Mineral phases and carbon content in weathered fly ashes

Wirth, Xenia; Glatstein, Daniel Alejandro; Burns, Susan E.

doi:10.1016/j.fuel.2018.09.106

Cited by 22 publications

(19 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…By contrast with the morphology of commercial fly ash, which consists of spherical and vitreous particles [41], particles with an irregular shape and rough surface were also found in LFA, and the size ranged from 1 µm to 40 µm, and coarse agglomerates with depositional bonding structure in the appearance of long "threads" can be observed in Figure 12a. This agrees with the description in [11]. It was caused by the weathering effect during the land filled period.…”

Section: Scanning Electron Microscopy (Sem) Analysissupporting

confidence: 92%

“…Meanwhile, long-term weathering causes transformation in the physical and chemical composition [ 8 , 9 ]. Reactive components leach out and the hydraulic potential of landfilled fly ash (LFA) is much lower than that of conventional fly ash, which is usually not suitable to be used in the cement and concrete industry [ 10 , 11 ]. Therefore, more effective technology is demanded to reduce the landfilling as well as to reduce the greenhouse gases [ 9 ].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Setting and Hardening Behaviour of Alkali-Activated Landfilled Fly Ash–Slag Binder at Room Temperature

et al. 2020

View full text Add to dashboard Cite

A geopolymer is normally considered an environmentally friendly binder due to the utilisation of industrial wastes. This study focusses on the potential of geopolymer preparation at room temperature from landfilled fly ash (LFA) which has been discharged to the land for more than three years. To accelerate the reaction process, 20–30 wt.% LFA was replaced by ground-granulated blast-furnace slag (GGBS). The effect of water glass modulus, Na2O content, water-to-solid ratio, and GGBS content on the setting time and strength development of the binder was discussed. Results showed that to activate LFA, the optimal value of the sodium silicate modulus for alkaline solution was 1.4–1.6 with a Na2O content of 10%, and the water-to-solid ratio was 0.4. In addition, the setting time of the binder reduced with increasing content of GGBS replacement, and the compressive strength increased due to the coexistence of C-(A)-S-H and zeolite-like phases. The maximum compressive strength of the binder was 29.2 MPa after 56 days of curing. The relatively low strength was likely due to the absence of the Q4 unit with a three-dimensional structure.

show abstract

Section: Scanning Electron Microscopy (Sem) Analysissupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Setting and Hardening Behaviour of Alkali-Activated Landfilled Fly Ash–Slag Binder at Room Temperature

et al. 2020

View full text Add to dashboard Cite

show abstract

“…50 This hydration has two major effects: (1) new mineral phases develop, including carbonates and amorphous clays (from glass hydrolysis) and (2) alkaline metals are leached. 50 Thus, weathered CFAs may contain lower quantities of potentially interfering elements and present higher REE concentrations in more accessible mineral forms. 50 In this study, the REE content of CFA-F2 was slightly less than that of CFA-F1.…”

Section: Resultsmentioning

confidence: 99%

“…50 Thus, weathered CFAs may contain lower quantities of potentially interfering elements and present higher REE concentrations in more accessible mineral forms. 50 In this study, the REE content of CFA-F2 was slightly less than that of CFA-F1.…”

Section: Resultsmentioning

confidence: 99%

Preferential Recovery of Rare-Earth Elements from Coal Fly Ash Using a Recyclable Ionic Liquid

Stoy

Díaz

Huang

2021

Environ. Sci. Technol.

View full text Add to dashboard Cite

Recent global geopolitical tensions have exacerbated the scarcity of rare-earth elements (REEs), which are critical across many industries. REE-rich coal fly ash (CFA), a coal combustion residual, has been proposed as a potential source. Conventional REE-CFA recovery methods are energy-and materialintensive and leach elements indiscriminately. This study has developed a new valorization process based on the ionic liquid (IL) betainium bis-(trifluoromethylsulfonyl)imide ([Hbet][Tf 2 N]) for preferential extraction of REEs from different CFAs. Efficient extraction relies on [Hbet][Tf 2 N]'s thermomorphic behavior with water: upon heating, water and the IL form a single liquid phase, and REEs are leached from CFA via a proton-exchange mechanism.Upon cooling, the water and IL separate, and leached elements partition between the two phases. REEs were preferentially extracted over bulk elements from CFAs into the IL phase and then recovered in a subsequent mild-acid stripping step, regenerating the IL. Alkaline pretreatment significantly improved REE leaching efficiency from recalcitrant Class-F CFAs, and additional betaine improved REE and bulk element separation. Weathered CFA showed slightly higher REE leaching efficiency than unweathered CFA, and Class-C CFA demonstrated higher leaching efficiency but less selective partitioning than Class-F CFAs. Significantly, this method consistently exhibits a particularly high extraction efficiency for scandium across different CFAs.

show abstract

“…Wirth et al [76] examined changes in fly ash with weathering and found the presence of hydrated phases in some cases, including calcium sulfates, carbonates and clays, suggesting that compositional changes may occur and should be examined. They also found changes in particle morphology with weathering.…”

Section: By-product Materials: Ashes and Glassmentioning

confidence: 99%

Supplementary cementitious materials: New sources, characterization, and performance insights

Juenger

Snellings

Bernal

2019

Cement and Concrete Research

730

171

View full text Add to dashboard Cite

Conventional supplementary cementitious materials (SCMs), such as blast furnace slags or fly ashes, have been used for many decades, and a large body of knowledge has been collected regarding their compositional make-up and their impacts on cement hydration and concrete properties. This accumulated empirical experience can provide a solid, confident base to go beyond the status quo and develop a new generation of low-clinker cements composed of new types and combinations of SCMs.The need for new sources of SCMs has never been greater, as supplies of traditional SCMs are becoming restricted, and the demand for SCMs to reduce CO2 emissions from concrete production is increasing. In this paper, recent research on emerging SCM sources is reviewed, along with new developments in characterizing and qualifying SCMs for use and improved knowledge of SCMs on long-term concrete performance and durability. Keywords(B) Characterization; (C) Durability; (D) Blended Cement; (D) Filler; (D) Pozzolan Material Chemistry Used as SCM (Mt/y)Total volume est. (Mt/y) Comments Blast furnace slag Ca-Si-Al 330 300-360 Nearly fully used, latent hydraulic Coal fly ash Si-Al 330-400 700-1100 Subject to limitations on carbon content, reactivity Natural pozzolans Si-Al 75 Large accessible reserves Large variety/variability, often high water demand Silica fume Si 0.5-1 1-2.5 Used in high-performance concrete Calcined clays Si-Al 3 Large accessible reserves Metakaolin performs best, often high water demand Limestone CaCO3 300 Large accessible reserves Cementitious contribution in combination with reactive aluminates Biomass ash Si 0 100-140 Competition with use as soil amendment, high water demand, (for some: high alkali contents) MSWI bottom ash Si-Al-Ca 0 30-60 Expansive and corrosive components, leaching issues Steel slag Ca-Si-Fe 0 (negligible) 170-250 Various types, can contain expansive components (CaO) or leachable heavy C L reactivity Copper slag Fe-Si 0 (some as filler) 30-40 Low reactivity, leaching of heavy metals, more research needed Other non-ferro slags Fe-(Si)-(Ca) 0 (some as filler) 5-15 Mt/y each (FeCr, Pb, Ni) Low reactivity, leaching of heavy metals, more research needed

show abstract

Mineral phases and carbon content in weathered fly ashes

Cited by 22 publications

References 30 publications

Setting and Hardening Behaviour of Alkali-Activated Landfilled Fly Ash–Slag Binder at Room Temperature

Setting and Hardening Behaviour of Alkali-Activated Landfilled Fly Ash–Slag Binder at Room Temperature

Preferential Recovery of Rare-Earth Elements from Coal Fly Ash Using a Recyclable Ionic Liquid

Supplementary cementitious materials: New sources, characterization, and performance insights

Contact Info

Product

Resources

About