ECN publication
Considerations on the discrimination of “solubility” versus “diffusion” control in renewal time schedules of the tank test (TS2)
Published by: Publication date:
ECN Environment & Energy Engineering 14-11-2013
ECN report number: Document type:
ECN-E--13-043 ECN publication
Number of pages: Full text:
30 Download PDF  

European regulations on CE marking of construction products are presently harmonized with respect to requirements on the potential release of “dangerous substances” to the environment. In order to judge the potential release of dangerous substances, laboratory tests are developed and standardized. In the EU standardization committee TC 351, a harmonized test method is developed and standardized for the release of substances from “monolithic” construction products (e.g., concrete) to water (e.g., rainwater). This test method is called a “tank test” as it is based on a vessel (“ tank”) with water, in which a product is submersed for a certain time period to allow diffusion from the substances to the water phase. After this time period, the concentration of released substances is measured in the water (“leachant”). This procedure is repeated a number of times (“leachant renewals”), after which the total release of a substance is determined. Similar procedures are already used on national level in EU member states and implemented in environmental legislation (e.g., the Dutch tank test NEN7375). Presently the European test is in the phase of “robustness testing” (to investigate potential variability in outcome, as a function of certain test parameters). A focal point is the discrimination between “ solubility” and “diffusion” processes by which substances are released. This report is used for technical discussions (2012) on the discrimination between these processes in tank tests as a function of amount and duration of renewal times. The report reviews current approaches on discrimination between the different release processes, both theoretical and by using actual measurement data. It is written for a technical / scientific audience involved in standardization of release tests. The main conclusion is that too much detail in interpretation and assessment of possible solubility/diffusion mechanisms is not justified by the large uncertainties and conditionality in identifying such mechanisms, and their expected limited meaning for scenarios in practice. Based on these considerations, improved assessment methods are proposed, and the time schedule of the current NEN 7375 test method is recommended.

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