Influence of Mineral Additions in the Inhibition of Delayed Ettringite Formation in Cement Based Materials – A Microstructural Characterization

Abstract:

The degradation of concrete structures caused by delayed ettringite formation (DEF) is a problem that affects many concrete structures worldwide [1]. This pathology is due to the formation of expansive ettringite inside the material and is very difficult to deal with, because presently there is no efficient method to repair concrete structures affected by DEF. Hence, there is an urgent need to find preventive methods that may enable the inhibition of DEF in new constructions. This paper presents the findings of a long-term study [2,3] on the expansion rate and microstructure of heat-cured concretes with different amounts of mineral additions, like fly ash, metakaolin, ground granulated blast-furnace slag, silica fume and limestone filler. For this purpose different concrete compositions were produced using the same binder, water/binder (w/b) ratios and aggregate type. The concretes were prepared and subjected to a heat-curing cycle and subsequently to two drying-humidification cycles. After these cycles the concrete specimens were immersed in water for long-term storage at 20 ± 2°C. Length changes of specimens were measured at regular intervals. The microstructures of old heat curing specimens were investigated by optical microscopy and SEM-EDS analysis. The results of the blended-concrete compositions were compared with control compositions, and the conclusions were extracted.

• Periodical: Materials Science Forum (Volumes 636-637)
• Pages: 1272-1279
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.636-637.1272
• Online since: January 2010
• Authors: António Santos Silva, D. Soares, L. Matos, Manuela M. Salta, L. Divet, Alexandre Pavoine, António Estevao Candeias, José Mirão
• Keywords: Blast Furnace Slag (BFS), Delayed Ettringite Formation (DEF), Fly Ash (FA), Limestone Filler, Metakaolin (MK), Scanning Electron Microscope (SEM), Silica Fume (SF)

References

[1] Divet, L., Pavoine, A., Clement, J.L., Silva, A.S., As Reacções Expansivas Internas no Betão Devidas à Formação de Etringite Retardada. Métodos de Diagnóstico e de Prognóstico, Encontro Nacional BETÃO ESTRUTURAL 2004, FEUP, Porto, Vol. 1, (2004).

[2] Silva, A.S., Ribeiro, A.B., Jalali, S., Divet, L., The use of fly ash and metakaolin for the prevention of alkali-silica reaction and delayed ettringite formation in concrete, International RILEM Workshop on Performance Based Evaluation and Indicators for Concrete Durability, Madrid, Spain (2006).

DOI: 10.1617/2912143802.007

[3] Divet, L. Fasseu, P., Silva, A.S., Optimization of the choice of cement in order to reduce the expansion of concrete as a result of delayed ettringite formation (DEF), Seventh CANMET/ACI International Conference on Durability of Concrete, Montreal, Canada (2006).

DOI: 10.14359/15940

[4] Braga Reis, M.O., Silva, H.S., Silva, A.S., AAR in Portuguese structures. Some case histories, Proceedings of the 10th ICAAR in Concrete, Melbourne, Australia (1996) 93-100.

[5] Silva, A.S., Degradação do betão por reacções álcalis-sílica. Utilização de cinzas volantes e metacaulino para sua prevenção, PhD Thesis, Univ. do Minho-LNEC, Guimarães (2005).

[6] Manuel d'identification des réactions de dégradation interne du béton dans les ouvrages d'art, Laboratoire Central des Ponts et Chaussées, Paris (1999) p.42.

[7] Taylor, H. F. W., Cement Chemistry, Academic Press Limited, (1990).

[8] Divet, L., Les réactions sulfatiques internes: les differentes sources de sulfates, les mécanismes et les facteurs determinants, in Seminário Luso-Francês - Degradação de estruturas por reacções expansivas de origem interna, LNEC/LCPC, Lisboa (2001).

[9] Pavoine, A., Divet, L., Réactivité d'une formule de béton vis-à-vis de la réaction sulfatique interne. Essais de performance. Techniques et méthodes des LPC., Projet de méthode d'essai des lpc, vol. 59 (2003), p.17.

DOI: 10.1617/13868

[10] Taylor, H.F.W., Famy, C. Scrivener, K.L., Delayed ettringite formation, Cem. Concr. Res. 31 (2001) 683-693.

DOI: 10.1016/s0008-8846(01)00466-5

[11] Ye, G., Liu, X. Schutter, G., Poppe, A. M., Taerwe, L., Influence of limestone powder used as filler in SCC on hydration and microstructure of cement pastes, Cem. Concr. Res. 29 (2007) 94-102.

DOI: 10.1016/j.cemconcomp.2006.09.003

[12] Rahhal, V., Talero, R., Early hydration of Portland cement with crystalline mineral addition, Cem. Concr. Res. 35 (2005) 1285-1291.

DOI: 10.1016/j.cemconres.2004.12.001