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Cited by 44Concrete and Cement Materials ResearchCO2 Sequestration and Geologic InteractionsCarbon Dioxide Capture Technologies

Thermodynamic Modeling and Experimental Study of Carbonation of Alkali-Activated Slag Cements

Open access
Park, Solmoi, Lothenbach, Barbara, Jang, Jeong Gook, Kim, Hyeong-Ki, Lee, Namkon·2023·ACS Sustainable Chemistry & Engineering
DOI 10.1021/acssuschemeng.2c05789
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Abstract

The present study investigates the carbonation of slags activated by NaOH, Na 2 SiO 3, Na 2 CO 3, and Na 2 SO 4 . The main hydrates in those activated with NaOH or Na 2 SiO 3 were C-(N-)A-S-H, strätlingite, and MgAl-layered double hydroxide phases as observed using different experimental characterization techniques and thermodynamic modeling. The use of a Na 2 CO 3 activator led to the formation of calcium carbonate and monocarbonate instead of strätlingite, and Na 2 SO 4 to ettringite formation. Carbonation of the alkali-activated slags in a powdered form at 1 vol % concentration of the CO 2 environment proceeded rapidly, while little change was observed after 7 d. The main carbonation products commonly identified were calcium carbonate, carbonate containing-MgAl-layered double hydroxide, and N-A-S-H. In Na 2 SiO 3 - and Na 2 SO 4 -activated slags, M-S-H formation was predicted, which destabilized the MgAl-layered double hydroxide phases. Strätlingite and monocarbonate, which were initially present or formed as a transient phase, were transformed to N-A-S-H during carbonation, while C-(N-)A-S-H was only partially decalcified and destabilized.

Integrity signals

Registry

Crossref · 10.1021/acssuschemeng.2c05789

Cites

67 of 67 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

14 of 32 cited sources checked · 7 supported · 0 flagged · accuracy not yet measured

  • Premisecitation

    The weak resistance of alkali-activated slag against carbonation can be attributed to the absence of portlandite in contrast to hydrated Portland cement.

    “The weak resistance of alkali-activated slag against carbonation can be attributed to the absence of portlandite in contrast to hydrated Portland cement 27,28 .”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [27] source
    • cites [28] source

      The Introduction (p. 5) says accelerated carbonation testing appears much more aggressive toward alkali-activated concrete than toward Portland cement concrete. It does not attribute that difference to an absence of portlandite; the Abstract (p. 2) also cautions that accelerated tests give unrealistically low predictions of in-service carbonation resistance. (LLM, conf=0.84)

      Experimental — accuracy not yet measured
  • Premisecitation

    The CO2 uptake values are comparable or higher than that of hydrated neat and blended Portland cement carbonated in a natural condition for a few years.

    “These values are comparable or higher than that of hydrated neat and blended Portland cement carbonated in a natural condition for a few years 44 .”
    Quote in the paperNot a substantial claim1 of 1 sources checked
  • Findingcitation

    The 27Al NMR spectrum of the NaOH-activated slag before carbonation exhibits resonances at 74 and 9.5 ppm, due to the presence of the Al(IV) sites in C-(N-)A-S-H and Al(VI) in LDH.

    “The 27 Al NMR spectrum of the NaOH-activated slag before carbonation in Figure 5 exhibits resonances at 74 and 9.5 ppm, due to the presence of the Al(IV) sites in C-(N-)A-S-H and Al(VI) in LDH 31 .”
    Quote in the paperNot a substantial claim1 of 1 sources checked
  • Premisecitation

    Hydrotalcite-like LDH is less stable in the presence of sodium silicate.

    “It is known that hydrotalcite-like LDH is less stable in the presence of sodium silicate 23 , thus use of Na2SiO3 as an activator may lead to increasing the carbonation extent.”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [23] source

      Section 3.2 reports that Mg–Al LDH stability fields are similar in the modeled sodium-silicate-activated systems and that precipitation depends only weakly on their bulk SiO₂ content. The passages found do not establish that hydrotalcite-like LDH is less stable in the presence of sodium silicate than in its absence or with another activator; the lower stability discussed in Section 3.3 concerns carbonate-bearing versus carbonate-free LDH. (LLM, conf=0.73)

      Experimental — accuracy not yet measured
  • Findingcitation

    At equal degree of slag reaction, the Na2CO3-activated slag has the highest CO2 binding capacity.

    “If the CO2 binding capacity at equal degree of slag reaction is compared, then the Na2CO3-activated slag has the highest CO2 binding capacity, as shown in 65 .”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [65] source

      The model fixes the degree of slag reaction at 70% (Input parameters, p. 3). It predicts greater CO2 uptake for sodium carbonate-activated than sodium silicate-activated slag while maintaining pore-solution pH above 12.5 (Section 3.2, p. 11). It does not establish the unqualified claim that sodium carbonate-activated slag has the highest CO2 binding capacity among all activators. (LLM, conf=0.86)

      Experimental — accuracy not yet measured
  • May combine two claims. 37
  • The quote only partly states this claim. 1
  • Classified as probably not a substantial claim. 7

  • May combine two claims.

    Premisecitation

    Carbonation is a degradation mechanism that leads to a structural alteration in the hydration products and to which alkali-activated slag is particularly susceptible.

    “Carbonation is a degradation mechanism that leads to a structural alteration in the hydration products and to which alkali-activated slag is particularly susceptible 10 .”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [10] source

      The introduction (p. 4) identifies carbonation of cement hydrates as a degradation mechanism, and the conclusions (p. 20) report structural changes in the hydrate phases of carbonated slag cement. But the paper does not support describing alkali-activated slag generally as particularly susceptible: the conclusions say the sodium carbonate–activated slag cements studied maintained their mechanical strength, unlike some other alkali-activated slag cements. (LLM, conf=0.88)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Premisecitation

    Carbonation neutralizes the pore solution and can lead to corrosion of embedded rebars for concrete; for alkali-activated slags it can cause a reduction in the compressive strength.

    “Carbonation neutralizes the pore solution and can lead to corrosion of embedded rebars for concrete; for alkali-activated slags it can cause a reduction in the compressive strength 10,26 .”
    Quote in the paperSubstantial claim2 of 2 sources checked
    • cites [10] source
    • cites [26] source

      Section 3.2 reports that carbonation reduced the compressive strength of the alkali-activated slag porous concretes. Section 3.3 says carbonation can lower pH, but the passages do not establish that it neutralizes the pore solution or leads to corrosion of embedded rebars. Page numbers are unavailable in our copy. (LLM, conf=0.87)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Premisecitation

    Less is known about slag activated with Na2CO3 and Na2SO4; only a few experimental and modeling studies are available in the literature.

    “Less is known about slag activated with Na2CO3 and Na2SO4; only a few experimental [18][19][20][21][22] and modeling studies 23 are available in the literature.”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [18][19][20][21][22]

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites [23] source

  • May combine two claims.

    Findingcitation

    TGA indicates the presence of C-(N-)A-S-H, with a broad mass loss at approximately 100 °C, and AFm phases such as strätlingite, hemicarbonate, and/or hydrotalcite, as evidenced by the shoulder at 180 °C.

    “TGA indicates the presence of C-(N-)A-S-H, with a broad mass loss at approximately 100 °C, and AFm phases such as strätlingite, hemicarbonate, and/or hydrotalcite, as evidenced by the shoulder at 180 °C 46,47 .”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites [46] source

      The Results and Discussion (p. 9) assign a 165–180 °C peak to monosulfoaluminate hydrate, supporting an AFm-related signal near 180 °C. They do not identify that peak as strätlingite, hemicarbonate, or hydrotalcite. The same section (p. 10) assigns a peak near 100 °C to ettringite, not C-(N-)A-S-H. (LLM, conf=0.86)

      Experimental — accuracy not yet measured
    • cites [47] Lothenbach B., 2016 source

  • May combine two claims.

    Findingcitation

    Strätlingite was not experimentally observed in Na2CO3- and Na2SO4-activated slag, while thermodynamic modeling results indicate that it is a stable phase in both systems.

    “Note that strätlingite was not experimentally observed in Na2CO3- 59 and Na2SO4-activated slag 60 , while thermodynamic modeling results indicate that it is a stable phase in both systems 23,61 .”
    Quote in the paperNot a substantial claim3 of 4 sources checked
    • cites [59] source
    • cites [60] source
    • cites [23] source
    • cites [61] source

  • May combine two claims.

    Findingown data

    Strätlingite and monocarbonate, initially present or formed as a transient phase, were transformed to N-A-S-H during carbonation, while C-(N-)A-S-H was only partially decalcified and destabilized.

    “Strätlingite and monocarbonate, which were initially present or formed as a transient phase, were transformed to N-A-S-H during carbonation, while C-(N-)A-S-H was only partially decalcified and destabilized.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In Na2SiO3- and Na2SO4-activated slags, M-S-H formation was predicted, which destabilized the MgAl-layered double hydroxide phases.

    “In Na2SiO3and Na2SO4-activated slags M-S-H formation was predicted, which destabilized the MgAllayered double hydroxide phases.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Carbonation of alkali-activated slags in powdered form at 1 vol.% CO2 environment proceeded rapidly, with little change observed after 7 d.

    “Carbonation of the alkali-activated slags in a powdered form at 1 vol.%concentration of CO2 environment proceeded rapidly, where little change was observed after 7 d.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning

    The simulated effect of carbonation on the gel chemistry is found to be less apparent, compared to the other two systems discussed above; the Na/Si, Ca/Si and Al/Si ratios of C-(N-)A-S-H changes from 0.33, 0.85 and 0.07 to 0.27, 0.84 and 0.07, respectively, and CO3-LDH remains stable throughout the simulation with its Mg/Al unchanged at 2.0.

    “The simulated effect of carbonation on the gel chemistry is found to be less apparent, compared to the other two systems discussed above; the Na/Si, Ca/Si and Al/Si ratios of C-(N-)A-S-H changes from 0.33, 0.85 and 0.07 to 0.27, 0.84 and 0.07, respectively, and CO3-LDH remains stable throughout the simulation with its Mg/Al unchanged at 2.0.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning

    The thermodynamic calculation predicts gypsum formation instead of bassanite, whereas the experiment found bassanite.

    “The most notable difference between the thermodynamic calculation and the obtained experimental results is that gypsum (CaSO4•2H2O) is predicted to form instead of bassanite (CaSO4•0.5H2O),and ettringite is predicted to be stable even after 90 d of carbonation, which did not occur in the experiment.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingcitation

    The 27Al MAS NMR spectrum of the Na2SO4-activated slag sample before carbonation shows a resonance at 13.5 ppm attributed to ettringite and a resonance at 9.5 ppm attributed to LDH.

    “The 27 Al MAS NMR spectrum of the Na2SO4-activated slag sample before carbonation presented in Figure 21 shows the resonance at 13.5 ppm attributed to the presence of ettringite (marked as AFt in the Figure) 62,63 , and at 9.5 ppm attributed to the presence of LDH.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [62] source
    • cites [63] source

  • May combine two claims.

    Findingown data

    After 7 d of carbonation, reflections due to ettringite are no longer observed in the Na2SO4-activated slag, and bassanite is found along with aragonite as a new carbonation product.

    “After 7 d of carbonation, the reflections due to ettringite are no longer observed, instead, bassanite (CaSO4•0.5H2O,PDF 41-224) is found along with aragonite as a new carbonation product.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    For all samples, regardless of activator, a relatively fast uptake of CO2 is observed during the first days as the use of finely ground hydrated samples resulted in a relatively fast and uniform carbonation.

    “The TGA data show that for all the samples, regardless of the activator used, a relatively fast uptake of CO2 is observed during the first days as the use of finely ground hydrated samples resulted in a relatively fast and uniform carbonation (Figure 1 (a)).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The thermodynamic calculations predict upon carbonation the destabilization of katoite and hemicarbonate to monocarbonate and eventually to strätlingite, and CO2 uptake by LDH.

    “The thermodynamic calculations predict upon carbonation the destabilization of katoite and hemicarbonate to monocarbonate and eventually to strätlingite, and CO2 uptake by LDH.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    C-(N-)A-S-H and hydrotalcite are identified as the reaction products in the XRD pattern of Na2SiO3-activated slag, while strätlingite formation is not clearly observed, in contrast to the thermodynamic predictions.

    “Specifically, C-(N-)A-S-H and hydrotalcite are identified as the reaction products in the XRD pattern (Figure 9), while strätlingite formation is not clearly observed in the Na2SiO3-activated slag, in contrast to the thermodynamic predictions.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning

    The MCL of C-(N-)A-S-H in the hydrated Na2SiO3-activated sample calculated using the spectral deconvolution and the modeling is similar, showing values of 13 and 11; thus, it is slightly higher than that present in the NaOH-activated slag, which is attributed to the SiO2 added to the system by the activator, increasing the chain length.

    “The MCL of C-(N-)A-S-H in the hydrated sample calculated using the spectral deconvolution and the modeling is similar, showing values of 13 and 11 (Figure 7); thus, it is slightly higher than that present in the NaOH-activated slag, which is attributed to the SiO2 added to the system by the activator, increasing the chain length 4,55 .”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [4] source
    • cites [55] source

  • May combine two claims.

    Findingown data

    In the XRD pattern of the Na2SO4-activated slag, the amount of ettringite notably decreases after 1 d of carbonation, and vaterite and calcite reflections appear as carbonation products.

    “The amount of ettringite notably decreases after 1 d of carbonation in the XRD pattern, which also shows the reflections of vaterite and calcite as carbonation products.”
    Quote in the paperNot a substantial claim

  • The quote only partly states this claim.

    Findingreasoning

    M-A-S-H is predicted stable after ~0.6 d of carbonation.

    “A-S-H is predicted stable after ~0.6 d of carbonation.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The XRD patterns of the Na2SiO3-activated slag samples after carbonation mainly show reflections due to calcite with minor reflections due to vaterite, implying that the thermodynamically more stable calcium carbonates are predominantly formed in the Na2SiO3-activated slag by carbonation, thus showing less kinetic effects than the NaOH-activated slag system.

    “The XRD patterns of the Na2SiO3-activated slag samples after carbonation mainly show reflections due to calcite with minor reflections due to vaterite, implying that the thermodynamically more stable calcium carbonates are predominantly formed in the Na2SiO3activated slag by carbonation, thus showing less kinetic effects than the NaOH-activated slag system.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The DTG curves of the carbonated Na2SO4-activated slag samples exhibit two decarbonation humps centered at 510 °C and 635-660 °C, with the latter becoming stronger over carbonation time.

    “The DTG curves of the carbonated samples exhibit two decarbonation humps centered at 510 o C and 635-660 o C with the latter one becoming stronger over carbonation time, and the curves show that carbonation progressively occurs in the samples over time.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning

    The thermodynamic calculation predicts ettringite to be stable even after 90 d of carbonation, which did not occur in the experiment.

    “The most notable difference between the thermodynamic calculation and the obtained experimental results is that gypsum (CaSO4•2H2O) is predicted to form instead of bassanite (CaSO4•0.5H2O),and ettringite is predicted to be stable even after 90 d of carbonation, which did not occur in the experiment.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In agreement with the calculations, carbonation reduces the intensity of the monocarbonate/LDH and the C-(N-)A-S-H phase as illustrated in XRD, which implies that these phases are carbonated.

    “In agreement with the calculations presented above it was found experimentally that carbonation reduces the intensity of the monocarbonate/LDH and the C-(N-)A-S-H phase as illustrated in XRD, which implies that these phases are carbonated.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Despite the mineralogical difference in the carbonation products formed in the Na2SiO3- and NaOH-activated slag samples, both samples exhibit a similar decarbonation behavior in the DTG curves, showing onset and offset temperatures at 310-350 °C and 660-680 °C, respectively.

    “Despite the mineralogical difference in the carbonation products formed in the Na2SiO3-and NaOH-activated slag samples, both samples exhibit a similar decarbonation behavior in the DTG curves, showing onset and offset temperatures at 310-350 o C and 660-680 o C, respectively (Figure 4 and Figure 10).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingreasoning

    The Na2SO4- and Na2CO3-activated samples exhibit a total CO2 uptake of approximately 10 g/100 g unreacted slag, while the Na2SiO3- and NaOH-activated slag show CO2 uptakes of 15 g/100 g and 19 g/100 g, respectively.

    “The Na2SO4-and Na2CO3 activated samples exhibit a total CO2 uptake of approximately 10 g/ 100 g unreacted slag, while the Na2SiO3-and the NaOH-activated slag show CO2 uptakes of 15 g/100 g and 19 g/100 g, respectively, which is related to both the different degrees of slag reaction and different chemistries depending on the activator used.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The NaOH-activated slag has the highest CO2 binding capacity of 23.3 g per 100 g of hydrated slag (1 to 91 d), followed by Na2SiO3 (20.0 g/100g), Na2SO4 (15.8 g/100g) and Na2CO3 (13.8 g/100g).

    “The CO2 uptake of the samples per mass of hydrated slag in Figure 23 suggests that the NaOH-activated slag has the highest CO2 binding capacity of 23.3 g per 100 g of hydrated slag (1 to 91 d), followed by that activated with Na2SiO3 (20.0 g/100g), Na2SO4 (15.8 g/100g) and Na2CO3 (13.8 g/100g).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingnone given

    Although C-(N-)A-S-H was decalcified and its amount notably decreased after carbonation, C-(N-)A-S-H was not completely destabilized.

    “(4) Although C-(N-)A-S-H was decalcified and its amount notably decreased after carbonation, C-(N-)A-S-H was not completely destabilized.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The CO2 uptakes per mass of hydrated slag for samples activated with NaOH, Na2CO3, Na2SiO3 and Na2SO4 were 23.3, 21.0, 20.0, and 15.8 g per 100 g, respectively, suggesting that the CO2 binding capacity can be activator-dependent.

    “(6) The CO2 uptakes per mass of hydrated slag for the samples activated with NaOH, Na2CO3, Na2SiO3 and Na2SO4 were 23.3, 21.0, 20.0, and 15.8 g per 100 g, respectively, suggesting that the CO2 binding capacity can be activator-dependent.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The pH of the simulated pore solution in NaOH- and Na2CO3-activated samples is calculated to remain above 12 and 13, respectively, while the pH within the other two samples is predicted to drop to 10-11 during carbonation.

    “The pH of the simulated pore solution in the NaOH and Na2CO3 activated samples is calculated to remain above 12 and 13, respectively, while the pH within the other two samples is predicted to drop to 10-11 during carbonation (Figure 24).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In the present study, high pH values are calculated by the modeling for these activators, which also showed a high CO2 uptake per g of hydrated slag.

    “In the present study, high pH values are calculated by the modeling for these activators, which also showed a high CO2 uptake per g of hydrated slag.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    When CO2 added by the activator is considered, the Na2CO3-activated slag takes up 21.0 g/100g, slightly higher than Na2SiO3, although its degree of slag reaction is 55% lower than the 70% reaction degree of NaOH- and Na2SiO3-activated slags.

    “If the uptake of CO2 added by the activator is also considered, the Na2CO3-activated slag takes up 21.0 g/100g, which is slightly higher than that of Na2SiO3, although the degree of slag reaction of the Na2CO3-activated slag is 55% lower than the 70% reaction degree of the NaOH-and Na2SiO3-activated slags.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Both thermodynamic modeling and 29Si MAS NMR deconvolution indicate an increase of MCL due to decalcification of C-(N-)A-S-H during carbonation, but the obtained values vary significantly.

    “Both techniques indicate an increase of MCL due to the decalcification of C-(N-)A-S-H during carbonation, but a significant variation in the obtained values occurs.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    A high alkali dosage may improve the carbonation resistance of alkali-activated slag by enhancing the slag reaction and reducing the porosity.

    “A high alkali dosage may improve the carbonation resistance of alkali-activated slag by enhancing the slag reaction and reducing the porosity 29 .”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [29] source

  • Probably not a substantial claim: may not pass S4 (based). May combine two claims.

    Study design and conductnone given

    Grinding the samples to pass a 100 μm sieve allowed carbonation to occur uniformly in the samples and reduce sampling errors.

    “After 50 d of curing, the samples were manually ground with a mortar and pestle to pass a 100 µm sieve, allowing carbonation to occur uniformly in the samples and reduce sampling errors.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Interpretationreasoning

    This could indicate that either the Al-uptake in C-(N-)A-S-H is underestimated in the model, and/or that the strätlingite present is poorly crystalline and thus not well visible by XRD.

    “This could indicate that either the Al-uptake in C-(N-)A-S-H is underestimated in the model, and/or that the strätlingite present is poorly crystalline and thus not well visible by XRD.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    In Na2SO4-activated slag, the stability of ettringite and zeolites is preferred over MgAl-LDH upon carbonation, resulting in stabilizing M-A-S-H.

    “It can be attributed to the additional SiO2 provided by the activator in the former case, and stability of ettringite and zeolites is preferred over MgAl-LDH upon carbonation, resulting in stabilizing M-A-S-H in the latter case.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    The phenomenon of underestimated carbonation performance under accelerated conditions limits the use of experimental data obtained under accelerated conditions for understanding the carbonation of alkali-activated slag, and does not allow quantitative comparison of its performance with data for Portland cement-based systems.

    “This phenomenon limits not only the use of experimental data obtained under accelerated conditions for understanding the carbonation of alkali-activated slag, but also does not allow quantitative comparison of its performance with the data for Portland cement-based systems widely available in literature.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    The lack of a definite decreasing trend in residual slag after the first day might be related to measurement error associated with the NMR technique and spectral deconvolution.

    “The carbonated samples generally have lower amounts of the residual slag, but they show no definite decreasing trend as a function of carbonation time after the first day, which might be related with the measurement error associated with the NMR technique and the spectral deconvolution process.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    A thermodynamic modeling study by Myers et al. suggests that the source of this error can be due to another phase (zeolites or geopolymer gels) missing in the database, which preferentially forms over strätlingite.

    “A thermodynamic modeling study by Myers et al. 13 suggests that the source of this error can be due to another phase (zeolites or geopolymer gels) missing in the database, which preferentially forms over strätlingite.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [13] source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationnone given

    It is possible that the high alkalinity of the NaOH activator as compared to the other activators may lead to higher reaction degree of slag.

    “It is possible that the high alkalinity of the NaOH activator as compared to the other activators may lead to higher reaction degree of slag.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    SiO2 added by the activator may stabilize M-A-S-H and destabilize MgAl-LDH, which buffers the pH of the pore solution.

    “For instance, SiO2 added by the activator may stabilize M-A-S-H and destabilize MgAl-LDH, which buffers the pH of the pore solution.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Study design and conductreasoning

    The activator dosages were identically applied on a mass basis (10 g of each), so the Na2O/slag mass ratios were different across the samples.

    “On the other hand, the activator dosages were identically applied on a mass basis (10g of each); thus, the Na2O/slag mass ratios were different across the samples.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductreasoning

    The NaOH-activated system had the highest Na2O dosage, which may have affected its pH evolution, CO2 buffering capacity and overall carbonation behavior.

    “The NaOH-activated system had the highest Na2O dosage, which may have affected its pH evolution, CO2 buffering capacity and overall carbonation behavior.”
    Quote in the paperNot a substantial claim
42 of 42

  • The authors state this as an assumption.

    The thermodynamic calculations assume a congruent dissolution of the slag.

    “The thermodynamic calculations were carried out by assuming a congruent dissolution of the slag.”
1 of 1

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Sodium-silicate dosage conflicts with the mixture table

    Major

    The methods say the hydrated activator dose was adjusted to supply 10 g of Na2SiO3. Table 2 instead lists 10.0 g of Na2SiO3•5.3H2O, which necessarily contains less than 10 g of Na2SiO3. This also calls the stated Na2O dosage for that mixture into question.

  • Stated water-to-binder ratio differs from Table 2

    Minor

    The methods state a water-to-binder ratio of 0.495 for all mixtures, whereas Table 2 labels the ratios as 0.450 or 0.406. The table's values therefore do not match the stated ratio.

2 of 2

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Authors
Park, S., Lothenbach, B., Jang, J. G., Kim, H.-K., & Lee, N.
Affiliations
  • Korea Advanced Institute of Science and Technology (KR)
  • Norwegian University of Science and Technology (NO)
  • Incheon National University (KR)
  • Chosun University (KR)
  • Korea Institute of Civil Engineering and Building Technology (KR)
Corresponding author
  • Park, Solmoi
  • Jang, Jeong Gook
ORCID
Venue
ACS Sustainable Chemistry & Engineering
Publisher
American Chemical Society (ACS)
Published
2023-03-02
Volume
11
Issue
10
Pages
4049-4063
ISSN
2168-0485 (ISSN-L)
DOI
10.1021/acssuschemeng.2c05789
OpenAlex
W4322767038
Cited by
43
References
66
Citations by year
2026: 19 · 2025: 7 · 2024: 15 · 2023: 1 · 2022: 1
FWCI
4.92
Type
journal article
Language
en
Open access
Licence
Locations
  • ACS Sustainable Chemistry & Engineering (publishedVersion)
  • DORA Empa (Swiss Federal Laboratories for Materials Science and Technology (Empa)) (submittedVersion, other-oa)
  • NORA - Norwegian Open Research Archives (submittedVersion, cc-by)
Funders
  • Schweizerischer Nationalfonds zur F?rderung der Wissenschaftlichen Forschung (EG-KR-07-092018)
  • National Research Foundation of Korea (2021R1A2C2004354, 2021R1A4A3033128, 2021R1C1C1013864, 2022R1C1C1007498, EG-KR-07-092018)
Topics
  • Physical Sciences › Engineering › Civil and Structural Engineering › Concrete and Cement Materials Research
  • Physical Sciences › Environmental Science › Environmental Engineering › CO2 Sequestration and Geologic Interactions
  • Physical Sciences › Engineering › Mechanical Engineering › Carbon Dioxide Capture Technologies
Keywords
alkali-activated slag, carbonation, thermodynamic modeling, sodium hydroxide activator, sodium silicate activator, sodium carbonate activator, sodium sulfate activator, sodium aluminosilicate hydrate, strätlingite, Mg-Al layered double hydroxide, calcium carbonate, ettringite, decalcification, carbon dioxide

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-11.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-11.

Cited sources are checked by gpt-6-sol.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

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