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Concrete-damaging thaumasite formation? –
Examination of a case of damage
Univ.-Prof. Dr.-Ing. D. Heinz, Dr.-Ing. L. Urbonas,
Technische Universität München, Munich, Germany
Damage to the shotcrete and other concrete components was found in a tunnel that was about 30 years old. The aim of the investigations was to clarify the causes of the con-crete damage. The damaged concretes were characterized by X-ray diffractometry, nuclear magnetic resonance (NMR) spectroscopy, environment scanning electron microscopy (ESEM) and conventional chemical analysis. The seepage water and the bedrock were also characterized chemically and mineralogically (rock). The results of the investigation show that damage to the shotcrete and in-situ-cast concrete occurred at low temperatures (about 10 °C) due to the dissolving and carbonating action of the seepage water and condensed water or to a combination of dissolving and thaumasite-forming, partially internal, sulfate attack in spite of the relatively low levels of sulfate and lime-dissolving carbonic acid in the seepage water. The damage mechanisms are discussed.
Summary CEMENT INTERNATIONAL 01/2006 pp 90-101
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