Fe(III) uptake by calcium silicate hydrates

Mancini, A.; Wieland, Erich; Geng, Guoqing; Dähn, Rainer; Wehrli, Bernhard; Lothenbach, Barbara

doi:10.1016/j.apgeochem.2019.104460

Cited by 38 publications

(33 citation statements)

References 80 publications

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“…The K d values of ≈ 600 m 3 /kg for Al in the absence of alkali are comparable to the K d values of ≈ 700 m 3 /kg for Fe(III) on C–S–H reported in [ 76 ]. However, they are considerably higher than the K d values in the range of 0.1 m 3 /kg to 6 m 3 /kg observed for bivalent cations such as Fe(II), Ba(II) or Sr(II) [ 78 – 80 ].…”

Section: Resultssupporting

confidence: 86%

“…The decrease of Al uptake by C-S–H with increasing the pH value (Fig. 11 ) is comparable to the decrease of Fe(III) uptake by titanium dioxide (TiO 2 ) with increasing the pH value [ 76 ], which is present mainly as negatively charged hydroxide complex (Fe(OH) 4 − ) at pH values above 10. The aqueous aluminum speciation depends on pH; negatively charged Al(OH) 4 − dominates at pH > 7 as explained in [ 35 , 77 ].…”

Section: Resultsmentioning

confidence: 52%

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A long-term study on structural changes in calcium aluminate silicate hydrates

et al. 2022

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Production of blended cements in which Portland cement is combined with supplementary cementitious materials (SCM) is an effective strategy for reducing the CO2 emissions during cement manufacturing and achieving sustainable concrete production. However, the high Al2O3 and SiO2 contents of SCM change the chemical composition of the main hydration product, calcium aluminate silicate hydrate (C–A–S–H). Herein, spectroscopic and structural data for C–A–S–H gels are reported in a large range of equilibration times from 3 months up to 2 years and Al/Si molar ratios from 0.001 to 0.2. The 27Al MAS NMR spectroscopy and thermogravimetric analysis indicate that in addition to the C–A–S–H phase, secondary phases such as strätlingite, katoite, Al(OH)3 and calcium aluminate hydrate are present at Al/Si ≥ 0.03 limiting the uptake of Al in C–A–S–H. More secondary phases are present at higher Al concentrations; their content decreases with equilibration time while more Al is taken up in the C–A–S–H phase. At low Al contents, Al concentrations decrease strongly with time indicating a slow equilibration, in contrast to high Al contents where a clear change in Al concentrations over time was not observed indicating that the equilibrium has been reached faster. The 27Al NMR studies show that tetrahedrally coordinated Al is incorporated in C–A–S–H and its amount increases with the amount of Al present in the solution.

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Section: Resultssupporting

confidence: 86%

Section: Resultsmentioning

confidence: 52%

A long-term study on structural changes in calcium aluminate silicate hydrates

et al. 2022

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“…In these experiments, the precipitation of Fe(OH) 3 (s) is commonly observed in addition to Fe(III)-containing hydrate phases, such as hydrogarnet 1 [36] and carbonate containing AFm phases [37,38]. This observation underlines that the sparingly soluble Fe(OH) 3 (s) marks the upper solubility limit for Fe(III) in cementitious systems [46,47].…”

Section: Review Of Empirical Data On Iron Phases In Cementitious Systemsmentioning

confidence: 77%

“…It can also exist as ferrihydrite (Fe(OH) 3 (s)) during the first hours of hydration or bind to siliceous hydrogarnet (C 3 (A,F)S y H 6− 2y and C 3 FS y H 6− 2y ) at longer hydration times [42]. In addition, some Fe(III) might also be present in the form of Fe-hydrotalcite (M 3 F 0.5 c 0.5 H 6 ), partially replace Al(III) in ettringite (Ca 6 [Al 1− x Fe x (OH) 6 ] 2 (SO 4 ) 3 ⋅26H 2 O) and/or monosulfate (Ca 4 [Al 1− x Fe x (OH) 6 ] 2 (SO 4 )⋅6H 2 O), or be taken up both by C-S-H in the form of Fe(II) or Fe(III) [32,36,37,42,47,79,80]. The ferrihydrite formation during the first hours of hydration [42] indicates the importance of 2-line ferrihydrite (2l-Fe(OH) 3 (s)) as a solubility limiting iron bearing phase in accordance with a maximum aqueous iron concentration at early hydration times [35,39,40,42,81].…”

Section: Iron-bearing Cementitious Phasesmentioning

confidence: 99%

Solubility and speciation of iron in cementitious systems

Furcas

Lothenbach

Isgor

et al. 2022

Cement and Concrete Research

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Aqueous iron hydrolysis products and chloride complexes influence steel corrosion kinetics and dictate the amount and type of corrosion products formed. Here, we compile a thermodynamic database devoted to aqueous iron species and solid oxides as well as chloride complexes, aiming to describe their speciation and solubility within the prevailing chemical environment of interest for cementitious systems. We compare thermodynamic calculations to empirical data on the elemental composition of pore solutions from cementitious systems.It is found that dissolved iron concentrations in cement pore solutions can differ considerably from thermodynamic predictions. In particular, measured Fe(II) concentrations can exceed the thermodynamic limit by 2-5 orders of magnitude. Additionally, experimentally obtained iron solubility in the presence of chloride exceed thermodynamic predictions. We discuss that these differences may be explained by so far unknown iron complexes, stabilisation of intermediate phases such as chloride green rust, or due to (kinetic) hindrance of precipitation.

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“…Due to this large amount found in the waste, some works are reported in literature trying to recover iron from the bauxite residue [26], [27], but the process is not yet economically viable, and the remaining waste (with a low amount of iron) is still discarded. Other works are purposed to understand the mechanisms of iron interaction with cementitious materials for predicting the service life and design of reinforced concrete structures [28].…”

Section: Materials Characterizationmentioning

confidence: 99%

Combined evaluation of oscillatory rheometry and isothermal calorimetry for the monitoring of hardening stage of Portland cement compositions blended with bauxite residue from Bayer process generated in different sites in Brazil

Romano

Mesquita

Bernardo

et al. 2021

Rev. IBRACON Estrut. Mater.

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Bauxite residue (BR), a by-product of alumina and aluminum production, consists of high aluminum, silica, and iron content, and sodium from the bauxite ore digestion during the Bayer process. This waste is still being disposal into the lakes of mud, causing some environmental problems. So, the search for its application has gained interest. Studies reported in literature point out that one of the most promising applications is in association with Portland cement, which can also help to reduce the environmental impact caused by the CO2-emissions in its production. In this work, a combined evaluation of oscillatory rheometry and isothermal calorimetry was performed for the monitoring of the hardening stage of Portland cement (PC) compositions blended with BR generated in different sites in Brazil. The time-sweep test was applied to obtain the consistency gain of suspensions over-time, allowing us to understand the physical parameters of consolidation, while the changes in the hydration reaction showed considerable differences in the chemical contribution. As a conclusion, it was clear the impact of each BR, mainly due to the aspects related to soluble aluminates, silicates, and sodium, which in association with the soluble ions from PC, affected the chemical reaction and agglomeration/flocculation forces of particles.

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Fe(III) uptake by calcium silicate hydrates

Cited by 38 publications

References 80 publications

A long-term study on structural changes in calcium aluminate silicate hydrates

A long-term study on structural changes in calcium aluminate silicate hydrates

Solubility and speciation of iron in cementitious systems

Combined evaluation of oscillatory rheometry and isothermal calorimetry for the monitoring of hardening stage of Portland cement compositions blended with bauxite residue from Bayer process generated in different sites in Brazil

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