Sulphate attack

Concrete can be severly damaged by sulfate attack due to the formation of ettringite, thaumasite and gipsum. In Switzerland, this is mainly a problem in tunnels, where an interaction between concrete and sulfate bearing groundwater can take place and sewage systems. The damage occurring depends on the chemical composition of the cement, its physical properties and the chemical composition of the attacking solution. These factors determine the kind and amount of secondary products formed and thereby the extent of damage to the structure.
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We study the influence of different sulfate solutions on systems with various cements experimentally. The results are used for thermodynamic modelling permitting a better understanding of the reactions present. One of this results, it was shown that ettringite forms at an initial state of sulfate attack. Thaumasite is only formed at a latter stage when molar SO3/Al2O3 ratio exceeded 3. A prerequesite for thaumasite formation is the presence of carbonates that can be provided by fillers or the aggregates.

As a way of validation we compare the results of the laboratory experiments with the phenomena on real structures. Furthermore, we look for possibilities to test the sulfate resistance of concrete.

Important publications and documents to sulfate

Leemann, A./Loser, R. Accelerated sulfate resistance test for concrete – chemical and mircrostructural aspects. The 2nd International Conference on Microstructural-related Durability of Cementitious Composites Amsterdam, The Netherlands, April 11-13, 2012

Leemann, A./Loser, R. Analysis of concrete in a vertical ventilation shaft exposed to sulfate-containing groundwater for 45 years. Cement & concrete composites 2011, 74–83
Leemann, L./Lothenbach, B./Siegrist, H./Hoffmann, C. Influence of water hardness on concrete surface deterioration caused by nitrifying biofilms in wastewater treatment plants. International Biodeterioration & Biodegradation 64 (2010) 489 - 498
Leemann, L./Lothenbach, B./Hoffmann, C. Biologically induced concrete deterioration in a wastewater treatment plant assessed by combining microstructural analysis with thermodynamic modeling. Cement and Concrete Research 40 (2010) 1157–1164
Kunther, W./Lothenbach, B./Scrivener, K. Influence of carbonate in sulfate environments. Concrete in aggressive aqueous environments - Performance, Testing, and Modeling, Toulouse, France, 3-5 June 2009, 498-499. /CP
Schmidt, T./Lothenbach, B./Scrivener, K. L./Romer, M./Rentsch, D./Figi, R. Conditions for Thaumasite formation. 12th International Congress on the Chemistry of Cement, Montréal, Canada, July 8-13, 2007, 12 pp. /CP
Romer, M./Holzer, L. What triggers concrete deterioration in aqueous underground environments? 11th Int. congress on the chemistry of cement (ICCC): cement' s contribution to the development in the 21st century, Durban, South Africa, May 11-16, 2003, p. 1432-1438. ISBN 0-9584085- 8-0, 1432-1438. ISBN 0-9584085- 8-0.
 Romer, M./Holzer, L./Pfiffner, M. Swiss tunnel structures: concrete damage by formation of thaumasite. Cement & concrete composites 2003, 25/ISI_SciCi

Research results: collaboration with Cemsuisse