Synthesis and characterisation of crystalline analogues of alkali-aggregate reaction products

Way, Steve; Shayan, A

doi:10.1016/0008-8846(93)90112-m

Cited by 5 publications

(3 citation statements)

References 5 publications

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“…The reaction mechanisms for alkali-aggregate reaction in concrete have been described both in generic terms (Bérubé and Fournier, 1986;Gillot, 1995;Way and Shayan, 1993;Brouxel, 1993) as well as for specific solids (e.g. Goguel, 1995).…”

Section: Analogue Evidencementioning

confidence: 99%

A review of analogues of alkaline alteration with regard to long-term barrier performance

Savage¹

2011

Mineral. mag.

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Cement and concrete will be used as fracture grouts, shotcrete, tunnel and borehole seals, and as matrices for waste encapsulation inter alia in geological repositories for radioactive wastes. Alteration of the host rock and/or swelling clay in waste package buffers and tunnel backfills by hyperalkaline solutions from cement/concrete may be deleterious to system performance through changes in the physicochemical properties of these barrier materials.Analogue systems (and timescales) relevant to the understanding of the alkaline disturbed zone include: industrial analogues, such as alkaline flooding of hydrocarbon reservoirs (up to 30 y), cementaggregate reactions (up to 100 y) and the Tournemire tunnel (up to 125 y); and natural analogues, including the hyperalkaline springs at Maqarin, Jordan (more than 100,000 y), saline, alkaline lakes (more than 1,000,000 y) and certain fracture fillings in granites (more than 1,000,000 y).These systems show that alkaline alteration can be observed for thousands of years over distance scales of hundreds of metres under extreme conditions of hydraulic gradients in fractured rocks (Maqarin), but may be limited to a few centimetres over tens to a hundred years in mudstone (Tournemire). Important reaction mechanisms for retardation of alkaline fluids include: fluid mixing (alkaline oil floods, Maqarin), ion exchange (alkaline oil floods, Tournemire) and kinetic mineral dissolution-precipitation reactions (all systems studied). Qualitative and quantitative kinetic data for mineral reactions are available from cement aggregate reactions and the Searles Lake analogue, respectively. Short-term alteration observed in cement-aggregates is characterized by calcium silicate hydrate (C-S-H) minerals and incipient zeolite formation, whereas evidence from the Tournemire tunnel shows the growth of K-feldspar after relatively short time intervals (tens to a hundred years). There is a tendency for alkaline alteration to result in porosity decreases, but locally, porosity may be enhanced (e.g. near-injection well interactions in alkaline oil floods, or at fracture margins at Maqarin, Jordan). Data from industrial and natural analogues may thus supply some key data for bridging time and space scales between laboratory and in situ experiments on one hand and the requirements for safety assessment on the other.

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Section: Analogue Evidencementioning

confidence: 99%

A review of analogues of alkaline alteration with regard to long-term barrier performance

Savage¹

2011

Mineral. mag.

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“…Knowledge of these scales is essential for understanding and predicting ASR expansion behavior and developing effective mitigation measures. Previous observations suggest that ASR gel has a poorly ordered layered structure dominated by Q 3 silicate tetrahedra 4–11 . Wieker et al 5–7 have proposed that ASR gel has a structure similar to that of the layer‐structure hydrous Na silicate, kanemite (NaHSi 2 O 5 ·3H 2 O) 12–15 .…”

Section: Introductionmentioning

confidence: 99%

“…Previous observations suggest that ASR gel has a poorly ordered layered structure dominated by Q 3 silicate tetrahedra. [4][5][6][7][8][9][10][11] Wieker et al [5][6][7] have proposed that ASR gel has a structure similar to that of the layer-structure hydrous Na silicate, kanemite (NaHSi 2 O 5 Á 3H 2 O). 12- 15 Brough et al 4 have demonstrated that C-S-H present with ASR gel is more polymerized than the C-S-H formed during hydration of ordinary Portland cement, and more recent studies support the coexistence of an alkali-rich silicate gel with little calcium and a more calcium-rich, C-S-H-like phase that contains some alkali.…”

Section: Introductionmentioning

confidence: 99%

Structural Investigations of Alkali Silicate Gels

Hou

Kirkpatrick

Struble

et al. 2005

Journal of the American Ceramic Society

113

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Investigation of a series of synthetic alkali silicate gels and gels produced by the alkali silica reaction (ASR) in field concrete using 29Si NMR spectroscopy, X‐ray diffraction, and bulk chemical analysis shows that local structures of the synthetic and field gels are quite similar. The most abundant Si sites for the field and synthetic gels with similar compositions have Q3 polymerization, and the number of non‐bridging oxygens per Si is similar for these samples. These samples also yield a basal X‐ray diffraction peak near 8–12 Å, suggesting that the structure is dominated by sheet‐like units, consistent with the dominant Q3 polymerization. Calculations based on the relative site abundances of the sites observed by 29Si NMR and the bulk chemical compositions indicate that there is insufficient alkali to charge‐balance all the non‐bridging oxygens and that there is a significant concentration of Si–OH linkages. The results provide strong support for the basic structural concepts of the so‐called kanemite model for ASR gel proposed by Wieker and coworkers, although the overall gel structure is likely to be more complex.

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IR Spectroscopy

Ghosh¹

2001

Handbook of Analytical Techniques in Concrete Science and Technology

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Synthesis and characterisation of crystalline analogues of alkali-aggregate reaction products

Cited by 5 publications

References 5 publications

A review of analogues of alkaline alteration with regard to long-term barrier performance

A review of analogues of alkaline alteration with regard to long-term barrier performance

Structural Investigations of Alkali Silicate Gels

IR Spectroscopy

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