Solid-state NMR characterisation of the thermal transformation of a Hungarian white illite

Carroll, Donna L.; Kemp, Thomas F.; Bastow, T. J.; Smith, Mark E.

doi:10.1016/j.ssnmr.2005.04.001

Cited by 69 publications

(28 citation statements)

References 45 publications

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“…The low-frequency part, centered around − 93 ppm, is ascribed to Q 3 (0Al)-type SiO 4 tetrahedra in the smectite sheets, having three Si-O-Si bonds in the silicate sheet and one Si-O-M 2 bond to two M sites in the octahedral sheet through a tri-coordinated oxygen (M = Al 3+ , Fe 3+ , Mg 2+ ) [30,31]. The high-frequency part around −88 ppm corresponds to a Q 3 (1Al)-type SiO 4 environment from the illite sheets where the silicon atoms undergo isomorphic substitution by aluminum atoms, and the excess negative charge thus produced is balanced by the potassium ions in the interlayer [32,33]. Upon heating at 200°C, the overall center of gravity (Fig.…”

Section: Resultsmentioning

confidence: 99%

Pozzolanic reactivity of a calcined interstratified illite/smectite (70/30) clay

Garg

Skibsted

2016

Cement and Concrete Research

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Section: Resultsmentioning

confidence: 99%

Pozzolanic reactivity of a calcined interstratified illite/smectite (70/30) clay

Garg

Skibsted

2016

Cement and Concrete Research

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“…Figure 8 shows the 29 Si MAS NMR spectra of the MK and cement composites. The spectra of MK show a broad 29 Si resonance peak at around -95 ppm assigned to Q 3 ''sheet- Performance of metakaolin-blended cements 859 [64][65][66]. The conversion rate of 1 ppm to 1 mg L -1 takes 1 ppm = 0.99859 mg L -1 (1 ppm % 1 mg L -1 ).…”

Section: Resultsmentioning

confidence: 99%

Performance of composites with metakaolin-blended cements

Krajči

Mojumdar

Janotka

et al. 2014

J Therm Anal Calorim

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Nowadays the blended cements acquire the merit of high significance due to the thermal, energetic and ecological demands for ordinary Portland cement (PC) production. Metakaolin as a partial substitute of PC represents important pozzolana contributing to production of effective cement composites with high quality. Pozzolanic reaction of metakaolinite with PC in the presence of water is main reason of this statement. Comparison of three types of metakaolin sand (fineness below 60 lm) with different metakaolinite content (31-40 mass%) is presented in this study. The substitution of PC with metakaolin sand of the maximal metakaolinite content (40 mass%) leads to the highest compressive strengths of relevant composites. This is valid for composites with the highest substitution of PC by metakaolin sand in specimens (20 and 40 mass%). The best effectiveness of pozzolanic reaction is given especially by the highest consumption of portlandite which represents composite with the maximal metakaolinite content in metakaolin sand (40 mass%) and the higher substitution level of PC by metakaolin sand in specimens. This fact is connected with the improvement of pore structure parameters resulting in the pore structure refinement as well as permeability decreases. Both 29 Si MAS NMR and 27 Al MAS NMR spectra of metakaolin sands and respective composites confirm the most intense pozzolanic reaction in the case of metakaolin sand with the highest metakaolinite content (40 mass%). The results are properly supplemented by scanning electron microscopy (SEM) identifying the formed typical phases. The study has shown that metakaolin sand with reduced metakaolinite contents is also applicable as a pozzolanic addition to PC in the on-coming building practice.

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“…At first, up to 300°C, it loses physically bound water located in the water layers on the surfaces of illite crystallites. For illite, several DTG extremes are observed in this temperature region resulting from various types of bonds of water molecules to surfaces of illite crystallites or to T-O-T layers [4][5][6][7]. Also mass spectrometric results show two distinct peaks of escaping H 2 O gas.…”

Section: Introductionmentioning

confidence: 93%

“…The interlayer space is occupied with K ? ions and water molecules [4][5][6][7][8]. During heating up to 1200°C, illite undergoes several changes.…”

Section: Introductionmentioning

confidence: 99%

DC conductivity of illitic clay after various firing

Kubliha

Trnovcová

Ondruška

et al. 2015

J Therm Anal Calorim

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The temperature dependencies of the direct current (DC) conductivity of illitic clay, which contained 86 % of illite of 1 M polytype, were measured in a temperature range of 20-450°C, on green samples and on the samples after thermal treatments at 400-1200°C. The release of the physically bound water from a green sample takes place in three stages-at 72, 186 and 298°C. After heating at 400°C, the movement of dominant H ? and OHions is characterized by the conduction activation energy (CAE) of 0.31 ± 0.02 eV, below 220°C. At higher temperatures, K ? ions are dominant charge carriers with a CAE of 1.12 ± 0.02 eV. Upon heating at 450°C, the DC conductivity slightly increases; a slightly higher CAE (1.22 eV) indicates that K ? ions are moving in a more disordered structure, probably due to starting dehydroxylation. Significant structural changes, which influence the DC conductivity, are finished at 550°C. After preheating from 550 up to 1000°C, the defect structure, type, concentration, and mobility of charge carriers are not significantly changed as the temperature dependence of the DC conductivity is independent of the temperature of firing. During preheating at 1100°C, vitrification and sintering are almost completed. The high mobility of K ? ions in the glassy phase results in a high DC conductivity with the CAE equal to 0.76 eV.

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Solid-state NMR characterisation of the thermal transformation of a Hungarian white illite

Cited by 69 publications

References 45 publications

Pozzolanic reactivity of a calcined interstratified illite/smectite (70/30) clay

Pozzolanic reactivity of a calcined interstratified illite/smectite (70/30) clay

Performance of composites with metakaolin-blended cements

DC conductivity of illitic clay after various firing

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