Opóźnienie powstawania ettringitu - krótki przegląd

• Autorzy: Bensted J. , Munn J.

Warianty tytułu

EN

Delayed ettringite formation - a concise view

• Języki publikacji: PL

Abstrakty

PL

Opóźnione powstawanie ettringitu (OPE) powinno być odróżnione od wtórnego powstawania ettringitu. OPE obejmuje znane od dawna zjawisko cieplnego powstawania spękań. OPE nie występuje normalnie w przypadku dojrzewania betonu w pokojowej temperaturze. OPE można uniknąć jeżeli dojrzewanie betonu przeprowadza się w możliwie niskich temperaturach, nie przekraczających 60°C. OPE jest przeważnie formą wewnętrznej korozji siarczanowej, lecz czasem może być także spowodowane zewnętrzną agresją. OPE nazywa się często "słabą" korozją siarczanową. Jednak powstawanie pęknięć może umożliwić dostęp wilgoci i pociągnąć za sobą inne procesy korozyjne. Dobre zaprojektowanie i wykonanie konstrukcji ma podstawowe znaczenie w uniknięciu OPE, szczególnie w przypadku niskiego stosunku w/c. Potrzeba więcej badań w celu lepszego poznania tego zjawiska.

EN

Delayed ettringite formation (DEF) needs to be properly distinguished from secondary ettringite formation (SEF). DEF embraces thermal cracking that has been around for a long time. DEF does not normally occur in concrete cured at normal temperatures. Avoidance of DEF can be facilitated by keeping the curing temperatures as low as possible, below around 60°C. DEF is mostly internal sulphate attack, but sometimes there can be external attack too. DEF is often called a 'weak' form of sulphate attack. However, upon cracking, other deleterious phenomena can access the concrete within the cracks, especially with moisture transport. Good design and execution of the construction is essential for militating against DEF by lowering water/cement ratios as far as is practical. More research and development are needed to understand this phenomenon better.

Słowa kluczowe

PL

cement portlandzki; mieszanka betonowa; hydratacja; etryngit; powstawanie etryngitu; opóźnienie; ekspansja

EN

Portland cement; concrete mix; hydration; ettringite; ettringite formation; delay; expansion

• Wydawca: Fundacja Cement, Wapno, Beton
• Czasopismo: Cement Wapno Beton
• Rocznik: 2009
• Tom: R. 14/76, nr 5
• Strony: 240--244
• Opis fizyczny: Bibliogr. 15 poz., il.

Twórcy

autor

Bensted J.

autor

Munn J.

• University College London, Materials Chemistry Centre and Department of Chemical Engineering, London, UK

Bibliografia

• 1. Deutsche Ausschuß für Stahlbeton: 'Richtlinie zur Wärmebehandlung von Beton'. Beuth-Verlag GmbH, Berlin und Köln, (1989).
• 2. Y. Fu and J. J. Beaudoin: On the distinction between delayed and secondary ettringite formation in concrete. Cement and Concrete Research, 26, 979-980 (1996).
• 3. J. Bensted and J. Munn: A discussion of the paper 'On the distinction between delayed and secondary ettringite formation in concrete' by Y. Fu and J.J. Beaudoin. Cement and Concrete Research, 27, 1773-1775 (1997).
• 4. J. Bensted: A discussion of the review paper 'Sulphate attack research - whither now?' by M. Santhanam, M. D. Cohen and J. Olek: Cement and Concrete Research, 32, 995-1000 (2002).
• 5. C. Famy, K, L. Scrivener and H.F.W. Taylor: Delayed ettringite formation. in 'Structure and Performance of Cements', 2nd Edition, (Eds. J. Bensted and P. Barnes) pp. 282-294, Spon Press, London and New York (2002).
• 6. J. Bensted, A. R. Brough and M.M. Page: Chemical degradation of concrete, in 'Durability of Concrete and Cement Composites', (Eds. C.L. Page and M.M. Page), pp. 86-135. Woodhead Publishing Limited, Cambridge, (2007).
• 7. C. D. Lawrence: Delayed ettringite formation: An issue?, in 'Materials Science of Concrete IV, (Eds. J.P. Skalny and S. Mindess), pp. 113-154. American Cerarnic Society, Westerville, Ohio (1995).
• 8. C. Famy, A. R. Brough, K. L. Scrivener and A. Atkinson: Effects of early or a late heat treatment on the microstructure and composition of inner C-S-H products of Portland cement pastes. Cement and Concrete Research, 32, 269-278 (2002).
• 9. J. Bensted and J. Munn: Formazione ritardata dell’ettringite nell’idratazione del cemento calcio alluminoso./Delayed ettringite formation in calcium aluminate cement hydration. L’Industria Italiana del Cemento, No. 715,806-812 (1996).
• 10. R. Buckby, P. White, C. Mills and K. Quillin: Severe cracking in in-situ concrete substructures due to delayed ettringite formation. Concrete, 42, No. 2, 32-34 (March 2008).
• 11. R. Buckby, P. White and C. Mills: Structural assessment of the effects of delayed ettringite formation. Concrete, 42, No. 4, 39-40, 42 (May 2008).
• 12. S. Kelham: The effect of cement composition and fineness on expansion associated with delayed ettringite formation. Cement and Concrete Composites 18, 171-179 (1996).
• 13. S. Kelham: Effects of cement composition and hydration temperature on volume stability of mortar. Proceedings of the 10th International Congress on the Chemistry of Cement, 4iv060, 8pp. Amarkai AB and Congrex Göteborg AB, Gothenburg (1997).
• 14. W. Klemm and F. M. Miller: Plausibility of delayed ettringite formation as a distress mechanism - considerations at ambient and elevated temperatures. Proceedings of the 10th International Congress on the Chemistry of Cement, 4iv059. 10pp. Amarkai AB and Congrex Göteborg AB, Gothenburg (1997).
• 15. M. R. Hawkins et al.: 'Alkali-silica reaction - Minimising the risk of damage to concrete'. Concrete Society Technical Report No. 30, 3rd Edition. Concrete Society (UK), Camberley, Surrey (1999).