ECN publication
Leaching behaviour of artificial aggregates : EU project BRST-CT98-5234
Published by: Publication date:
ECN 1-12-2001
ECN report number: Document type:
ECN-C--01-014 ECN publication
Number of pages: Full text:
190 Download PDF  

In the framework of EU project "Utilising innovative kiln technologyto recycle waste into synthetic aggregate" (BRST-CT98-5234), the leaching behaviour of artificial aggregates has been studied to assess its environmental compatibility in the various stages of its use. Since the conditions are very different for the different applications, the assessment calls for a variety of different leaching test conditions. The pH dependence test is used to cover important differences in pH environment to which the materials are exposed to as wel1 as for an assessment of the acid buffering capacity of the material. It is found that artificial aggregate has a low buffer capacity, which makes it sensitive to externally imposed pH conditions. Utilisation and storage exposed to acidic conditions needs to be avoided. The results of the pH dependence test and column leaching test are mutually consistent while the CEN TC 154 method systematically provides lower values. The artificial aggregates studied here wil1 not adversely affect the concrete in its service life. The main issue for aggregate use is the recycling and the "end of life" condition, when the material becomes construction debris. Not metals, but oxyanions, such as Cr VI and Mo are most relevant under the recycling, reuse and "end-of life" condition. This is based on the criteria set by the Dutch Building Materials Decree as this is the only legislation available to make such an environmental judgement. A concise test has been applied to assess crucial aspects of leaching for different production mixes. Also concluded is that results from the CEN TC 154 test are different from more elaborate characterisation tests. Alternative compliance tests that do give consistent results with the more elaborate characterisation tests are available.

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