Decay of Rhenish tuffs in Dutch monuments. Part 2: Laboratory experiments as a basis for the choice of restoration stone

• Published in: Heron Vol. 48; no. 3; pp. 167 - 177
• Main Authors: van Hees, R P J, Brendle, S, Nijland, T G, de Haas, GJLM, Tolboom, H J
• Format: Journal Article
• Language: English
• Published: 01.01.2003
• ISSN: 0046-7316

Rhenish tuffs (Eifel, Germany), have been used as building material in the Netherlands since Roman times. They were the most important natural building stone in the Netherlands in early medieval times. In addition, tuff was used as raw material for production of trass, that served as a pozzolanic addition for mortars. Rhenish tuffs, notably Romer, Weiberner and Ettringer, show remarkable differences in decay. Ettringer tuff applied during late 19th - early 20th century restorations often shows severe deterioration, whereas, for example, most 14th century Romer in rampant arches on top of St. John's cathedral, 's Hertogenbosch, resisted weathering reasonably well, as do sculptures out of the more fine-grained Weiberner tuff on top of these. In order to obtain a better understanding of the processes underlying the decay of these tuffs and the compositional factors controlling them, a research project was started that includes both on site investigations of major monumental buildings in the Netherlands (partly) built with tuff and laboratory research. Fresh quarry samples of Romer, Ettringer and Weiberner tuff were used for selected physical characterization and testing, including a.o. hydric dilation, drying behaviour and frost resistance. One type of Romer showed a remarkably high resistance against frost. The results of the laboratory experiments on quarry samples are reported. The experiments provide a sound basis for the choice of restoration stone.