Field experiences in concrete deterioration by thaumasite formation: possibilities and problems in thaumasite analysis

摘要

In Germany, after testing two concretes deteriorated due to the formation of thaumasite, possibilities and problems in analysing thaumasite and ettringite-containing concrete samples will be discussed. The image of polished thin sections show, that thaumasite formation leads to microstructures similar to the microstructure of ettringite. It is recognisable in the microstructure that the formation of thaumasite happens as well via deterioration of CSH-phases as via the decomposition of ettringite. The identification of thaumasite using environmental scanning electron microscopy is possible without problems. Investigations using X-ray powder diffraction did show, that quantitative analysis of thaumasite and ettringite is possible by using the Rietveld method. The samples of deteriorated concrete (excluding coarse aggregate) contain 20-75 percent thaumasite.