Study on preparation and CO2 sequestration mechanism of high-strength carbonated Ladle refining slag binder

Study on preparation and CO2 sequestration mechanism of high-strength carbonated Ladle refining slag binder | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Study on preparation and CO 2 sequestration mechanism of high-strength carbonated Ladle refining slag binder Ping Chen, ShenQiu Lin, WeiHeng Xiang, Cheng Hu, FangBin Li, Yu Ding This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3621729/v1 This work is licensed under a CC BY 4.0 License Status: Under Revision Version 1 posted 6 You are reading this latest preprint version Abstract Ladle refining slag (LFS), classified as solid waste, presents an imminent need for comprehensive utilization. Notably, LFS contains a substantial amount of γ-Ca 2 SiO 4 (γ-C 2 S) with remarkable carbonation potential, making it an ideal candidate for the production of carbonated cement through Carbon Capture and Storage (CCS) technology. This study delves into the carbonation reaction of the cast and molded lump LFS within a CO 2 pressure vessel. It systematically examines the influence of water-solid ratio and water content on the initial properties of specimens. Furthermore, the investigation encompasses the impact of temperature, reaction time, and CO 2 pressure on carbonation processes and resultant products, contributing to the formulation of a carbonation reaction and mass-transfer mechanism. The research reveals pivotal findings: lower water-solid ratios lead to denser specimens with higher strength, and an optimal 7% water content facilitates effective cementation and reactant dissolution. The controlled growth of densely layered calcite at 20°C yields impressive strengths of up to 120.5MPa, while elevated temperatures, such as 60°C, encourage the growth of smaller calcium carbonate crystals, resulting in a favorable carbon sequestration rate of 19.72%. Extending the carbonation time enhances the conversion rate of γ-C 2 S to calcium carbonate. Intriguingly, CO 2 pressure exerts minimal influence on the specimens. The research elucidates the five-step carbonation process and its underlying diffusion mechanism. In essence, this study harnesses CCS technology to offer a high-value solution for addressing LFS disposal challenges. Carbon capture Ladle refining slag Binder Carbonation reaction High strength Dicalcium silicate mechanism Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Introduction In recent years, global CO 2 emissions have surged due to rapid industrialization, surpassing 3 billion tons annually (Li et al. 2022 ), resulting in climate warming and rising sea levels (Fu et al. 2022 ). Among the major contributors to carbon emissions, the construction industry stands out, with a staggering 9.95 Gt/y of CO 2 emissions (Hanifa et al. 2022 ). To promote sustainable and low-carbon practices in the building materials sector, researchers worldwide have developed various technologies to reduce carbon emissions associated with cement-based materials. Employing carbon capture and storage (CCS) technology stands as a promising method for mitigating the greenhouse effect (Fu et al. 2022 ; Liu et al. 2021 ; Pan et al. 2012 ). Meanwhile, steel slag, a predominant by-product of iron and steel production, continues to accumulate, exceeding 250 million tons annually on a global scale (Zhang et al. 2023 ). In China alone, steel slag production exceeds 120 million tons (Gao et al. 2023 ). Unfortunately, steel slag faces significant challenges due to its high free CaO content, poor abrasiveness, and low hydration activity (Song et al. 2021 ). As a result, its utilization rate remains below 30% (Rui et al. 2022), with most of it ending up in landfills (Najm et al. 2020 ), posing environmental risks due to leaching alkaline ions and heavy metal ions. Notably, steel slag can be categorized into different types based on production processes, with the Ladle Refining Slag (LFS) being a by-product of secondary or alkaline steelmaking (Espinosa et al. 2023 ). LFS primarily comprises γ-Ca 2 SiO 4 (γ-C 2 S), CaO, MgO, and other minerals (Xu et al. 2022; Zhang et al. 2023 ). The extremely low hydration activity of γ-C 2 S significantly limits LFS utilization. Recent findings, however, have uncovered the carbonation potential of silicate minerals, particularly γ-C 2 S (Mu et al. 2019 ), suggesting the possibility of efficiently converting LFS using CCS technology to create carbonated steel slag-based binders with exceptional performance. While numerous studies have explored the carbonation behavior of steel slag, most have focused on Basic Oxygen Furnace Slag (BOFS). For instance, BOFS specimens have demonstrated strengths of up to 80 MPa in just 2 h (Ghouleh et al. 2015 ). Current LFS studies are very limited and mostly focused on CO 2 curing of heavy metals (Xu et al. 2022). However, there is untapped potential in LFS carbonation, and understanding the influencing factors of the preparation process is crucial. Researchers have predominantly focused on variables like temperature, carbonation time, and CO 2 pressure (Luo et al. 2021 ; Zhong et al. 2021 ), overlooking the impact of specimen water content, which can significantly influence carbonation product formation. Additionally, most studies have employed pressed shaping methods (Chang et al. 2021 ; Ghouleh et al. 2015 ; Mahoutian et al. 2014 ; Zhang et al. 2022 ; Zhong et al. 2021 ), which have been successful in achieving impressive strengths. Leaving gaps in our understanding of pouring and molding, a common engineering practice. This study aims to develop an energy-efficient, low-carbon, high-strength carbonated LFS binder using pouring and molding techniques. It systematically investigates water-solid ratio and water content, carbonation temperature, carbonation time, and CO 2 pressure's effects on carbonated LFS performance to derive an optimal preparation process. The study delves into the influence of water on CO 2 diffusion, observes the morphology of carbonation products at various temperatures, and derives a theoretical diffusion model for the carbonation process of steel slag. These findings pave the way for the utilization of carbonated steel slag in bricks, prefabricated components, cementitious materials, and more, addressing steel slag stockpiling issues and enabling low-carbon or even carbon-negative production in the building materials industry through CCS technology. Materials and methods Raw material In this paper, Ladle Refining Slag (LFS) utilized originated from Guangxi Beibu Gulf New Material Co., Ltd. The chemical composition of LFS is detailed in Table 1 . The K 2 SO 4 employed is a chemically pure reagent with a purity of 99.95% (AR), while the CO 2 utilized is of industrial grade, boasting a purity level of 99%. The LFS was initially subjected to ball milling for 1 hour, followed by screening through a 100-mesh sieve. In Fig. 1 (a), the primary particle size distribution of LFS micro powders, following milling and sieving, ranged from 0.2 to 20 µm, with an average particle size distribution D50 of 2.77 µm. As shown in Fig. 1 (b), the primary physical phase compositions of LFS included γ-Ca 2 SiO 4 (γ-C 2 S), Ca 2 Mg(Si 2 O 7 ), and Mg 2 SiO 6 . It was shown that Mg + can also participate in the carbonation reaction (Baciocchi et al. 2015 ; Polettini et al. 2016 ; Yi et al. 2021 ). Considering the favorable carbonation activity of LFS, this suggests that LFS can be utilized to produce carbonated steel slag-based binders with outstanding mechanical properties through carbonation reactions. Table 1 Chemical compositions of LFS(wt%). Oxides CaO SiO 2 Cr 2 O 3 MgO TiO 2 Fe 2 O 3 others LFS 69.20 22.56 2.46 2.13 1.81 1.49 0.35 Preparation process and reaction equipment LFS micro powder and water were combined in a net slurry mixer in accordance with water-solid ratios of 0.25, 0.3, and 0.35. The mixture was blended for 4 minutes, after which it was cast into 20×20×20mm cube molds for shaping. After undergoing 24 hours of natural curing at ambient temperature, the molds were removed and the specimens were subsequently dried in the air at room temperature (25°C) for varying durations. This step was performed to attain a final water content ranging from 0–10% prior to carbonation, which was determined using Eq. (1). Subsequently, the specimens were placed in a carbonation kettle under a vacuum pressure of -0.8MPa, at temperatures ranging from 20–80°C, and a CO 2 pressure of 0.1-0.4MPa for a 24h carbonation reaction. Following the completion of the reaction, microstructural and property tests were conducted. w %=( M 1 - M 2 )/ M 2 ×100% (1) The water content of the specimen, denoted as w %, is controlled within an error range of ± 0.1%. M 1 represents the weight of the wet base specimen, which can be determined by weighing the carbonated sample. M 2 corresponds to the weight of the dry base specimen, obtained by completely drying a parallel set of specimens from the same group. The weighing process ensures that errors are limited to 0.1%; otherwise, retesting is required. The carbonation equipment used in the test mainly consists of a carbonation reactor, water bath, vacuum pump, and industrial pure CO 2 cylinder, see Fig. 2 . Saturated K 2 SO 4 solution was placed at the bottom of the reactor to maintain high humidity inside the kettle, and the humidity could be maintained above 90% at 20–80℃. With the bracket and the metal, the mesh would be carbonated samples above the saturated solution surface to ensure that the CO 2 and water are fully in contact with the surface of the specimen. Test methods The compressive strength of the specimens was tested in accordance with the standard GB/T 17671 − 2021. The X-ray diffraction pattern test was conducted using an X`Pert PRO X-ray diffractometer from PANalytical, the Netherlands, equipped with a Cu Kα (λ = 1.5406Å) X-ray source and a scanning range of 2θ from 5 to 80°. Microscopic morphology analysis was performed using a Zeiss model S-4800 scanning electron microscope with an accelerating voltage of 5 kV. Temperature changes during carbonation were recorded by inserting a temperature probe from a continuous pyrometer (T20BL-EX) into the center of the specimen after formation. The specimen was then placed in the carbonation kettle at room temperature, and the temperature change curve over time was measured. The carbon sequestration rate of the specimen was analyzed using thermogravimetry (TGA) according to the calculations shown in Eq. ( 2 ) and Eq. ( 3 ) (Li et al. 2021 ). The testing temperature ranged from 25°C to 1000°C, with a heating rate of 5°C/min, in a nitrogen atmosphere. Where CO 2 ( wt .%) denotes the rate of CO 2 loss, ∆m CO2 denotes the rate of mass loss during the decomposition of calcium carbonate to produce CO 2 at elevated temperatures of the specimen, m 105°C denotes the weight of the specimen after drying, CO 2 uptake (wt.%) denotes the rate of carbon sequestration, and CO 2carbonated (wt.%) denotes the rate of CO 2 loss after carbonation of the specimen. CO 2initial (wt.%) indicates the CO 2 loss rate of the uncarbonated specimen. Results and discussion water-solid ratio and water content In this study, we examined the characteristics of LFS specimens with varying water-solids ratios and water contents, which were carbonated for 24 hours at room temperature (25°C) and a CO 2 pressure of 0.4 MPa. The resulting compressive strengths for each specimen are depicted in Fig. 3 . Notably, the compressive strength of the specimens exhibited a decreasing trend as the water-solid ratio increased. This was attributed to the fact that specimens with lower water-solid ratios tend to be denser and less porous, leading to an optimal compressive strength of 113.5MPa observed at a water-solid ratio of 0.25 and a water content of 7%. However, a higher water-solid ratio offers improved pourability and moldability, prompting the selection of a water-solid ratio of 0.3 for subsequent tests. As shown in Fig. 4 , the compressive strength and carbon sequestration rate of the specimens displayed an initial increase followed by a decline with increasing water content. This phenomenon is attributed to the higher water content providing an increased supply of water for the carbonation reaction, resulting in a greater degree of carbonation for γ-C 2 S and other active components. Consequently, more calcium carbonate is generated, contributing to enhanced compressive strength and carbon sequestration rates. This is supported by the intensification of calcium carbonate diffraction peaks and the weakening of γ-C 2 S diffraction peaks in Fig. 5 . The peak performance was achieved when the water content reached 7%, as at this point, the appropriate water content facilitated bridging between particles, bonding them together without excessively affecting carbonation on the particle surfaces. This allowed for deep penetration of carbonation into the specimen's interior, ensuring effective dissolution of Ca 2+ and CO 2 . Consequently, calcium carbonate crystals could grow successively, yielding specimens with a compressive strength of up to 90.08MPa and a carbon sequestration rate of 18.09%. However, further increases in water content led to a sharp decline in performance. Specimens with water content of 8% and above exhibited compressive strengths of only about 5MPa, with XRD analysis revealing pronounced γ-C 2 S diffraction peaks. This decline is attributed to the formation of a "water film" on the specimen and particle surfaces due to high water content, hindering CO 2 diffusion into the interior. Excess water also clogged the steel slag mass's pores, impeding CO 2 diffusion further. In conclusion, water content plays a critical role in the characteristics of carbonated specimens, primarily due to its role as a medium for Ca 2+ and CO 2 dissolution, which is crucial for CO 2 diffusion—a key determinant of the early carbonation rate (Zhong et al. 2021 ). Thus, the forming optimal process parameters for LFS were determined to be a water-solid ratio of 0.3 and a water content of 7%. Carbonation temperature In this study, we investigated the properties and microstructures of LFS specimens that were carbonated at varying temperatures for a duration of 24 hours, under a CO 2 pressure of 0.4 MPa. In Fig. 6 (a), it is evident that the compressive strength of carbonated LFS at 20°C reaches an impressive 120.5MPa. However, as the carbonation temperature increases, the compressive strength of the specimen gradually decreases. This phenomenon may be attributed to the elevated temperature affecting the stable growth of calcium carbonate crystals. Research has indicated that laboratory-synthesized calcium carbonate can undergo interconversion between calcite, aragonite, and spherulite at specific temperatures (Wray et al. 1957). Higher temperatures reduce the solubility of CO 2 , and the increased internal temperature leads to faster evaporation of free water, resulting in limited leaching of calcium ions and reduced CO 2 solubilization (Humbert et al. 2019 ; Luo et al. 2021 ). These factors contribute to the decline in strength. Interestingly, the carbon sequestration rate exhibited an initial increase followed by a decrease with increasing temperature, mirroring the pattern of calcium carbonate peaks observed in the XRD pattern in Fig. 6 (b). The initial increase is likely due to the higher temperature leading to faster dissolution and mass transfer of substances, resulting in a deeper carbonation depth at the microscopic level and an increased carbon sequestration rate. For instance, the sample carbonated at 60°C exhibited the highest carbon sequestration rate of 19.72%, whereas at 80°C, this rate dropped to 15.02%. The decline in the carbon sequestration rate at higher temperatures can be attributed to several factors. Firstly, the elevated temperature causes excessive water loss within the specimen, disrupting the optimal water content required before carbonation. Secondly, the high temperature leads to an increased generation of water vapor at the bottom of the equipment, causing water to adhere to the specimen's surface. This, in turn, hinders mass transfer and the carbonation reaction. Figure 7 illustrates how the morphology of carbonated LFS becomes increasingly irregular with rising temperature. Smaller calcium carbonate crystals are observed, and the pores become more porous as the temperature increases. This irregular morphology may explain the decrease in compressive strength observed at higher temperatures. Specimens carbonated at 20°C exhibit slower growth of calcium carbonate crystals due to the lower temperature environment. This results in better densification of the matrix between the powder particles, yielding dense, massive, layered calcite (Fig. 7 (a)), which explains the high compressive strength. In contrast, specimens carbonated at 40°C exhibit various morphologies of calcite and aragonite crystals, such as shells, rods, flakes, blocks, and petals (Fig. 7 (b)). Those carbonated at 60°C still display blocky calcite and petaloid aragonite/vaterite (Fig. 7 (c)), while at 80°C, an irregular morphology is observed, with a profusion of fine crystals and gels encapsulating the particles (Fig. 7 (d)). This phenomenon can prevent effective carbonation within the particles, contributing to the reduced carbon sequestration rate at higher temperatures. In summary, the increase in temperature does not necessarily enhance the efficiency of the LFS carbonation reaction. While higher temperatures initially improve the reaction rate and generate many small carbonation product particles with a high carbon sequestration rate, they subsequently lead to the rapid encapsulation of particles by the carbonation product layer. Moreover, higher temperatures decrease the solubility of CO 2 , resulting in reduced carbonation efficiency. Carbonation time In this study, we examined the characteristics and degree of carbonation of LFS specimens that were carbonated for varying periods at room temperature (25°C) and CO 2 pressure of 0.4 MPa. As depicted in Fig. 8 (a), both the compressive strength and carbon sequestration rate of the specimens increased over time. This increase was particularly rapid in the initial 2 hours, reaching a compressive strength of 70.59MPa and a carbon sequestration rate of 16.27% after 2 hours of carbonation. Subsequently, at the 18-hour mark, the strength and carbon sequestration rate essentially reached saturation, with minimal further increases with extended carbonation time. Figure 8 (b) also reveals that the diffraction peaks of γ-C 2 S weakened as carbonation time increased, while the diffraction peaks of calcite became stronger. This observation suggests that γ-C 2 S gradually transformed into calcite crystals during the carbonation process, contributing to the rise in compressive strength and carbon sequestration rate. To visualize the depth of carbonation, a phenolphthalein indicator was applied to the middle section of the carbonated specimen. Uncarbonated alkaline steel slag remained red, while the carbonated area showed no color, as depicted in Fig. 9 (a). Carbonation progressed rapidly within the first hour, with CO 2 diffusion and dissolution reaching the interior within this timeframe or even earlier. By the 2-h mark, carbonation had penetrated deep into the interior, and specimens carbonated for 4 h or longer displayed no color change after phenolphthalein application. However, it's important to note that carbonation is a gradual process, involving the diffusion and dissolution of reactive substances and the nucleation and growth of crystals, all of which require time. Thus, maintaining carbonation conditions beyond the point where carbonation reaches the interior is necessary. In the later stages of carbonation, calcium carbonate crystal growth still requires supplemental water and CO 2 to ensure complete crystal growth and strength enhancement. Therefore, a 24-hour carbonation time at room temperature is deemed appropriate to ensure specimen performance and the integrity of carbonation. As shown in Fig. 9 (b), it is evident that the specimen exhibited a rapid temperature rise followed by a sharp drop within the first 15 minutes of carbonation, indicating that the LFS carbonation reaction is exothermic. A vigorous exothermic reaction occurred in the initial minutes of carbonation, resulting in a significant temperature increase. This reaction also led to the loss of bridging water (Wang et al. 2022 ), particularly between the 6th and 7th minute when the temperature rose from 36.1°C to 81.5°C. However, the carbonation process of the specimens did not closely mirror this temperature change curve. The rapid exothermic reaction in the first few minutes may be attributed to a swift gas-solid carbonation reaction in the outer layer of the specimen particles due to the rapid diffusion of CO 2 gas at the beginning of carbonation, followed by a slower liquid-solid or gas-liquid-solid carbonation reaction. CO 2 pressure In this study, we examined the characteristics of LFS specimens that were carbonated at room temperature (25°C) for 24 hours under varying CO 2 pressures. Figure 10 shows that the CO 2 pressure has a small effect on the properties of the specimens, and increasing the CO 2 pressure can increase the compressive strength of the specimens by a small amount, but there is not much change in the carbon sequestration rate. Therefore, CO 2 pressure is not the main factor affecting the carbonation effect under the carbonation system in this study. Discussion Following an exploration of the four influencing factors: water-solid ratio, water content, carbonation temperature, and carbonation time, and considering the research contributions of scholars (Gao et al. 2023 ; Kim et al 2021; Luo et al. 2021 ; Pan et al. 2012 ; Song et al 2021 ) it can be inferred that the carbonation behavior of LFS can be divided into five distinct processes: Diffusion of CO 2 Initially, the LFS specimen has lost some water after natural curing, leaving behind small pores. The infiltration of CO 2 into the specimen through the connecting holes is attributed to the concentration gradient-induced diffusion (Srivastava et al. 2021 ). Placing the specimen in a high-humidity reactor helps restore moisture to the surface and inside the pores through gas diffusion, creating a favorable condition for surface carbonation. Solubilization of CO 2 and γ-C 2 S The dissolution of CO 2 in the alkaline environment of the steel slag sample results in the formation of CO 3 2− ions, which contribute to accelerated carbonation (Pan et al. 2012 ). The reaction equation is expressed by Eq. (4). The migration of Ca 2+ ions will progressively occur from the interior to the surface of the particles, potentially dissolving in the interfacial water or adsorbing onto the particle's surface. The dissolved Ca 2+ from γ-C 2 S can persist with the matrix for a long time because γ-C 2 S hydration activity is extremely low and essentially unreactive with H 2 O. The reaction equation is expressed by Eq. (5) (Tan et al. 2022 ). CO 2 + H 2 O → CO 3 2− + 2H + (4) Ca 2 SiO 4 + H 2 O → 2Ca 2+ + H 4 SiO 4 + OH − (5) Diffusion of CO 3 2− and Ca 2+ The CO 3 2− ion will propagate through the interstitial bridging water between particles due to concentration gradients. Bridging water between the particles significantly accelerates the diffusion of CO 2 and Ca 2+ . Carbonated water gradually permeates the specimen and the interiors of the particles, reacting with the dissolved Ca 2+ in the water. Carbonation Reaction Ca 2+ and CO 3 2− interact within bridging water or at the particle surface, resulting in the formation of calcium carbonate precipitates, as expressed by Eq. (6). Carbonates primarily form at particle contact points and within capillaries. This early carbonate deposition has minimal impact on the overall pore space connectivity (Boone et al. 2014 ), which does not impact the subsequent diffusion of CO 2 . Ca 2+ + CO 3 2− → CaCO 3 (6) Nucleation and Growth of Calcium Carbonate Crystals The precipitation of calcium carbonate crystals is a gradual process encompassing the formation of nucleation sites, the persistent enrichment of Ca 2+ and CO 3 2− , and the gradual growth of crystals. Concurrently with the carbonation reaction and CO 2 diffusion, the high-strength calcium carbonate forms both internally and externally, ultimately leading to the hardening of the specimen. Notably, the most critical factor influencing carbonation efficiency is the rate of CO 2 diffusion (Zhong et al. 2021 ). To provide a comprehensive understanding of the carbonation process, this paper proposes a diffusion and reaction model, illustrated in Fig. 11 . Initially, after natural curing, the specimen experiences moisture loss on the surface, resulting in the formation of some surface holes. Simultaneously, the interior retains moisture. When placed in a high-humidity reactor, gas diffusion rapidly replenishes moisture on the surface and within the pores. The elevated humidity conditions promote favorable surface carbonation reactions, which is the initial phase of the carbonation process. Subsequently, moisture and CO 2 efficiently traverse the surface and enter the interior through gaseous diffusion. This swift ingress causes the surface's calcium carbonate products to diffuse into the interior before CO 2 achieves full formation and dissolution in the interior's moisture. The subsequent stages of carbonation rely on ionic diffusion of the solution for mass transfer. The presence of bridging water between particles greatly enhances the diffusion rates of CO 2 and Ca 2+ . This results in the efficient formation of high-strength calcium carbonate, both internally and externally, eventually leading to the hardening of the specimen. Conclusions In conclusion, this study has provided valuable insights into the production of a high-strength carbonated steel slag binder through pouring and molding. Several key findings have been established: (1) The water-solid ratio significantly impacts specimen density and strength, with lower ratios leading to greater denseness and increased strength. However, considering the challenges in the molding process, a water-solid ratio of 0.3 was deemed most practical. The water content of the specimen before carbonation emerged as a pivotal factor influencing carbonation mass transfer. Compressive strength and carbon sequestration rate exhibited an initial increase followed by a decrease with rising water content. Elevated water content supplied more medium for the carbonation reaction, promoting the process. Nevertheless, excessive water resulted in the formation of a water film on particle surfaces and pore blockage, inhibiting CO 2 diffusion. The optimal water content was determined to be 7%. (2) The compressive strength of LFS exhibited a declining trend with increasing temperature, while the carbon sequestration rate displayed an initial rise followed by a decrease. This behavior was attributed to temperature-induced reductions in CO 2 solubility, loss of free water, and accelerated substance dissolution and mass transfer. Notably, specimens carbonated at 20°C developed dense layered calcite, achieving a remarkable compressive strength of 120.5MPa. Higher temperatures fostered the proliferation of fine calcite crystals, with the highest carbon sequestration rate of 19.72% achieved at 60°C. Prolonging carbonation time improved the conversion rate of γ-C 2 S to calcite crystals. The initial 15 minutes represented a rapid CO 2 diffusion and reaction phase, yielding a compressive strength of 70.59MPa at 2 h of carbonation. Nearly complete carbonation was achieved after 18 h of carbonation. Increasing CO 2 pressure marginally enhanced specimen compressive strength, with minimal changes in the carbon sequestration rate. (3) During the carbonation process, the relatively dry surface portion initiated the carbonation reaction upon contact with CO 2 , which quickly permeated the surface and penetrated the interior through gas diffusion. Mass transfer in the moist interior primarily relied on ionic diffusion facilitated by bridging water, promoting CO 2 and Ca 2+ diffusion within the interior. Carbonated water reacted with dissolved Ca 2+ in the water, efficiently forming high-strength calcium carbonate both internally and externally. This process culminated in the creation of a high-strength carbonated binder. These findings contribute to the understanding of the intricate carbonation process and offer practical insights for the development of high-strength carbonated steel slag binders. Declarations Authorship contribution statement Ping Chen : Conceptualization, Methodology. ShenQiu Lin : Data Curation, Writing-Original Draft. WeiHeng Xiang : Formal analysis, Resources. Cheng Hu : Investigation, Writing-Review & Editing. FangBin Li : Supervision. Yu Ding : Validation. Competing Interests The authors have no relevant financial or non-financial interests to disclose. Ethical approval and Consent to Participate Written informed consent for publication of this paper was obtained from all authors. Consent to Publish The work described has not been published before; that it is not under consideration for publication anywhere else; that its publication has been approved by all co-authors. Funding The authors appreciate the financial support from the Guangxi Science Base and Talents Special Program (GuikeAD22035126), the Guangxi Natural Science Foundation project (2023GXNSFBA026130), and the Natural Science Foundation of China (No. 52368029 and No.52062009). 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J Environ Manage 167: 185-195. http://dx.doi.org/10.1016/j.jenvman.2015.11.042 Rui Y, Qian C (2022) CO 2 -fixing steel slag on hydration characteristics of cement-based materials. Constr Build Mater 354: 129193. https://doi.org/10.1016/j.conbuildmat.2022.129193 Song Q, Guo MZ, Wang L, Ling TC (2021) Use of steel slag as sustainable construction materials: A review of accelerated carbonation treatment. Resour Conserv Recy 173(1): 105740. https://doi.org/10.1016/j.resconrec.2021.105740 Srivastava S, Snellings R, Cool P (2021) Clinker-free carbonate-bonded (CFCB) products prepared by accelerated carbonation of steel furnace slags: A parametric overview of the process development. Constr Build Mater 303(5): 124556. https://doi.org/10.1016/j.conbuildmat.2021.124556 Tan Y, Liu Z, Wang F (2022) Effect of temperature on the carbonation behavior of γ-C 2 S compacts. Cement Concrete Comp 133: 104652. https://doi.org/10.1016/j.cemconcomp.2022.104652 Wang A, Ren P, Zeng Q, Ling TC (2022) Performance investigation and optimization of the granulation-CO 2 concentration for the production of high-strength BOFS aggregates. J CO 2 Util 64: 102160. https://doi.org/10.1016/j.jcou.2022.102160 Wray JL, Daniels F (1957) Precipitation of calcite and aragonite. J Am Chem Soc 79(9): 2031-2034. https://doi.org/10.1021/ja01566a001 Xu B, Yi Y (2022) Immobilization of lead (Pb) using ladle furnace slag and carbon dioxide. Chemosphere 308: 136387. https://doi.org/10.1016/j.chemosphere.2022.136387 Yi YR, Lin Y, Du YC, Bai SQ, Chen YG (2021) Accelerated carbonation of ladle furnace slag and characterization of its mineral phase. Constr Build Mater 276: 122235. https://doi.org/10.1016/j.conbuildmat.2020.122235 Zhang S, Ghouleh Z, Mucci A, Bahn O, Provençal R, Shao Y (2022) Production of cleaner high-strength cementing material using steel slag under elevated-temperature carbonation. J Clean Prod 342: 130948. https://doi.org/10.1016/j.jclepro.2022.130948 Zhang Y, Yu L, Cui K, Wang H, Fu T (2023) Carbon capture and storage technology by steel-making slags: Recent progress and future challenges. Chem Eng J 455: 140552. https://doi.org/10.1016/j.cej.2022.140552 Zhong X, Li L, Jiang Y, Ling TC (2021) Elucidating the dominant and interaction effects of temperature, CO 2 pressure and carbonation time in carbonating steel slag blocks. Constr Build Mater 302: 124158. https://doi.org/10.1016/j.conbuildmat.2021.124158 Cite Share Download PDF Status: Under Revision Version 1 posted Editorial decision: Major Revision 15 Apr, 2024 Reviewers agreed at journal 27 Dec, 2023 Reviewers invited by journal 27 Dec, 2023 Editor invited by journal 22 Dec, 2023 Editor assigned by journal 27 Nov, 2023 First submitted to journal 21 Nov, 2023 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-3621729","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":263819371,"identity":"0e384035-ee00-4b2f-8ae0-0aeb14ac0c56","order_by":0,"name":"Ping Chen","email":"","orcid":"","institution":"Guilin University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Ping","middleName":"","lastName":"Chen","suffix":""},{"id":263819372,"identity":"d3b06e92-c089-415c-a0d8-dc02356b1206","order_by":1,"name":"ShenQiu Lin","email":"","orcid":"","institution":"Guilin University of Technology","correspondingAuthor":false,"prefix":"","firstName":"ShenQiu","middleName":"","lastName":"Lin","suffix":""},{"id":263819373,"identity":"a7fe34bb-bd2f-4370-bfcc-4871443d80a1","order_by":2,"name":"WeiHeng Xiang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA6ElEQVRIie3PMWrDMBTGcRmBvDzIqg6NryDjIUMCGXqRpyVemkC3DhkeGOwxq7dcIbmBgqCTs2fMERy6p5U9ZFQ1FqL/IBB8P5AYi8X+YRPOjdH3xZSl453/TV6aWpterAo3TiiIqK4rTq2wmoIJu6CyALzcv8Hsyj7nmtKz8YqkRbQgxfpoISfWlZpgg17CJRoLCtbHypGkdi+UoLxESE0WUJb5SO4BBMCyU2sUZnwgFEBkWjNzI8wPXHy0+FUWNbz7ydJOvntNP1nWVIe+385fd2nnJ4+UcQcOvwvbuzIKnsZisdiz9QsWDEcZ/wnhSQAAAABJRU5ErkJggg==","orcid":"","institution":"Guilin University of Technology","correspondingAuthor":true,"prefix":"","firstName":"WeiHeng","middleName":"","lastName":"Xiang","suffix":""},{"id":263819374,"identity":"e8e90af2-0f59-437d-97bf-3a2fee46f415","order_by":3,"name":"Cheng Hu","email":"","orcid":"","institution":"Guilin University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Cheng","middleName":"","lastName":"Hu","suffix":""},{"id":263819375,"identity":"d14b1eb5-632a-4c04-b38e-6f2adcb7e68b","order_by":4,"name":"FangBin Li","email":"","orcid":"","institution":"Guilin University of Technology","correspondingAuthor":false,"prefix":"","firstName":"FangBin","middleName":"","lastName":"Li","suffix":""},{"id":263819376,"identity":"4024ff0f-42ae-468a-9eeb-45af51a2cfcd","order_by":5,"name":"Yu Ding","email":"","orcid":"","institution":"Guilin University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Yu","middleName":"","lastName":"Ding","suffix":""}],"badges":[],"createdAt":"2023-11-16 17:33:31","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3621729/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3621729/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":49021083,"identity":"e6c12868-fe3a-4d6a-93bb-11ccb26f8a4d","added_by":"auto","created_at":"2024-01-01 09:12:26","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":224705,"visible":true,"origin":"","legend":"\u003cp\u003eParticle size distribution (a) and X-ray diffraction pattern (b) of as-received LFS powder.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-3621729/v1/062bf2ea0e44cdc17c0b35e2.png"},{"id":49021395,"identity":"6e26af46-13aa-4ac0-aa74-612ce8475a61","added_by":"auto","created_at":"2024-01-01 09:20:26","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":56130,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic diagram of carbonation device.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-3621729/v1/a16c4e763a55b0e1cf6a61ed.png"},{"id":49021079,"identity":"78fcf001-8f3d-426f-b0d9-4f73a154af4c","added_by":"auto","created_at":"2024-01-01 09:12:26","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":35347,"visible":true,"origin":"","legend":"\u003cp\u003eThe effects of different water-solid ratios and water content on the compressive strength of the samples.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-3621729/v1/c33c7f17b7a703ebf722174d.png"},{"id":49021077,"identity":"8dee983e-3486-4072-9794-57aa4567186f","added_by":"auto","created_at":"2024-01-01 09:12:26","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":134770,"visible":true,"origin":"","legend":"\u003cp\u003e(a) The effect of water content on the properties of the sample; (b) Thermogravimetric curves of samples with different water contents.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-3621729/v1/a5b7b91550a450429855ae09.png"},{"id":49021396,"identity":"996c94c4-9730-473e-aea7-bd1ee6e519ce","added_by":"auto","created_at":"2024-01-01 09:20:26","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":52691,"visible":true,"origin":"","legend":"\u003cp\u003eX-ray spectra of samples with different water contents.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-3621729/v1/932e0e3e2e3863e1f133bbef.png"},{"id":49021085,"identity":"283200c3-7b1b-4ab7-aded-dce68e592c6a","added_by":"auto","created_at":"2024-01-01 09:12:26","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":177596,"visible":true,"origin":"","legend":"\u003cp\u003e(a) The effect of carbonation temperature on the properties of the sample; (b) X-ray spectra of samples under different carbonation temperatures.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-3621729/v1/aab4ba8a15fd1b9ec10a9bed.png"},{"id":49021398,"identity":"5b3c1383-b425-4761-ba87-622b19a8fd78","added_by":"auto","created_at":"2024-01-01 09:20:26","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":968931,"visible":true,"origin":"","legend":"\u003cp\u003eScanning electron microscope images at different carbonation temperatures: (a) 20℃; (b) 40℃; (c) 60℃; (d) 80℃.\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-3621729/v1/f736927d5fef7235b395a4c7.png"},{"id":49021397,"identity":"eaa6b7ac-465a-4c56-85b3-23ceea250f58","added_by":"auto","created_at":"2024-01-01 09:20:26","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":203050,"visible":true,"origin":"","legend":"\u003cp\u003e(a) The effect of carbonation time on the properties of the sample; (b) X-ray spectra of samples under different carbonation times.\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-3621729/v1/6ff24e01497d43c6c79b4cd1.png"},{"id":49021086,"identity":"1bdef562-5a87-47c1-a059-6e14edeed54c","added_by":"auto","created_at":"2024-01-01 09:12:26","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":640141,"visible":true,"origin":"","legend":"\u003cp\u003e(a) The section phenolphthalein color diagram of samples with different carbonation times; (b) Graph of the temperature at the center of the specimen with the carbonation time.\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-3621729/v1/f8fc520086f80edaaef4e3e3.png"},{"id":49021081,"identity":"e413e0df-2bb4-466c-86db-ab8a12ba5692","added_by":"auto","created_at":"2024-01-01 09:12:26","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":164381,"visible":true,"origin":"","legend":"\u003cp\u003e(a)The effect of CO\u003csub\u003e2\u003c/sub\u003e pressure on the properties of the sample; (b)X-ray spectra of samples under different CO\u003csub\u003e2\u003c/sub\u003e pressures.\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-3621729/v1/241d050bce43f86a3feb397d.png"},{"id":49021087,"identity":"5b85855e-d8b1-45b5-a169-a4cba405fbeb","added_by":"auto","created_at":"2024-01-01 09:12:26","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":361284,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic diagram of carbonation of steel slag\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-3621729/v1/07f523acceee8b73260531e9.png"},{"id":49021448,"identity":"acfd870b-8837-4d26-9f3e-4684839b5eac","added_by":"auto","created_at":"2024-01-01 09:28:32","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3246300,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3621729/v1/e477f022-0438-4685-a717-f4eedf6d0783.pdf"}],"financialInterests":"","formattedTitle":"\u003cp\u003eStudy on preparation and CO\u003csub\u003e2\u003c/sub\u003e sequestration mechanism of high-strength carbonated Ladle refining slag binder\u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003eIn recent years, global CO\u003csub\u003e2\u003c/sub\u003e emissions have surged due to rapid industrialization, surpassing 3\u0026nbsp;billion tons annually (Li et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), resulting in climate warming and rising sea levels (Fu et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Among the major contributors to carbon emissions, the construction industry stands out, with a staggering 9.95 Gt/y of CO\u003csub\u003e2\u003c/sub\u003e emissions (Hanifa et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). To promote sustainable and low-carbon practices in the building materials sector, researchers worldwide have developed various technologies to reduce carbon emissions associated with cement-based materials. Employing carbon capture and storage (CCS) technology stands as a promising method for mitigating the greenhouse effect (Fu et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Liu et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Pan et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). Meanwhile, steel slag, a predominant by-product of iron and steel production, continues to accumulate, exceeding 250\u0026nbsp;million tons annually on a global scale (Zhang et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). In China alone, steel slag production exceeds 120\u0026nbsp;million tons (Gao et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Unfortunately, steel slag faces significant challenges due to its high free CaO content, poor abrasiveness, and low hydration activity (Song et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). As a result, its utilization rate remains below 30% (Rui et al. 2022), with most of it ending up in landfills (Najm et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), posing environmental risks due to leaching alkaline ions and heavy metal ions.\u003c/p\u003e \u003cp\u003eNotably, steel slag can be categorized into different types based on production processes, with the Ladle Refining Slag (LFS) being a by-product of secondary or alkaline steelmaking (Espinosa et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). LFS primarily comprises γ-Ca\u003csub\u003e2\u003c/sub\u003eSiO\u003csub\u003e4\u003c/sub\u003e (γ-C\u003csub\u003e2\u003c/sub\u003eS), CaO, MgO, and other minerals (Xu et al. 2022; Zhang et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). The extremely low hydration activity of γ-C\u003csub\u003e2\u003c/sub\u003eS significantly limits LFS utilization. Recent findings, however, have uncovered the carbonation potential of silicate minerals, particularly γ-C\u003csub\u003e2\u003c/sub\u003eS (Mu et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2019\u003c/span\u003e), suggesting the possibility of efficiently converting LFS using CCS technology to create carbonated steel slag-based binders with exceptional performance.\u003c/p\u003e \u003cp\u003eWhile numerous studies have explored the carbonation behavior of steel slag, most have focused on Basic Oxygen Furnace Slag (BOFS). For instance, BOFS specimens have demonstrated strengths of up to 80 MPa in just 2 h (Ghouleh et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Current LFS studies are very limited and mostly focused on CO\u003csub\u003e2\u003c/sub\u003e curing of heavy metals (Xu et al. 2022). However, there is untapped potential in LFS carbonation, and understanding the influencing factors of the preparation process is crucial. Researchers have predominantly focused on variables like temperature, carbonation time, and CO\u003csub\u003e2\u003c/sub\u003e pressure (Luo et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Zhong et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), overlooking the impact of specimen water content, which can significantly influence carbonation product formation. Additionally, most studies have employed pressed shaping methods (Chang et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Ghouleh et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Mahoutian et al. \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Zhang et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Zhong et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), which have been successful in achieving impressive strengths. Leaving gaps in our understanding of pouring and molding, a common engineering practice.\u003c/p\u003e \u003cp\u003eThis study aims to develop an energy-efficient, low-carbon, high-strength carbonated LFS binder using pouring and molding techniques. It systematically investigates water-solid ratio and water content, carbonation temperature, carbonation time, and CO\u003csub\u003e2\u003c/sub\u003e pressure's effects on carbonated LFS performance to derive an optimal preparation process. The study delves into the influence of water on CO\u003csub\u003e2\u003c/sub\u003e diffusion, observes the morphology of carbonation products at various temperatures, and derives a theoretical diffusion model for the carbonation process of steel slag. These findings pave the way for the utilization of carbonated steel slag in bricks, prefabricated components, cementitious materials, and more, addressing steel slag stockpiling issues and enabling low-carbon or even carbon-negative production in the building materials industry through CCS technology.\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n \u003ch2\u003eRaw material\u003c/h2\u003e\n \u003cp\u003eIn this paper, Ladle Refining Slag (LFS) utilized originated from Guangxi Beibu Gulf New Material Co., Ltd. The chemical composition of LFS is detailed in Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e. The K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e employed is a chemically pure reagent with a purity of 99.95% (AR), while the CO\u003csub\u003e2\u003c/sub\u003e utilized is of industrial grade, boasting a purity level of 99%. The LFS was initially subjected to ball milling for 1 hour, followed by screening through a 100-mesh sieve.\u003c/p\u003e\n \u003cp\u003eIn Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e(a), the primary particle size distribution of LFS micro powders, following milling and sieving, ranged from 0.2 to 20 \u0026micro;m, with an average particle size distribution D50 of 2.77 \u0026micro;m. As shown in Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e(b), the primary physical phase compositions of LFS included \u0026gamma;-Ca\u003csub\u003e2\u003c/sub\u003eSiO\u003csub\u003e4\u003c/sub\u003e (\u0026gamma;-C\u003csub\u003e2\u003c/sub\u003eS), Ca\u003csub\u003e2\u003c/sub\u003eMg(Si\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e7\u003c/sub\u003e), and Mg\u003csub\u003e2\u003c/sub\u003eSiO\u003csub\u003e6\u003c/sub\u003e. It was shown that Mg\u003csup\u003e+\u003c/sup\u003e can also participate in the carbonation reaction (Baciocchi et al. \u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e; Polettini et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e; Yi et al. \u003cspan class=\"CitationRef\"\u003e2021\u003c/span\u003e). Considering the favorable carbonation activity of LFS, this suggests that LFS can be utilized to produce carbonated steel slag-based binders with outstanding mechanical properties through carbonation reactions.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eChemical compositions of LFS(wt%).\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eOxides\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCaO\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSiO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMgO\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eTiO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eFe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eothers\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLFS\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e69.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e22.56\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.81\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.49\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.35\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n \u003ch2\u003ePreparation process and reaction equipment\u003c/h2\u003e\n \u003cp\u003eLFS micro powder and water were combined in a net slurry mixer in accordance with water-solid ratios of 0.25, 0.3, and 0.35. The mixture was blended for 4 minutes, after which it was cast into 20\u0026times;20\u0026times;20mm cube molds for shaping. After undergoing 24 hours of natural curing at ambient temperature, the molds were removed and the specimens were subsequently dried in the air at room temperature (25\u0026deg;C) for varying durations. This step was performed to attain a final water content ranging from 0\u0026ndash;10% prior to carbonation, which was determined using Eq.\u0026nbsp;(1). Subsequently, the specimens were placed in a carbonation kettle under a vacuum pressure of -0.8MPa, at temperatures ranging from 20\u0026ndash;80\u0026deg;C, and a CO\u003csub\u003e2\u003c/sub\u003e pressure of 0.1-0.4MPa for a 24h carbonation reaction. Following the completion of the reaction, microstructural and property tests were conducted.\u003c/p\u003e\n \u003cp\u003e\u003cem\u003ew\u003c/em\u003e%=(\u003cem\u003eM\u003c/em\u003e\u003csub\u003e1\u003c/sub\u003e-\u003cem\u003eM\u003c/em\u003e\u003csub\u003e2\u003c/sub\u003e)/\u003cem\u003eM\u003c/em\u003e\u003csub\u003e2\u003c/sub\u003e\u0026times;100% (1)\u003c/p\u003e\n \u003cp\u003eThe water content of the specimen, denoted as \u003cem\u003ew\u003c/em\u003e%, is controlled within an error range of \u0026plusmn;\u0026thinsp;0.1%. \u003cem\u003eM\u003c/em\u003e\u003csub\u003e1\u003c/sub\u003e represents the weight of the wet base specimen, which can be determined by weighing the carbonated sample. \u003cem\u003eM\u003c/em\u003e\u003csub\u003e2\u003c/sub\u003e corresponds to the weight of the dry base specimen, obtained by completely drying a parallel set of specimens from the same group. The weighing process ensures that errors are limited to 0.1%; otherwise, retesting is required.\u003c/p\u003e\n \u003cp\u003eThe carbonation equipment used in the test mainly consists of a carbonation reactor, water bath, vacuum pump, and industrial pure CO\u003csub\u003e2\u003c/sub\u003e cylinder, see Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e. Saturated K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e solution was placed at the bottom of the reactor to maintain high humidity inside the kettle, and the humidity could be maintained above 90% at 20\u0026ndash;80℃. With the bracket and the metal, the mesh would be carbonated samples above the saturated solution surface to ensure that the CO\u003csub\u003e2\u003c/sub\u003e and water are fully in contact with the surface of the specimen.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n \u003ch2\u003eTest methods\u003c/h2\u003e\n \u003cp\u003eThe compressive strength of the specimens was tested in accordance with the standard GB/T 17671\u0026thinsp;\u0026minus;\u0026thinsp;2021. The X-ray diffraction pattern test was conducted using an X`Pert PRO X-ray diffractometer from PANalytical, the Netherlands, equipped with a Cu K\u0026alpha; (\u0026lambda;\u0026thinsp;=\u0026thinsp;1.5406\u0026Aring;) X-ray source and a scanning range of 2\u0026theta; from 5 to 80\u0026deg;. Microscopic morphology analysis was performed using a Zeiss model S-4800 scanning electron microscope with an accelerating voltage of 5 kV. Temperature changes during carbonation were recorded by inserting a temperature probe from a continuous pyrometer (T20BL-EX) into the center of the specimen after formation. The specimen was then placed in the carbonation kettle at room temperature, and the temperature change curve over time was measured. The carbon sequestration rate of the specimen was analyzed using thermogravimetry (TGA) according to the calculations shown in Eq.\u0026nbsp;(\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e) and Eq.\u0026nbsp;(\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e) (Li et al. \u003cspan class=\"CitationRef\"\u003e2021\u003c/span\u003e). The testing temperature ranged from 25\u0026deg;C to 1000\u0026deg;C, with a heating rate of 5\u0026deg;C/min, in a nitrogen atmosphere.\u003c/p\u003e\n \u003cp\u003e\u003cimg 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\" width=\"798\" height=\"138\"\u003e\u003c/p\u003e\n \u003cp\u003eWhere CO\u003csub\u003e2\u003c/sub\u003e(\u003cem\u003ewt\u003c/em\u003e.%) denotes the rate of CO\u003csub\u003e2\u003c/sub\u003e loss, ∆m\u003csub\u003eCO2\u003c/sub\u003e denotes the rate of mass loss during the decomposition of calcium carbonate to produce CO\u003csub\u003e2\u003c/sub\u003e at elevated temperatures of the specimen, m\u003csub\u003e105\u0026deg;C\u003c/sub\u003e denotes the weight of the specimen after drying, CO\u003csub\u003e2\u003cem\u003euptake\u003c/em\u003e\u003c/sub\u003e(wt.%) denotes the rate of carbon sequestration, and CO\u003csub\u003e2carbonated\u003c/sub\u003e(wt.%) denotes the rate of CO\u003csub\u003e2\u003c/sub\u003e loss after carbonation of the specimen. CO\u003csub\u003e2initial\u003c/sub\u003e(wt.%) indicates the CO\u003csub\u003e2\u003c/sub\u003e loss rate of the uncarbonated specimen.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Results and discussion","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\n \u003ch2\u003ewater-solid ratio and water content\u003c/h2\u003e\n \u003cp\u003eIn this study, we examined the characteristics of LFS specimens with varying water-solids ratios and water contents, which were carbonated for 24 hours at room temperature (25\u0026deg;C) and a CO\u003csub\u003e2\u003c/sub\u003e pressure of 0.4 MPa. The resulting compressive strengths for each specimen are depicted in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e. Notably, the compressive strength of the specimens exhibited a decreasing trend as the water-solid ratio increased. This was attributed to the fact that specimens with lower water-solid ratios tend to be denser and less porous, leading to an optimal compressive strength of 113.5MPa observed at a water-solid ratio of 0.25 and a water content of 7%. However, a higher water-solid ratio offers improved pourability and moldability, prompting the selection of a water-solid ratio of 0.3 for subsequent tests.\u003c/p\u003e\n \u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e, the compressive strength and carbon sequestration rate of the specimens displayed an initial increase followed by a decline with increasing water content. This phenomenon is attributed to the higher water content providing an increased supply of water for the carbonation reaction, resulting in a greater degree of carbonation for \u0026gamma;-C\u003csub\u003e2\u003c/sub\u003eS and other active components. Consequently, more calcium carbonate is generated, contributing to enhanced compressive strength and carbon sequestration rates. This is supported by the intensification of calcium carbonate diffraction peaks and the weakening of \u0026gamma;-C\u003csub\u003e2\u003c/sub\u003eS diffraction peaks in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e. The peak performance was achieved when the water content reached 7%, as at this point, the appropriate water content facilitated bridging between particles, bonding them together without excessively affecting carbonation on the particle surfaces. This allowed for deep penetration of carbonation into the specimen\u0026apos;s interior, ensuring effective dissolution of Ca\u003csup\u003e2+\u003c/sup\u003e and CO\u003csub\u003e2\u003c/sub\u003e. Consequently, calcium carbonate crystals could grow successively, yielding specimens with a compressive strength of up to 90.08MPa and a carbon sequestration rate of 18.09%.\u003c/p\u003e\n \u003cp\u003eHowever, further increases in water content led to a sharp decline in performance. Specimens with water content of 8% and above exhibited compressive strengths of only about 5MPa, with XRD analysis revealing pronounced \u0026gamma;-C\u003csub\u003e2\u003c/sub\u003eS diffraction peaks. This decline is attributed to the formation of a \u0026quot;water film\u0026quot; on the specimen and particle surfaces due to high water content, hindering CO\u003csub\u003e2\u003c/sub\u003e diffusion into the interior. Excess water also clogged the steel slag mass\u0026apos;s pores, impeding CO\u003csub\u003e2\u003c/sub\u003e diffusion further.\u003c/p\u003e\n \u003cp\u003eIn conclusion, water content plays a critical role in the characteristics of carbonated specimens, primarily due to its role as a medium for Ca\u003csup\u003e2+\u003c/sup\u003e and CO\u003csub\u003e2\u003c/sub\u003e dissolution, which is crucial for CO\u003csub\u003e2\u003c/sub\u003e diffusion\u0026mdash;a key determinant of the early carbonation rate (Zhong et al. \u003cspan class=\"CitationRef\"\u003e2021\u003c/span\u003e). Thus, the forming optimal process parameters for LFS were determined to be a water-solid ratio of 0.3 and a water content of 7%.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n \u003ch2\u003eCarbonation temperature\u003c/h2\u003e\n \u003cp\u003eIn this study, we investigated the properties and microstructures of LFS specimens that were carbonated at varying temperatures for a duration of 24 hours, under a CO\u003csub\u003e2\u003c/sub\u003e pressure of 0.4 MPa. In Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e(a), it is evident that the compressive strength of carbonated LFS at 20\u0026deg;C reaches an impressive 120.5MPa. However, as the carbonation temperature increases, the compressive strength of the specimen gradually decreases. This phenomenon may be attributed to the elevated temperature affecting the stable growth of calcium carbonate crystals. Research has indicated that laboratory-synthesized calcium carbonate can undergo interconversion between calcite, aragonite, and spherulite at specific temperatures (Wray et al. 1957). Higher temperatures reduce the solubility of CO\u003csub\u003e2\u003c/sub\u003e, and the increased internal temperature leads to faster evaporation of free water, resulting in limited leaching of calcium ions and reduced CO\u003csub\u003e2\u003c/sub\u003e solubilization (Humbert et al. \u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e; Luo et al. \u003cspan class=\"CitationRef\"\u003e2021\u003c/span\u003e). These factors contribute to the decline in strength.\u003c/p\u003e\n \u003cp\u003eInterestingly, the carbon sequestration rate exhibited an initial increase followed by a decrease with increasing temperature, mirroring the pattern of calcium carbonate peaks observed in the XRD pattern in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e(b). The initial increase is likely due to the higher temperature leading to faster dissolution and mass transfer of substances, resulting in a deeper carbonation depth at the microscopic level and an increased carbon sequestration rate. For instance, the sample carbonated at 60\u0026deg;C exhibited the highest carbon sequestration rate of 19.72%, whereas at 80\u0026deg;C, this rate dropped to 15.02%.\u003c/p\u003e\n \u003cp\u003eThe decline in the carbon sequestration rate at higher temperatures can be attributed to several factors. Firstly, the elevated temperature causes excessive water loss within the specimen, disrupting the optimal water content required before carbonation. Secondly, the high temperature leads to an increased generation of water vapor at the bottom of the equipment, causing water to adhere to the specimen\u0026apos;s surface. This, in turn, hinders mass transfer and the carbonation reaction.\u003c/p\u003e\n \u003cp\u003eFigure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e illustrates how the morphology of carbonated LFS becomes increasingly irregular with rising temperature. Smaller calcium carbonate crystals are observed, and the pores become more porous as the temperature increases. This irregular morphology may explain the decrease in compressive strength observed at higher temperatures.\u003c/p\u003e\n \u003cp\u003eSpecimens carbonated at 20\u0026deg;C exhibit slower growth of calcium carbonate crystals due to the lower temperature environment. This results in better densification of the matrix between the powder particles, yielding dense, massive, layered calcite (Fig. \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e(a)), which explains the high compressive strength. In contrast, specimens carbonated at 40\u0026deg;C exhibit various morphologies of calcite and aragonite crystals, such as shells, rods, flakes, blocks, and petals (Fig. \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e(b)). Those carbonated at 60\u0026deg;C still display blocky calcite and petaloid aragonite/vaterite (Fig. \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e(c)), while at 80\u0026deg;C, an irregular morphology is observed, with a profusion of fine crystals and gels encapsulating the particles (Fig. \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e(d)). This phenomenon can prevent effective carbonation within the particles, contributing to the reduced carbon sequestration rate at higher temperatures.\u003c/p\u003e\n \u003cp\u003eIn summary, the increase in temperature does not necessarily enhance the efficiency of the LFS carbonation reaction. While higher temperatures initially improve the reaction rate and generate many small carbonation product particles with a high carbon sequestration rate, they subsequently lead to the rapid encapsulation of particles by the carbonation product layer. Moreover, higher temperatures decrease the solubility of CO\u003csub\u003e2\u003c/sub\u003e, resulting in reduced carbonation efficiency.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\n \u003ch2\u003eCarbonation time\u003c/h2\u003e\n \u003cp\u003eIn this study, we examined the characteristics and degree of carbonation of LFS specimens that were carbonated for varying periods at room temperature (25\u0026deg;C) and CO\u003csub\u003e2\u003c/sub\u003e pressure of 0.4 MPa. As depicted in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e(a), both the compressive strength and carbon sequestration rate of the specimens increased over time. This increase was particularly rapid in the initial 2 hours, reaching a compressive strength of 70.59MPa and a carbon sequestration rate of 16.27% after 2 hours of carbonation. Subsequently, at the 18-hour mark, the strength and carbon sequestration rate essentially reached saturation, with minimal further increases with extended carbonation time.\u003c/p\u003e\n \u003cp\u003eFigure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e(b) also reveals that the diffraction peaks of \u0026gamma;-C\u003csub\u003e2\u003c/sub\u003eS weakened as carbonation time increased, while the diffraction peaks of calcite became stronger. This observation suggests that \u0026gamma;-C\u003csub\u003e2\u003c/sub\u003eS gradually transformed into calcite crystals during the carbonation process, contributing to the rise in compressive strength and carbon sequestration rate.\u003c/p\u003e\n \u003cp\u003eTo visualize the depth of carbonation, a phenolphthalein indicator was applied to the middle section of the carbonated specimen. Uncarbonated alkaline steel slag remained red, while the carbonated area showed no color, as depicted in Fig. \u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e(a). Carbonation progressed rapidly within the first hour, with CO\u003csub\u003e2\u003c/sub\u003e diffusion and dissolution reaching the interior within this timeframe or even earlier. By the 2-h mark, carbonation had penetrated deep into the interior, and specimens carbonated for 4 h or longer displayed no color change after phenolphthalein application. However, it\u0026apos;s important to note that carbonation is a gradual process, involving the diffusion and dissolution of reactive substances and the nucleation and growth of crystals, all of which require time. Thus, maintaining carbonation conditions beyond the point where carbonation reaches the interior is necessary. In the later stages of carbonation, calcium carbonate crystal growth still requires supplemental water and CO\u003csub\u003e2\u003c/sub\u003e to ensure complete crystal growth and strength enhancement. Therefore, a 24-hour carbonation time at room temperature is deemed appropriate to ensure specimen performance and the integrity of carbonation.\u003c/p\u003e\n \u003cp\u003eAs shown in Fig. \u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e(b), it is evident that the specimen exhibited a rapid temperature rise followed by a sharp drop within the first 15 minutes of carbonation, indicating that the LFS carbonation reaction is exothermic. A vigorous exothermic reaction occurred in the initial minutes of carbonation, resulting in a significant temperature increase. This reaction also led to the loss of bridging water (Wang et al. \u003cspan class=\"CitationRef\"\u003e2022\u003c/span\u003e), particularly between the 6th and 7th minute when the temperature rose from 36.1\u0026deg;C to 81.5\u0026deg;C. However, the carbonation process of the specimens did not closely mirror this temperature change curve. The rapid exothermic reaction in the first few minutes may be attributed to a swift gas-solid carbonation reaction in the outer layer of the specimen particles due to the rapid diffusion of CO\u003csub\u003e2\u003c/sub\u003e gas at the beginning of carbonation, followed by a slower liquid-solid or gas-liquid-solid carbonation reaction.\u003c/p\u003e\n \u003cdiv id=\"Sec10\" class=\"Section3\"\u003e\n \u003ch2\u003eCO\u003csub\u003e2\u003c/sub\u003e pressure\u003c/h2\u003e\n \u003cp\u003eIn this study, we examined the characteristics of LFS specimens that were carbonated at room temperature (25\u0026deg;C) for 24 hours under varying CO\u003csub\u003e2\u003c/sub\u003e pressures. Figure \u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e shows that the CO\u003csub\u003e2\u003c/sub\u003e pressure has a small effect on the properties of the specimens, and increasing the CO\u003csub\u003e2\u003c/sub\u003e pressure can increase the compressive strength of the specimens by a small amount, but there is not much change in the carbon sequestration rate. Therefore, CO\u003csub\u003e2\u003c/sub\u003e pressure is not the main factor affecting the carbonation effect under the carbonation system in this study.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eFollowing an exploration of the four influencing factors: water-solid ratio, water content, carbonation temperature, and carbonation time, and considering the research contributions of scholars (Gao et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Kim et al 2021; Luo et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Pan et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Song et al \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) it can be inferred that the carbonation behavior of LFS can be divided into five distinct processes:\u003c/p\u003e \u003cp\u003e \u003cstrong\u003eDiffusion of CO\u003csub\u003e2\u003c/sub\u003e\u003c/strong\u003e \u003cp\u003eInitially, the LFS specimen has lost some water after natural curing, leaving behind small pores. The infiltration of CO\u003csub\u003e2\u003c/sub\u003e into the specimen through the connecting holes is attributed to the concentration gradient-induced diffusion (Srivastava et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Placing the specimen in a high-humidity reactor helps restore moisture to the surface and inside the pores through gas diffusion, creating a favorable condition for surface carbonation.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eSolubilization of CO\u003csub\u003e2\u003c/sub\u003e and γ-C\u003csub\u003e2\u003c/sub\u003eS\u003c/strong\u003e \u003cp\u003eThe dissolution of CO\u003csub\u003e2\u003c/sub\u003e in the alkaline environment of the steel slag sample results in the formation of CO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e ions, which contribute to accelerated carbonation (Pan et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). The reaction equation is expressed by Eq.\u0026nbsp;(4). The migration of Ca\u003csup\u003e2+\u003c/sup\u003e ions will progressively occur from the interior to the surface of the particles, potentially dissolving in the interfacial water or adsorbing onto the particle's surface. The dissolved Ca\u003csup\u003e2+\u003c/sup\u003e from γ-C\u003csub\u003e2\u003c/sub\u003eS can persist with the matrix for a long time because γ-C\u003csub\u003e2\u003c/sub\u003eS hydration activity is extremely low and essentially unreactive with H\u003csub\u003e2\u003c/sub\u003eO. The reaction equation is expressed by Eq.\u0026nbsp;(5) (Tan et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cem\u003eCO\u003c/em\u003e \u003csub\u003e \u003cem\u003e2\u003c/em\u003e \u003c/sub\u003e\u0026thinsp;\u003cem\u003e+\u0026thinsp;H\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003cem\u003eO\u003c/em\u003e \u0026rarr; \u003cem\u003eCO\u003c/em\u003e\u003csub\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sub\u003e\u003csup\u003e\u003cem\u003e2\u0026minus;\u003c/em\u003e\u003c/sup\u003e \u003cem\u003e+ 2H\u003c/em\u003e\u003csup\u003e\u003cem\u003e+\u003c/em\u003e\u003c/sup\u003e (4)\u003c/p\u003e \u003cp\u003e \u003cem\u003eCa\u003c/em\u003e \u003csub\u003e \u003cem\u003e2\u003c/em\u003e \u003c/sub\u003e \u003cem\u003eSiO\u003c/em\u003e \u003csub\u003e \u003cem\u003e4\u003c/em\u003e \u003c/sub\u003e\u0026thinsp;\u003cem\u003e+\u0026thinsp;H\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003cem\u003eO\u003c/em\u003e \u0026rarr; \u003cem\u003e2Ca\u003c/em\u003e\u003csup\u003e\u003cem\u003e2+\u003c/em\u003e\u003c/sup\u003e \u003cem\u003e+ H\u003c/em\u003e\u003csub\u003e\u003cem\u003e4\u003c/em\u003e\u003c/sub\u003e\u003cem\u003eSiO\u003c/em\u003e\u003csub\u003e\u003cem\u003e4\u003c/em\u003e\u003c/sub\u003e\u0026thinsp;\u003cem\u003e+\u0026thinsp;OH\u003c/em\u003e\u003csup\u003e\u003cem\u003e\u0026minus;\u003c/em\u003e\u003c/sup\u003e (5)\u003c/p\u003e \u003cp\u003e \u003cstrong\u003eDiffusion of CO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e and Ca\u003csup\u003e2+\u003c/sup\u003e\u003c/strong\u003e \u003cp\u003eThe CO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e ion will propagate through the interstitial bridging water between particles due to concentration gradients. Bridging water between the particles significantly accelerates the diffusion of CO\u003csub\u003e2\u003c/sub\u003e and Ca\u003csup\u003e2+\u003c/sup\u003e. Carbonated water gradually permeates the specimen and the interiors of the particles, reacting with the dissolved Ca\u003csup\u003e2+\u003c/sup\u003e in the water.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eCarbonation Reaction\u003c/strong\u003e \u003cp\u003eCa\u003csup\u003e2+\u003c/sup\u003e and CO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e interact within bridging water or at the particle surface, resulting in the formation of calcium carbonate precipitates, as expressed by Eq.\u0026nbsp;(6). Carbonates primarily form at particle contact points and within capillaries. This early carbonate deposition has minimal impact on the overall pore space connectivity (Boone et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2014\u003c/span\u003e), which does not impact the subsequent diffusion of CO\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cem\u003eCa\u003c/em\u003e \u003csup\u003e \u003cem\u003e2+\u003c/em\u003e \u003c/sup\u003e \u003cem\u003e+ CO\u003c/em\u003e\u003csub\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sub\u003e\u003csup\u003e\u003cem\u003e2\u0026minus;\u003c/em\u003e\u003c/sup\u003e \u003cem\u003e\u0026rarr; CaCO\u003c/em\u003e\u003csub\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sub\u003e (6)\u003c/p\u003e \u003cp\u003e \u003cstrong\u003eNucleation and Growth of Calcium Carbonate Crystals\u003c/strong\u003e \u003cp\u003eThe precipitation of calcium carbonate crystals is a gradual process encompassing the formation of nucleation sites, the persistent enrichment of Ca\u003csup\u003e2+\u003c/sup\u003e and CO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e, and the gradual growth of crystals. Concurrently with the carbonation reaction and CO\u003csub\u003e2\u003c/sub\u003e diffusion, the high-strength calcium carbonate forms both internally and externally, ultimately leading to the hardening of the specimen.\u003c/p\u003e \u003c/p\u003e \u003cp\u003eNotably, the most critical factor influencing carbonation efficiency is the rate of CO\u003csub\u003e2\u003c/sub\u003e diffusion (Zhong et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). To provide a comprehensive understanding of the carbonation process, this paper proposes a diffusion and reaction model, illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e. Initially, after natural curing, the specimen experiences moisture loss on the surface, resulting in the formation of some surface holes. Simultaneously, the interior retains moisture. When placed in a high-humidity reactor, gas diffusion rapidly replenishes moisture on the surface and within the pores. The elevated humidity conditions promote favorable surface carbonation reactions, which is the initial phase of the carbonation process.\u003c/p\u003e \u003cp\u003eSubsequently, moisture and CO\u003csub\u003e2\u003c/sub\u003e efficiently traverse the surface and enter the interior through gaseous diffusion. This swift ingress causes the surface's calcium carbonate products to diffuse into the interior before CO\u003csub\u003e2\u003c/sub\u003e achieves full formation and dissolution in the interior's moisture. The subsequent stages of carbonation rely on ionic diffusion of the solution for mass transfer. The presence of bridging water between particles greatly enhances the diffusion rates of CO\u003csub\u003e2\u003c/sub\u003e and Ca\u003csup\u003e2+\u003c/sup\u003e. This results in the efficient formation of high-strength calcium carbonate, both internally and externally, eventually leading to the hardening of the specimen.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eIn conclusion, this study has provided valuable insights into the production of a high-strength carbonated steel slag binder through pouring and molding. Several key findings have been established:\u003c/p\u003e \u003cp\u003e(1) The water-solid ratio significantly impacts specimen density and strength, with lower ratios leading to greater denseness and increased strength. However, considering the challenges in the molding process, a water-solid ratio of 0.3 was deemed most practical. The water content of the specimen before carbonation emerged as a pivotal factor influencing carbonation mass transfer. Compressive strength and carbon sequestration rate exhibited an initial increase followed by a decrease with rising water content. Elevated water content supplied more medium for the carbonation reaction, promoting the process. Nevertheless, excessive water resulted in the formation of a water film on particle surfaces and pore blockage, inhibiting CO\u003csub\u003e2\u003c/sub\u003e diffusion. The optimal water content was determined to be 7%.\u003c/p\u003e \u003cp\u003e(2) The compressive strength of LFS exhibited a declining trend with increasing temperature, while the carbon sequestration rate displayed an initial rise followed by a decrease. This behavior was attributed to temperature-induced reductions in CO\u003csub\u003e2\u003c/sub\u003e solubility, loss of free water, and accelerated substance dissolution and mass transfer. Notably, specimens carbonated at 20\u0026deg;C developed dense layered calcite, achieving a remarkable compressive strength of 120.5MPa. Higher temperatures fostered the proliferation of fine calcite crystals, with the highest carbon sequestration rate of 19.72% achieved at 60\u0026deg;C. Prolonging carbonation time improved the conversion rate of γ-C\u003csub\u003e2\u003c/sub\u003eS to calcite crystals. The initial 15 minutes represented a rapid CO\u003csub\u003e2\u003c/sub\u003e diffusion and reaction phase, yielding a compressive strength of 70.59MPa at 2 h of carbonation. Nearly complete carbonation was achieved after 18 h of carbonation. Increasing CO\u003csub\u003e2\u003c/sub\u003e pressure marginally enhanced specimen compressive strength, with minimal changes in the carbon sequestration rate.\u003c/p\u003e \u003cp\u003e(3) During the carbonation process, the relatively dry surface portion initiated the carbonation reaction upon contact with CO\u003csub\u003e2\u003c/sub\u003e, which quickly permeated the surface and penetrated the interior through gas diffusion. Mass transfer in the moist interior primarily relied on ionic diffusion facilitated by bridging water, promoting CO\u003csub\u003e2\u003c/sub\u003e and Ca\u003csup\u003e2+\u003c/sup\u003e diffusion within the interior. Carbonated water reacted with dissolved Ca\u003csup\u003e2+\u003c/sup\u003e in the water, efficiently forming high-strength calcium carbonate both internally and externally. This process culminated in the creation of a high-strength carbonated binder.\u003c/p\u003e \u003cp\u003eThese findings contribute to the understanding of the intricate carbonation process and offer practical insights for the development of high-strength carbonated steel slag binders.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthorship contribution statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePing Chen\u003c/strong\u003e: Conceptualization, Methodology. \u003cstrong\u003eShenQiu Lin\u003c/strong\u003e: Data Curation, Writing-Original Draft. \u003cstrong\u003eWeiHeng Xiang\u003c/strong\u003e: Formal analysis, Resources. \u003cstrong\u003eCheng Hu\u003c/strong\u003e: Investigation, Writing-Review \u0026amp; Editing. \u003cstrong\u003eFangBin Li\u003c/strong\u003e: Supervision. \u003cstrong\u003eYu Ding\u003c/strong\u003e: Validation.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors have no relevant financial or non-financial interests to disclose.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical approval and Consent to Participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWritten informed consent for publication of this paper was obtained from all authors.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to Publish\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe work described has not been published before; that it is not under consideration for publication anywhere else; that its publication has been approved by all co-authors.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors appreciate the financial support from the Guangxi Science Base and Talents Special Program (GuikeAD22035126), the Guangxi Natural Science Foundation project (2023GXNSFBA026130), and the Natural Science Foundation of China (No. 52368029 and No.52062009).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe data are available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eBaciocchi R, Costa G, Di Gianfilippo M, Polettini A, Pomi R, Stramazzo A (2015) Thin-film versus slurry-phase carbonation of steel slag: CO\u003csub\u003e2\u003c/sub\u003e uptake and effects on mineralogy. 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Constr Build Mater 302: 124158. https://doi.org/10.1016/j.conbuildmat.2021.124158\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"environmental-science-and-pollution-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"espr","sideBox":"Learn more about [Environmental Science and Pollution Research](https://www.springer.com/journal/11356)","snPcode":"11356","submissionUrl":"https://submission.nature.com/new-submission/11356/3","title":"Environmental Science and Pollution Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Carbon capture, Ladle refining slag, Binder, Carbonation reaction, High strength, Dicalcium silicate, mechanism","lastPublishedDoi":"10.21203/rs.3.rs-3621729/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3621729/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eLadle refining slag (LFS), classified as solid waste, presents an imminent need for comprehensive utilization. Notably, LFS contains a substantial amount of γ-Ca\u003csub\u003e2\u003c/sub\u003eSiO\u003csub\u003e4\u003c/sub\u003e (γ-C\u003csub\u003e2\u003c/sub\u003eS) with remarkable carbonation potential, making it an ideal candidate for the production of carbonated cement through Carbon Capture and Storage (CCS) technology. This study delves into the carbonation reaction of the cast and molded lump LFS within a CO\u003csub\u003e2\u003c/sub\u003e pressure vessel. It systematically examines the influence of water-solid ratio and water content on the initial properties of specimens. Furthermore, the investigation encompasses the impact of temperature, reaction time, and CO\u003csub\u003e2\u003c/sub\u003e pressure on carbonation processes and resultant products, contributing to the formulation of a carbonation reaction and mass-transfer mechanism. The research reveals pivotal findings: lower water-solid ratios lead to denser specimens with higher strength, and an optimal 7% water content facilitates effective cementation and reactant dissolution. The controlled growth of densely layered calcite at 20\u0026deg;C yields impressive strengths of up to 120.5MPa, while elevated temperatures, such as 60\u0026deg;C, encourage the growth of smaller calcium carbonate crystals, resulting in a favorable carbon sequestration rate of 19.72%. Extending the carbonation time enhances the conversion rate of γ-C\u003csub\u003e2\u003c/sub\u003eS to calcium carbonate. Intriguingly, CO\u003csub\u003e2\u003c/sub\u003e pressure exerts minimal influence on the specimens. The research elucidates the five-step carbonation process and its underlying diffusion mechanism. In essence, this study harnesses CCS technology to offer a high-value solution for addressing LFS disposal challenges.\u003c/p\u003e","manuscriptTitle":"Study on preparation and CO2 sequestration mechanism of high-strength carbonated Ladle refining slag binder","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-01-01 09:12:21","doi":"10.21203/rs.3.rs-3621729/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major Revision","date":"2024-04-15T14:28:26+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2023-12-27T19:50:06+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2023-12-27T16:02:53+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Environmental Science and Pollution Research","date":"2023-12-22T14:28:17+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2023-11-27T05:51:25+00:00","index":"","fulltext":""},{"type":"submitted","content":"Environmental Science and Pollution Research","date":"2023-11-21T05:12:33+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"environmental-science-and-pollution-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"espr","sideBox":"Learn more about [Environmental Science and Pollution Research](https://www.springer.com/journal/11356)","snPcode":"11356","submissionUrl":"https://submission.nature.com/new-submission/11356/3","title":"Environmental Science and Pollution Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"eb308fd8-f6ad-4e0e-832e-7b99d561f2d0","owner":[],"postedDate":"January 1st, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"in-revision","subjectAreas":[],"tags":[],"updatedAt":"2024-04-15T18:29:02+00:00","versionOfRecord":[],"versionCreatedAt":"2024-01-01 09:12:21","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3621729","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3621729","identity":"rs-3621729","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}