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.
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.
Steel slag is a by-product of steelmaking which has emerged as a potential CO2 sequestration material due to its high reactivity and abundance. This research investigates the use of steel slag waste ...for the direct capture of carbon from air and its storage through mineral carbonation. Two abundant wastes, blast-furnace slag (BFS) and ladle slag (LS), were tested for their carbon sequestration potential, and the effects of operational parameters such as reaction time between CO2 and slag waste, temperature, liquid-solid ratio, and pressure on CO2 sequestration were determined.
Quantitative and qualitative results reveal that much higher CO2 sequestration was achieved using LS compared to BFS after exposure to CO2 for 1 day at room temperature. By increasing the exposure time to four days, levels of CO2 sequestration increased gradually from 2.71% to 4.19% and 23.46%–28.21% for BFS and LS respectively. Increasing the temperature from 20 ± 2 °C to 90 ± 2 °C positively influenced CO2 sequestration in BFS, resulting in an enhancement from 3.45% to 13.21%. However, the impact on LS was insignificant, with sequestration levels rising from 27.72% to 29.90%. Moreover, better CO2 sequestration was observed for BFS than LS when the liquid-to-solid ratio increased from 3:1 to 4:1, whereupon the sequestration potential reached approximately 15% for BFS and 30% for LS at 90 ± 2 °C. Meanwhile, higher pressure reduced the sequestration potential of slag. The results of this study suggest that there is potential for scaling up the process to industrial applications and contributing to the reduction of CO2 emissions in the steelmaking industry.
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•The use of BFS and LS as potential waste materials for carbon capture and storage.•Effect of time, temperature, liquid-solid ratio, and pressure on steel-slags’ carbonation.•Increasing time and temperature improved CO2 sequestration, particularly for BFS.•The negative impact of a higher liquid-solid ratio and pressure on CO2 uptake.•LS achieved twice as much CO2 sequestration as BFS.
The structure-viscosity relationship of the low-silica (SiO2 ≤ 10 wt%) calcium aluminosilicate melts, which represent the secondary refining ladle slag systems, was investigated by employing the ...rotating-cylinder viscosity measurement in conjunction with the Raman spectroscopy measurement for linking the macroscopic thermophysical property and molecular (ionic) structural information. Furthermore, the influence of CaF2 on the structure-property relationship was explored. The viscosity of low-silica calcium aluminosilicate melts decreased with increasing both CaO/Al2O3 and CaO/SiO2 ratios. However, the effect of the former on the viscosity of low-silica calcium aluminosilicate melts was larger than that of the latter. By employing the Neuville’s structure model, in which the silicate structural units with various NBO, i.e. QnSi are located at the boundary of the AlO4 aluminate, and the Raman scattering data of the glass samples, it was demonstrated that the aluminate and silicate units are more effectively modified by increasing the CaO/Al2O3 ratio at fixed silica content. The addition of small amounts of CaF2 (~5 wt%) to the low-silica calcium aluminosilicate melts decreased the viscosity of the melts. From the analysis of Raman scattering data, the liberation of SiO44– (Q0Si) units from the AlO4 aluminate structure by addition of CaF2 was understood. However, the effect of CaF2 addition on the viscosity became less discernible at higher CaF2 content (≥ 10 wt%) region, where the F ions simply substitute for the non-bridging oxygen ions in AlO4 tetrahedra.
Corrosion behaviors and corroded microstructures of MgAl2O4-CaAl4O7-CaAl12O19 composites containing various additives (ZrO2 and TiO2) against steel ladle slag (containing CaF2) were investigated ...using a reaction test method at 1600°C. Thermodynamic calculation, based on the Al2O3–CaO–MgO phase equilibrium diagram was used to further reveal the corrosion mechanism. The attack of the liquid slag on the composite substrate was found to take place through an interdiffusion mechanism, producing the precipitation of spinel in the slag and a continuous layer of calcium dialuminate at the interface. This composite showed a high total corrosion depth due to the high porosity of the substrate and the high fluidity of the slag. Fortunately, the addition of ZrO2 and TiO2 can greatly improve the slag corrosion resistance by increasing the viscosity of the slag at an earlier stage. Besides, the highly dense microstructures also improved the corrosion resistance against the liquid slag, and thus suppressed the slag penetration. It was also found that the CA6 grains with low aspect ratios are more difficult to be wetted and dissolved by the slag.
Aiming to utilize phosphogypsum (PG) as a construction material, this study investigated the potential use of PG as a calcium sulfate source for the production of an ettringite-based binder (LSG). ...Six compositions with different percentages and PG's of different origin were hydrated with ladle slag (LS) to form LSG. The hydration, mineralogy and compressive strength of all mixtures were investigated and compared with a reference LSG made of pure synthetic gypsum. The minor impurities in PG, the different particle size distribution as well as the mineralogy induced distinguishable effects on the heat of hydration, phase assemblage and morphology. The results showed that the use of side-stream PG instead of pure gypsum results in superior properties with a 60% increase in compressive strength. This investigation shows high potential to produce a completely by-product-based LSG by combining different sources of industrial side-streams with minimal chemical and energy use.
•Various sources of phosphogypsum were incorporated in an ettringite-based binder.•The impurities in phosphogypsum delayed the setting of the developed binders.•Polish phosphogypsum led to an increase of 60% in compressive strength.•Ettringite-based binders can be produced entirely from industrial side-streams.
Ladle furnace basic slag (ladle slag, LS) is a by-product of the steel refining process. There is a great amount of LS generated worldwide every year and the current solution is simply landfilling ...it, which causes both economic and environmental issues. This study attempts to use LS to activate ground granulated blastfurnace slag (GGBS) for stabilization of soft clay, as well as immobilization of heavy metals in LS. The LS-GGBS-stabilized clays with different binder contents and LS:GGBS ratios were cured for different periods, and then subjected to unconfined compressive strength (UCS) test, leaching test, and X-ray diffraction (XRD). The results indicated that the LS-GGBS-stabilized clays with LS:GGBS ratio of 2:8–5:5 could achieve similar or higher UCS compared to ordinary Portland cement-stabilized clay after 56 days of curing. The leaching of potential heavy metals was not detected for the LS-GGBS stabilized clays. According to XRD analysis, the main hydration products of LS-GGBS-stabilized clay were calcium silicate hydrates (CSH) and ettringite, which were responsible for the strength development of LS-GGBS-stabilized clays.
•Ladle slag (LS)-ground granulated blastfurnace slag (GGBS) for clay stabilization.•Ca(OH)2 in LS activates GGBS for strength gain.•Heavy metals in LS are immobilized in stabilized clay.
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•An ettringite-based binder from the hydration between ladle slag with gypsum was developed.•The mineralogy of the binder was investigated and compared with a hydrated ladle slag ...binder.•The binder has good mechanical properties and excellent freeze-thaw resistance.
Ladle slag (LS) is a byproduct from the steel industry that is usually reactive on its own and hydrates towards cementitious phases when mixed with water. However, these reaction products are often metastable, leading to micro-structural changes between 7 and 30 days after mixing. To address this issue, in this experimental investigation, a new binder was designed where LS was mixed with gypsum in order to deliver an ettringite-based binder (LSG). The experimental results revealed that the dominant crystalline phase of LSG was ettringite, which remained stable with no conversion at later stages. For better understanding of the ettringite-based binder, mortar characterization, mechanical properties, and durability of LSG were investigated. LSG showed good mechanical properties and excellent freeze-thaw resistance after 300 cycles, which is comparable to other calcium sulfoaluminate cements. Therefore, as a result, the byproduct-based ettringite binder synthesized herein could offer a solution to steelmaking byproducts with a low-CO2 binder, which could be used in a wide range of applications in the construction industry.
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•Variations in chemical composition have an effect on the slag mineralogy.•The leaching of ladle slag is governed by surface phenomena.•Variations in cooling treatment and steel type ...have a small effect on leachability.•The solubility-controlling minerals were predicted by geochemical modelling.•Mineralogical identification of the solubility-controlling minerals (Ca(OH)2, CSH).
In this study, the leachability of freshly produced ladle slag derived from both austenitic and ferritic stainless steel production, and from electrical and structural steel production, was investigated, in order to determine whether variations in the chemical and mineralogical composition of these slags affect their leaching behaviour. The effect of the method used for slag cooling was also studied. The results obtained by using the single batch test were combined with those obtained by means of more sophisticated characterisation leaching tests, which, in combination with geochemical speciation modelling, helped to better identify the release mechanisms and phases that control the release of individual elements. It was found that, although variations in the chemical composition of the slag can affect the slag's minerology, neither such variations, nor the choice of the slag cooling treatment, have a significant effect on the leachability of individual elements, since the leaching is governed by surface phenomena. In fact, the mineral transformations on the slag surface, rather than the bulk mineral composition, dictate the release of these elements from the ladle slag. The solubility-controlling phases were predicted by multi-element modelling, and verified to the extent made possible by the performed mineralogical investigations.
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