Alkali-activated metakaolin-slag blends—performance and structure in dependence of their composition

Buchwald, Anja; Hilbig, H.; Kaps, Ch.

doi:10.1007/s10853-006-0525-6

Cited by 241 publications

(116 citation statements)

References 10 publications

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“…This phase detected before in PC/slag blends [67] and it was also reported in the slags activated with NaOH [44, 60,68,[69][70][71], waterglass [69], sodium silicate (4% Na 2 O, 8% Na 2 O) [72] and solid Na-metasilicate pentahydrate (Na 2 SiO 3 .5H 2 O) [73].…”

Section: Crystalline Phasessupporting

confidence: 61%

Hydration and properties of sodium sulfate activated slag

Rashad

Bai

Basheer

et al. 2013

Cement and Concrete Composites

269

103

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Section: Crystalline Phasessupporting

confidence: 61%

Hydration and properties of sodium sulfate activated slag

Rashad

Bai

Basheer

et al. 2013

Cement and Concrete Composites

269

103

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“…The temperature at which the weight loss is most rapid (i.e., the minimum in the differential thermograms plotted in Figure 2) is similar for the three samples at 62°C, in good agreement with results previously identified for alkali-activated GBFS/MK systems with high slag content, where the structure of the binders is dominated by the activation of the slag (Buchwald et al, 2007;Bernal et al, 2011a). The fact that more weight is lost by samples with GBFS/(GBFS + MK) = 0.8 might indicate that water is more loosely bound in the reaction products forming in this paste.…”

Section: Thermogravimetrysupporting

confidence: 90%

Microstructural Changes Induced by CO2 Exposure in Alkali-Activated Slag/Metakaolin Pastes

Bernal

2016

Front. Mater.

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The structural changes induced by accelerated carbonation in alkali-activated slag/ metakaolin (MK) cements were determined. The specimens were carbonated for 540 h in an environmental chamber with a CO2 concentration of 1.0 ± 0.2%, a temperature of 20 ± 2°C, and relative humidity of 65 ± 5%. Accelerated carbonation led to decalcification of the main binding phase of these cements, which is an aluminum substituted calcium silicate hydrate (C-(N-)A-S-H) type gel, and the consequent formation of calcium carbonate. The sodium-rich carbonates trona (Na2CO3·NaHCO3·2H2O) and gaylussite (Na2Ca(CO3)2·5H2O) were identified in cements containing up to 10 wt.% MK as carbonation products. The formation of these carbonates is mainly associated with the chemical reaction between the CO2 and the free alkalis present in the pore solution. The structure of the carbonated cements is dominated by an aluminosilicate hydrate (N-A-S-H) type gel, independent of the MK content. The N-A-S-H type gels identified are likely to be derived both from the activation reaction of the MK, forming a low-calcium gel product that does not seem to undergo structural changes upon CO2 exposure, and the decalcification of C-(N-)A-S-H type gel. The carbonated pastes present a highly porous microstructure, more notable as the content of MK content in the cement increases, which might have a negative impact on the durability of these materials in service.

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“…There are approaches which correlated these signals with aluminosilicate compounds (Q 4 (3Al) and Q 4 (2Al)), such as in alkaliactivated mixtures of blast furnace slag and metakaolin [38]. Another possible explanation could be that pure silicate gel is precipitated.…”

Section: Nuclear Magnetic Resonance Spectroscopymentioning

confidence: 99%

“…From the deconvolution results, the degree of reaction (DR) of GGBFS, the average chain length (mean chain length-MCL) and the Si/Al-ratio of the C-(A)-S-H phases are calculated [35,38,42,43]. The formulas are quoted elsewhere [38].…”

Section: Nuclear Magnetic Resonance Spectroscopymentioning

confidence: 99%

Effect of slag chemistry on the hydration of alkali-activated blast-furnace slag

2014

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This paper presents results of detailed investigations about the alkaline activation of ground granulated blast furnace slags whose chemical composition were modified. Sodium hydroxide and potassium silicates were used as alkaline activators. The influence of the CaO/SiO 2 ratio, the Al 2 O 3 and TiO 2 content of the slag composition on the hydration reaction was analyzed utilizing isothermal heat flow calorimetry, compressive strength development of binder samples, 29 Si MAS NMR spectroscopy and molybdate method. It could be shown that the TiO 2 content of the slag has only minor influence on the hydraulic reactivity and compressive strength of the alkaline activated binders.The variation of the Al 2 O 3 content of the slag leads to different results. A rise in Al 2 O 3 content enhanced the strength if activating with NaOH but resulted in a lower strength if activating with potassium silicate. The results of the 29 Si MAS NMR spectroscopy verify the decrease in the reaction degree with increase of Al 2 O 3 content. This is associated with the rise of the chain length of the C-(A)-S-H phases by incorporation of Al-O tetrahedrons resulting in a lower Si/Al-ratio. A decrease in the C/S-ratio yielded to a lower heat evolution, whereas the reaction was delayed if activated with potassium silicate with higher silicate content. The increase of the C/S-ratio caused in less condensed slag glass and therefore an enhancement of the reaction degree with a simultaneous decrease of silicate chain length, as seen by 29 Si NMR. These outcomes fit well with the results measured by the molybdate method.

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Alkali-activated metakaolin-slag blends—performance and structure in dependence of their composition

Cited by 241 publications

References 10 publications

Hydration and properties of sodium sulfate activated slag

Hydration and properties of sodium sulfate activated slag

Microstructural Changes Induced by CO2 Exposure in Alkali-Activated Slag/Metakaolin Pastes

Effect of slag chemistry on the hydration of alkali-activated blast-furnace slag

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