5 Concrete constituents as example for the release of dangerous substances
5.5 Mandate M 125 – Aggregates
5.5.4 Recycled aggregates
According to the definition in DIN EN 12620, recycled aggregates consist of processed inorganic material previously used as building material [59].
The European Waste Catalogue lists individual materials that are used as recycled aggregates as waste [67]15. The table below provides an overview of the wastes listed in the European Waste Catalogue that can be used as recycled aggregates.
Table 16: EWC codes for wastes listed in the European Waste Catalogue that can be used as recycled aggregates [67]
Aggregate EWC Code Waste type
10 13 14 Waste concrete and concrete sludge from the manufacture of cement, limes and plaster and articles and products made from them
17 01 01 Concrete from construction and demolition waste 17 01 02 Bricks from construction and demolition waste 17 01 03 Tiles and ceramics from construction and
demolition waste Recycled aggregates
17 01 07 Mixtures of concrete, bricks, tiles and ceramics other than those mentioned in 17 01 06
The use of recycled aggregates for manufacturing concrete and mortar is regarded as waste recycling, which in Germany is subject to specific requirements made by the German Kreislaufwirtschafts- und Abfallgesetz – KrW-/AbfG (' Closed Substance Cycle Waste
15 When classifying aggregates as waste, it needs to be ensured that the definition according to Art. 1 a) of the Waste Framework Directive 75/442/EEC is met, whereby wastes are defined as any substance or object which the holder discards or intends or is required to discard [70].
Management Act'). For instance, Section 5, Paragraph 3 KrW-/AbfG states that the recycling of wastes should not impair the well-being of the general public, and in particular there should be no accumulation of pollutants in the cycle of reusable materials [19]. This means that requirements already have to be made for the content and leaching of dangerous substances for the constituent material "recycled aggregates". These requirements have been implemented in the national standard for recycled aggregates DIN 4226-100 [73]. The table below lists the limit values from Standard DIN 4226-100 for recycled aggregates. They accord with the Z2 values from LAGA-Mitteilung 20 for construction and demolition waste (see Annex A6) [27]. As leaching methods, the standard specifies the modified method for the batch test provided by LAGA-Mitteilung 20 [73].
Table 17: Limit values for recycled aggregates according to DIN 4226-100 [73]
Property Maximum value
Leachate
pH-value 12.5 a
Electrical conductivity 3000 µS/cm a
Chloride 150 mg/l
Sulphate 600 mg/l
Arsenic 50 µg/l
Lead 100 µg/l
Cadmium 5 µg/l
Chromium, total 100 µg/l
Copper 200 µg/l
Nickel 100 µg/l
Mercury 2 µg/l
Zinc 400 µg/l
Phenol index 100 µg/l
Solid materials
Hydrocarbons (H18) 1000 mg/kg b
PAH according to EPA 75 mg/kg
EOX 10 mg/kg
PCB 1 mg/kg
a No exclusion criterion
b Exceeded values that are attributable to asphalt constituents do not represent an exclusion criterion
The IBAC study has assessed recycled aggregates that comply with the limit values according to DIN 4226-100 as being environmentally safe [26].
In Germany, recycled aggregates not covered by DIN 4226-100 require a national technical approval for application areas where safety aspects are relevant. To prove environmental compatibility here, the results of batch tests conducted on the original material must comply with the Z2 classification values for building rubble provided by LAGA-Mitteilung 20 [27].
Furthermore, in the long-term static test the test specimen produced with recycled concrete must not exceed the insignificance thresholds ("no effect levels") of the DIBt Guideline
Soil/Groundwater [20]. If, however, the insignificance thresholds ("no effect levels") of the original substance are already complied with in the batch test, it is possible to dispense with the long-term static test.
The Technical Rules of the LAGA specify further requirements in addition to the classification values. For instance, it is necessary to estimate the contamination caused when rebuilding, refurbishing or demolishing construction works. Based on these findings, it shall be determined whether other analytical examinations are required in addition to the Z 2 values for building rubble. Building rubble with harmful contaminants must be cleaned in suitable treatment plants. Furthermore, only 5 % vol. of the non-mineral constituents may be made up of foreign matter. Building rubble with a higher proportion of foreign matter may not be used in this composition [27]. Standard DIN 4226-100 specifies that the foreign matter content of the non-mineral material shall be between 0.2 and 1 % by mass depending on the type of aggregate [73].
In addition to the German standard for recycled aggregates [73], the Dutch Building Materials Decree [25] provides limit values for stony material that can be drawn upon for assessing the environmental compatibility of recycled aggregates. Annex 2 of the Dutch Building Decree lists limit values for the content and immission of contaminants in stony materials. The immission values are calculated from emission values determined in an elution method which are then converted into the immission values [25] (see also Section 5.3.3).
Recommendations for the content/release of dangerous substances from recycled aggregates
The source of the recycled aggregates should be labelled. The use of recycled aggregates from suspected contamination sites should be excluded in the harmonised product standards. Recycled aggregates from sites not suspected of being contaminated should be examined in terms of the leaching of inorganic and organic parameters. The parameters being examined should be based on the Technical Rules of the LAGA for building rubble (Z 2 values) [27], the DIN 4226-100 for recycled aggregates [73] and the Dutch Building Materials Decree [25].
To exclude harmful contaminants, the proportion of foreign matter in non-mineral material should be specified. Likewise, guidelines here can be found in the Technical Rules of the LAGA for building rubble [27] and DIN 4226-100 [73].
It still needs to be examined whether recycled aggregates that comply with the leachate values according to DIN 4226-100 in the batch test also comply with the insignificance thresholds ("no effect levels") in the long-term static test with concrete test specimens made of recycled aggregates.
5.5.5 Overview of the recommendations for the second standard generation for aggregates
The table below provides a summary of the studies on the environmental compatibility of aggregates described in the previous section and summarises the recommendations for revising the technical specifications.
Table 18: Overview of the recommendations for revising the technical specifications for aggregates
Recommendations for the second standard generation
M 125: Aggregates
Release of heavy metals:
Natural aggregates
Differing statements on the heavy metal content of natural stone relative to uncontaminated soil and the lithosphere
General discussion necessary as to whether additional requirements should be made for natural stone in terms of leaching of heavy metals
Manufactured (artificial) aggregates:
Possible to have increased heavy metal content.
Batch tests to DIN 38414-S4 have shown that the insignificance thresholds ("no effect levels") of the DIBt Guideline are complied with. Not possible to make any statements about chromates and cadmium.
No results from long-term static tests for concrete test specimens with the slags used.
When using mineral materials that are by-products of industrial processes, the content and leaching of heavy metals should be
examined on the original material. The range of parameters should be based on the Z 2 values of the respective waste-specific regulations of LAGA.
There is a need to examine whether concrete produced with manufactured aggregates also complies with the insignificance thresholds ("no effect levels") of the DIBt Guideline
Soil/Groundwater.
There is a need to examine whether it is sufficient to determine the content if the release can be inferred from the content.
DIN EN 12620 DIN EN 13055-1
Heavyweight aggregates:
Heavy metal content very high in comparison with normal and lightweight aggregates.
No results available from leaching tests.
Necessary to continue examining the environmental compatibility through leaching tests.
Harmonised product standards
Content/Release of dangerous substances
Recommendations for the second standard generation
M 125: Aggregates
Lightweight aggregates:
With batch tests to DIN 38414-S4 for bricks and expanded clay, the insignificance thresholds ("no effect levels") according to the DIBt Guideline were exceed for a series of heavy metals. There have been no
examinations of leaching using long-term static tests.
When using mineral waste such as furnace sand (processed coal bottom ash), the Z2 classification values of the respective waste-specific Technical Rules of the Working Group of the German Länder on Waste Issues (LAGA) should be complied with for the original material (content in solid materials and leachate).
There is a need for further examination as only a few results exist from leaching tests. The test results should be assessed using the
insignificance thresholds ("no effect levels") of the DIBt Guideline.
When using waste glass, environmentally dubious waste glass, such as lead glass, should be excluded.
DIN EN 12620 DIN EN 13055-1
Recycled aggregates: Indicate the source of the recycled aggregates.
The use of recycled aggregates from suspected contamination sites should be excluded.
Recycled aggregates from sites not suspected of being contaminated should be examined in terms of the leaching of inorganic and organic parameters. The parameters being examined should be based on the Technical Rules of the LAGA for building rubble (Z 2 values), the DIN 4226-100 for recycled aggregates and the Dutch Building Materials Decree.
The proportion of foreign matter in non-mineral material should be determined. Guidelines here can be found in the Technical Rules of the LAGA for building rubble and DIN 4226-100.
There is still the need to examine whether recycled aggregates that comply with the leachate values according to DIN 4226-100 in the batch test also comply with the
insignificance thresholds ("no effect levels") in the long-term static test with concrete test specimens made of recycled aggregates.