Due to its low hydraulic reactivity, ladle slag is currently underutilized with nearly 80% of annual generation is either landfilled or dumped. This work investigates the joint activation of LS with ...Class F fly ash, and the impact of ladle slag on fly ash geopolymer with the focus on activation, hydrates assemblage, conversion process, and thermal behavior. Results reveal that the unique reaction process of ladle slag in alkali activation system shows a positive influence on fly ash geopolymers. Within an alkaline system rich in soluble Si, the initially hydrated CAH phases transform into C-A-S-H, which not only hinders the conversion and enhances the mechanical strength but also retains the geopolymerization. The hybrid geopolymer system exhibits superior thermal performance to pure fly ash geopolymers, especially under high temperature exposure. With increasing ladle slag substitution, more stable crystalline phases are formed at high temperatures. After 800 °C exposure, a high residual compressive strength of 64.7 MPa is achieved with 25 wt% ladle slag addition compared to 55.2 MPa in pure fly ash geopolymers.
The gel compatibility in calcium contained geopolymers remains a controversial topic. This work aims to clarify the role of Ca availability in determining the geopolymerization of alkali-activated ...ladle slag/Class F fly ash blends. The results show that the product layer wrapping around slag particles largely governs the Ca diffusion into the environment, enabling the development of two separated gels, namely C-(N)-A-(S)-H and N-(C)-A-S-H type gel. A dense matrix consisting of geopolymer gel and Ca-enriched gel is achieved with 8 % of Na2O while increasing Ms. intensifies the incompatibility between two gels, leading to microcrack formation and lowered mechanical strength. The competition between different reaction mechanisms of the two gels predominates the initial properties and thermal performance of the hybrid binder. A thermal degradation model of hybrid geopolymer co-existing geopolymeric gel and Ca-enriched gel is proposed to describe the influence of gel compatibility on the thermal behavior of Ca incorporated geopolymer.
Ladle slag is a by-product of secondary steel treatment. A typical management option for ladle slag is stockpiling in open yards. Given the massive production quantities of such material, this ...disposal mechanism has posed major environmental concerns over the years. The construction industry is a potential area that may recycle ladle slag as a sustainable replacement to cement binder, thereby reducing the consumption of cement, conserving natural resources, and alleviating greenhouse gas emissions. Accordingly, this paper provides a state-of-the-art review of the generation, characteristics, and reaction mechanisms of ladle slag. The effect of utilizing ladle slag on the fresh and hardened properties and microstructure of alkali-activated mortar and cement-based conventional and self-compacting concrete is also reviewed. Findings highlighted that utilizing ladle slag by the concrete industry is possible with favorable properties when certain preprocessing measurements, such as milling, sieving, and gypsum addition, are implemented. Furthermore, it is concluded that the degree of reaction and performance of alkali-activated mortar and concrete are dependent on the curing temperature and the type and components of the alkaline activator solution. Also, the replacement of 20% cement with ladle slag does not compromise the strength and durability aspects of cement-based concrete. From an environmental perspective, ladle slag is considered a non-hazardous material suitable for use in construction applications. The research gaps in the existing knowledge and future research directions are also identified.
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•Generation, characteristics, and reactivity of ladle slag are summarized.•Various utilization schemes for ladle slag as a construction material are reviewed.•Environmental impact of using ladle slag in mortar and concrete is discussed.•Research gaps in the existing knowledge and future research directions are highlighted.
Global sustainable development faces challenges in greenhouse gas emissions, consumption of energy and non-renewable resources, environmental pollution, and waste landfilling. Current technologies ...for immobilization of heavy metals face similar challenges; for example, the use of cement, magnesia, lime, and other binders for immobilization of heavy metals is associated with carbon dioxide emission and consumption of limestone/magnesite and energy. In these contexts, this study introduced a novel and sustainable method for immobilization of lead (Pb) by using an industrial solid waste (ladle furnace slag, LFS) and a greenhouse gas (carbon dioxide). In this laboratory investigation, LFS was first mixed with the lead nitrate and then treated by conventional curing (without carbon dioxide) and carbonation curing (with carbon dioxide) for different periods. The treated LFS were then analyzed by various chemical analyses and microanalysis. The results showed that LFS with conventional curing is not effective in immobilization of lead, while LFS with carbonation curing can effectively immobilize lead. The leaching concentrations of Pb from carbonated LFS were four orders of magnitude lower than those with conventional curing. LFS can achieve carbon dioxide uptake of up to 8% of LFS mass. During the carbonation process, carbonates were produced and wrapped LFS particles to prevent the release of lead, lead nitrate was also carbonated into lead carbonate, and the pH of LFS was reduced to 9.36–9.58, close to the minimum solubility of lead carbonate; these are the main reasons for lead immobilization. In summary, the use of LFS with carbon dioxide for immobilization of lead can not only sequester carbon dioxide, but also reduce the cost of binders, non-renewable resource consumption, energy use, and LFS landfilling.
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•Lead (Pb) is immobilized by ladle furnace slag (LFS) and CO2.•CO2 is sequestered and stored.•Binder cost for Pb immobilization is reduced.•LFS landfilling is reduced.•Consumption of non-renewable resources and energy are reduced.
•Taguchi L16 matrix was used to design the experiments with five factors and four levels.•TOPSIS method was used to optimize alkali-activated ladle slag mortar constituents.•Four quality ...characteristics were used in the multi-criteria optimization method.•Taguchi-TOPSIS integration can optimize alkali-activated ladle slag mortar mix design.•Optimum mix compressive strength, workability, and initial setting time were 17.9 MPa, 177.5 mm, and 13 min.
This study examines the effect of various parameters on the properties of alkali-activated composites made with unprocessed ladle furnace slag. Taguchi method was used to design the experiments. A total of five factors, each with four levels, were considered, including ladle slag content (LS), alkaline-activator solution-to-binder ratio (AAS/B), sodium silicate-to-sodium hydroxide ratio (SS/SH), sodium hydroxide molarity (M), and crushed sand replacement by dune sand (CSR). A total of 16 alkali-activated ladle slag mixtures were designed, cast, and tested. The performance responses were the workability, setting time, and compressive strength. To assess the influence of the factors on the responses, Taguchi analysis and ANOVA were employed while determining the signal-to-noise (S/N) ratios. Further, TOPSIS analysis was carried out to optimize the mixture proportions of alkali-activated ladle slag composites. The optimum mix entailed 650 kg/m3 of ladle slag, AAS/B ratio of 0.45, SS/SH of 2, and CSR of 25% to maximize strength and workability. Meanwhile, the optimum mix to maximize workability and setting time included 650 kg/m3 of ladle slag content, AAS/B ratio of 0.6, SS/SH of 2.5, and CSR of 50%. Anticipated results of the optimum mixes were experimentally verified. Microstructure analysis of the optimum mixes (isothermal calorimetry, Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy) highlighted the accelerated rate of the activation reaction, the amorphous morphology, and the formation of calcium aluminosilicate hydrate gel.
Fe-rich alkali activated materials (AAMs) require detailed understanding of their durability prior to their real-life application in the construction industry. Three mixes were formulated with ...fayalite slag (FS) as the main precursor. The effect of incorporation of ladle slag (LS) or blast furnace slag (BFS) on the shrinkage and exposure to physical and chemical attacks representing environmental conditions in cold and tropical regions (acidic solution at room temperature and in freeze-thaw, combined sodium sulfate and sodium chloride solution at room temperature and in freeze-thaw, freeze-thaw in water and dry-wet cycles) was investigated via visual observation, mass loss, compressive strength, X-ray diffraction (XRD), mercury intrusion porosimetry (MIP), and scanning electron microscope coupled with energy dispersive X-ray spectroscopy (SEM-EDS). Experimental results show the considerable role of incorporated LS and BFS in modifying the gels formed and controlling material degradation of blended AAMs after exposure. In contrast, sole FS-based samples were completely degraded particularly those exposed to freeze-thaw in water, acid, and combined sodium sulfate and sodium chloride solution, indicating their vulnerability to frost and chemical attacks.
•Durability of Fe-rich alkali-activated materials (AAMs) exposed to different environmental conditions was elucidated.•Sole fayalite slag-based AAMs were completely degraded during exposure to freeze-thaw in water, acid and combined sodium sulfate and chloride•Incorporation of ladle slag (LS) or blast furnace slag (BFS) helps to control AAMs degradation during exposure to aggressive environments.•AAMs containing LS or BFS exhibited better mechanical, microstructural and durability properties after exposure.•Deterioration of AAMs was caused by water and chemical uptake in the pores.
Alkali activated materials (AAMs), a potential alternative to cement-based products or ceramics, can incorporate large amounts of currently landfilled aluminosilicate rich materials such as calcined ...clay-rich river sediments collected at hydropower plant dams. Untreated fresh sediment and untreated aged sediment intended to serve as AAM precursors were calcined to increase their amorphous content, then activated by Na or K-based silicate or hydroxide solutions and cured at 60 °C for three days.
Up to 30 mass % (ma%) of fly ash (FA) or ladle slag (LS) increased the mechanical performance. The phase composition and microstructure are analyzed using X-ray diffraction, fourier-transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and mercury intrusion porosimetry to gain further insight into how the additives influence the final properties of the resulting AAMs. The main crystalline components of the prepared AAMs are quartz, illite/muscovite and feldspar. The amorphous content reaches up to 52.5 ma% in the Na-activated AAMs and up to 48.8 ma% in K-activated AAMs. The acquired results confirm the suitability of the investigated sediments as sole precursors for AAMs. The mechanical properties of the AAMs can be improved by adding FA and/or LS.
•Clay-rich river sediments were calcined to increase their reactivity to be used as alkali activated (AA) precursors.•AA materials based on sediments were successfully prepared by Na- or K-based activators.•By addition of fly ash or ladle slag mechanical properties of the resulting AAMs are further improved by about 50%.•The compressive strength increase can be correlated to an increased amorphous content and solubility in alkaline media.
The disposal of ladle furnace slag (ladle slag, LS) containing traces of heavy metals produced during steelmaking has become an environmental issue. The use of LS as a binding material in civil ...engineering is a potential solution. In this context, this study firstly attempted to activate LS with sodium hydroxide (NaOH), sodium sulfate (Na2SO4), and sodium metasilicate (Na2SiO3), and then blended it with ground granulated blast-furnace slag (GGBS) with different LS:GGBS ratios. The chemical-activated LS pastes and LS-GGBS pastes were cured for different ages, and then subjected to a compressive strength test. The results indicated NaOH, Na2SO4, and Na2SiO3 could not effectively activate this LS, with 28-day strength <2 MPa, whilst the LS-GGBS yielded much higher strength, up to 15.6 MPa at 28 days. Only a very low concentration of Pb leached out from the LS-GGBS at 14 days, and none of the possible heavy metals were detected at 56 days. This indicates that LS-GGBS can be potentially used as a binding material in civil engineering. The X-ray diffraction (XRD) revealed that the Ca(OH)2 in LS acted as the main activator for GGBS hydration; the MgO and CaCO3 in LS seemed to play similar roles as that of the Ca(OH)2. The XRD, thermogravimetric analysis (TGA), fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), and energy dispersive X-ray spectroscopy (EDX) indicated that the main hydration product of LS-GGBS was calcium silicate hydrates (CSH).
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•NaOH, Na2SO4, and Na2SiO3 are not effective to activate ladle slag.•LS activates ground granulated blast-furnace slag (GGBS) effectively.•Ca(OH)2 in LS accelerates strength development of GGBS.•Hydration products of LS-GGBS immobilize heavy metals in LS.
A proper and detailed understanding of the thermal stability of Fe-rich fayalite slag-based alkali-activated materials (AAMs) is important due to their potential use in refractory and fire-resistant ...applications. Here, fayalite slag (FS) was used as the main precursor for AAMs. The effects of incorporating ladle slag (LS) or blast furnace slag (BFS) and different temperature exposures up to 1000 °C were investigated through visual observation, compressive strength, ultrasonic pulse velocity (UPV), thermal conductivity, x-ray diffraction (XRD), thermogravimetry and differential scanning calorimetry (TG/DSC), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope coupled with electron probe microanalyzer (SEM-EPMA). The experimental results indicated that the incorporation of LS or BFS as additional calcium and aluminum sources positively affected the high-temperature behavior of blended mortars, which exhibited a reduction in voids, cracks, and thermal shrinkage while having higher residual strength and thermal stability than solely FS-based AAMs. This was mainly due to the differences in mineralogical transformation and the phases formed. Interestingly, the joint effect of elevated temperature exposure and the addition of LS or BFS enhanced the formation of more stable crystalline phases and densified the structure of blended mortars at 1000 °C.
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•Upcycling of Fe-rich fayalite slag as refractory and fire-resistant alkali-activated materials (AAMs) was elucidated.•Ladle slag (LS) or blast furnace slag (BFS) addition improved AAMs properties during ambient and high temperature exposure.•AAMs containing LS or BFS have better mechanical, thermal, and microstructural properties.•Joint effect of elevated temperature and LS or BFS addition favored more stable crystalline phase formation and densification.•The results provided an insight for designing eco-friendly refractory materials for building and construction industry.
•CO2 is fast sequestered and chemically stored in ladle slag (LS).•Zn is fast and effectively immobilized by LS and CO2.•LS landfilling, consumption of non-renewable resources and energy are reduced.
...Environmental pollution, waste management, and greenhouse gas emissions pose significant challenges to global sustainable development. To address these challenges, this study introduces an innovative approach by reusing an industrial waste, ladle slag (LS), and greenhouse gas, CO2, for fast immobilization of zinc. In this study, specimens were prepared by mixing LS with zinc nitrate with initial concentrations of 0–25,000 mg/kg and then subjected to conventional and CO2 curing. Leaching test and chemical analysis tests were also conducted. The results showed that LS with CO2 requires only 112 hours to achieve around 2–3 times lower leaching concentrations than that of conventional curing for 28 days, being around 1–2 orders of magnitude lower than that without CO2 and conventional curing. Simultaneously, CO2 up to 13.5 % of LS mass was also sequestered. This approach provides a triple benefit by simultaneously immobilizing zinc, mitigating LS landfilling, and capturing CO2.
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