Forschungs- & Entwicklungsinformationsdienst der Gemeinschaft - CORDIS

Laboratory test method for risk of bowing

The developed test method exposes standard sized test specimens to systematic temperature and moisture variations over a time period up to 50 days. The bowing is measured during the testing period and provides a evaluation basis for the assessment of the stone materials risk of bowing and also information for the assessment of the stone panels durability in environments where the stone is used as cladding and is exposed to sun and rain (concerns almost all external claddings).

The test method has been correlated to observations from the cladding of the structures and to petrographic examination of the microstructure and has shown a good correlation. The method should be able to provide a good and realistic assessment of a stone's tendency to deteriorate and bow on exterior claddings. In combination with non destructive (e.g. sound velocity) and/or destructive tests (e.g. flexural strength) additional durability data can be achieved.

This test method is the first method for natural stones which provides data, that can be used for this assessment and will therefore be essential to guidelines, specifications and technical standards at European level. It has particular relevance to Directive Council Directive EEC 89/106 of 21 December 1988 on the approximation of laws, regulations and administrative provisions of the Member States relating to construction products.

Decision makers, architects and building owners who select stones for claddings will need the results of this test method as a basis for their selection and the documentation of the durability. Such stones are currently selected, typically based on their appearance.

Natural stone producers will have a major interest in having their stones tested or implement the test method them selves for Initial type testing or FPC in addition to other tests already specified and required for natural stones (water absorption, flexural strength, frost durability etc.)

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Reported by

Rambøll, Hannemann & Højlund A/S
Bredevej 2
2830 Virum
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