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ECN publication
Evaluatie van de gevolgen van aanpassing van de pH van de uitloogvloeistof in de uitloognormen NEN 7343, 7345 en 7349
Published by: Publication date:
ECN 1-8-2000
ECN report number: Document type:
ECN-C--00-081 ECN publication
Number of pages: Full text:
27 Download PDF  

During discussions in the Dutch standardisation committee 390011'Leaching behaviour of building materials and waste materials' on the quality of leaching standards a modification of pH of the leachant for the column test (NEN 7343) and the tank leach test (NEN 7345) was addressed. The sometimes poor repeatability of the tests has been related to large pH jumps in the first fractions of both column and tank leach test. This can be caused by the acidification of the leaching solution to pH=4 in combination with a relatively short contact time relative to the time of contact in field scenarios. The undesired side effects can be reduced or eliminated by applying a neutral leaching solution. An additional reason for this is the use of a neutral solution in European standards. In this report a wide range of materials is evaluated to identify if such a change would lead to a different judgement from a regulatory point of view. An extended experimental program would be too costly, therefore a choice has been made to judge these possible changes on the basis of the acid neutralization capacity in combination with pH dependence test data to quantify the effect of the change from acidified to a neutral leaching solution. From the evaluation it shows that pH differences in the extracts are generally small. As might be expected, the materials with a low buffer capacity are most sensitive. Such materials are: vitrified incinerator fly ash, some industrial slags and sintered products (artificial gravel and bricks). Most building materials and waste materials are not affected due to their high buffer capacity. Elements, which leach independent of pH such as Cl, Br and in many cases sulfate, are unaffected. No significant changes in judgement relative to the current regulation are expected. This also implies that existing data sets remain valid in the new situation. The standardization committee is advised to proceed with the change to a neutral leaching medium. For materials with a low buffer capacity and a significantly increased leaching upon acidification measures should be taken to avoid application in mildly acidic environments (peat, acidic soils). 18 refs.

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