## 1 Introduction  
Steel slag is a prominent by-product generated during the smelting process in the iron and steel industry, constituting approximately 8-15% of the total crude steel production [1, 2, 3]. In 2021, global crude steel production reached around 1.952 billion tons, resulting in an annual emission of steel slag exceeding 250 million tons [4]. Among these figures, China's crude steel production accounted for about 1.03 billion tons with a corresponding output of over 120 million tons of steel slag [5]. However, steel slag possesses drawbacks such as high free CaO content and low hydration activity [6], leading to its combined utilization rate remaining below 30% [7]. Consequently, it is primarily stockpiled or landfilled, posing significant environmental pollution concerns. Therefore, there is an urgent need to develop an efficient and environmentally friendly approach to the disposal of steel slag. Meanwhile, the steel production process is accompanied by a substantial amount of carbon emissions. The carbon emissions of China's iron and steel sector account for approximately 15% of the national total [8]. Carbon Capture, Utilization and Storage (CCUS) is widely regarded as an optimal approach to achieve significant carbon emission reduction in the iron and steel industry [9, 10]. By harnessing CO\({}_{2}\), it becomes possible to convert the high calcium content present in steel slag into highly stable CaCO\({}_{3}\), thereby facilitating long-term carbon sequestration [11]. The CO\({}_{2}\) carbonation of steel slag has been acknowledged as the most favorable method for disposing of this by-product. Steel slag can be classified into basic oxygen furnace slag (BOFS), electrical arc furnace slag (EAFS), argon oxygen decarburization slag (AODS), and ladle-refining slag (LFS) based on the production process [4; 10]. Among these, LFS is a by-product generated during secondary or alkaline steelmaking [12], and it exhibits the highest calcium content among all types of slags [13]. The cooling process of the LFS results in the generation of a substantial quantity of the self-powdered \(\gamma\)-Ca\({}_{2}\)SiO\({}_{4}\) (\(\gamma\)-C\({}_{2}\)S) material phase, thereby conferring a powdery nature upon the LFS. The \(\gamma\)-C\({}_{2}\)S enables a rapid reaction with CO\({}_{2}\) to form calcium carbonates (CaCO\({}_{3}\)) and calcium silicate hydrates (C-S-H) [14; 15]. Consequently, LFS holds great potential for application in CCUS technology. The carbonation process of steel slag building materials typically involves mixing water with steel slag powder to form cubic blocks, which are then subjected to a direct gas-solid reaction by passing CO\({}_{2}\) gas through a closed stainless steel reactor [16; 17]. Some researchers have also utilized liquid-solid reactions [18]. During the reaction between CO\({}_{2}\) and steel slag, CO\({}_{3}\)[2]- formed from dissolved CO\({}_{2}\) reacts with Ca\({}^{2+}\) precipitated from the slag to produce stable CaCO\({}_{3}\) that provides high mechanical strength and permanently fixes CO\({}_{2}\) in the material [6]. Although the theoretical carbon fixation rate of steel slag ranges between 25% and 50%, various factors during carbonation limit its actual rate to about 15% [19]. Each ton of cement produced will emit 0.94 tons of CO\({}_{2}\)[20], so when carbonation of steel slag is applied in cementitious materials or aggregates to replace cement, the reduction in cement production and the amount of CO\({}_{2}\) absorbed by the steel slag makes it possible to achieve a carbon reduction of approximately 1.09 t of CO\({}_{2}\) for each ton of steel slag. This would be expected to achieve the carbon-negative production of building materials. Gas-solid carbonation is mainly restricted by reaction kinetics and CO\({}_{2}\) diffusion [4]; hence, researchers strive to study different conditions in this process for improved efficiency.