, the disposal of steel slag in landfills requires many resources and can seriously contaminate the surrounding environment. One method of reducing its negative environmental impact is carbonation, which involves reacting steel slag with carbon dioxide to form stable minerals. However, many parameters influence the carbonation efficiency of steelmaking slag, including temperature, time, particle size, pressure, CO2 concentration, liquid-to-solid ratio, moisture content, humidity, additives, etc. To this end, this paper comprehensively reviews the most important steel slag carbonation-influencing factors. Moreover, it compares the characteristics from two perspectives based on their causes and effects on carbonation. Finally, this article reviews earlier studies to identify the factors that affect steel slag carbonation and the potential of carbonated steel slag as a sustainable construction material. Based on previous research, it systematically examines all the elements for future work that need to be improved.

A Review on the Carbonation of Steel Slag: Properties, Mechanism, and Application

“…Direct dry carbonation is similar to natural weathering, where f-CaO, f-MgO, Ca(OH)2, Mg(OH)2, C2S, and C3S in steel slag directly react with CO2, as shown in the following chemical Formulas (1)-( 6) [57][58][59]:…”

“…Initially, CaO and MgO hydrate to form Ca(OH)2 and Mg(OH)2; C3S and β-C2S hydrate to form C-S-H and Ca(OH)2. These phases further react with CO2 to produce CaCO3, MgCO3 and silica-rich C-S-H gel [57,59]. On the other hand, CO2 dissolves in water in the form of H2CO3 to react with C3S, and β-C2S and γ-C2S.…”

“…The components are involved in the reaction between CO 2 and hydration products of mineral phases in steel slag, including the hydration of free-CaO, free-MgO, C 3 S, and β-C 2 S. Initially, CaO and MgO hydrate to form Ca(OH) 2 and Mg(OH) 2 ; C 3 S and β-C 2 S hydrate to form C-S-H and Ca(OH) 2 . These phases further react with CO 2 to produce CaCO 3 , MgCO 3 and silica-rich C-S-H gel [57,59]. On the other hand, CO 2 dissolves in water in the form of Compared with direct dry carbonation, direct wet carbonation is a complex threephase reaction process, but it can achieve high CO2 sequestration at room temperature under atmospheric pressure.…”