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Title:
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Environmental criteria for cement based products ECRICEM Phase I: Ordinary Portland Cements (executive summary included)
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Author(s):
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Sloot, H.A. van der; Hoede, D.; Rietra, R.P.J.J.; Stenger, R.; Lang, Th.; Schneider, M.; Spanka, G.; Stoltenberg-Hansson, A.; Lerat, A.
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Published by:
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Publication date:
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ECN
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1-12-2001
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ECN report number:
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Document type:
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ECN-C--01-069
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ECN publication
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Number of pages:
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Full text:
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228
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Download PDF
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Abstract:
Regulations such as the European Construction Products Directive (CPD)or national Drinking Water Standards contain provisions to exclude or
minimise adverse effects on environment or public hygiene through the
use of construction materials. The assessment of the "environmental
quality" of construction products such as cement and cernentitious products
is usually based on the determination of their leaching characteristics,
e.g. the potential release of constituents such as trace elements (heavy
metals) or organic compounds to the environment when the products get
in direct contact with water or soil. The report on hand presents the
results of the first part of a more comprehensive study with the following
main objectives:
- To support and facilitate the environmentally sound use of alternative
fuels and raw materials (derived from various waste streams) in cement
and concrete production.
- To support the reuse/recycling of construction debris (demolished
concrete) in construction projects, e.g. as aggregates in new concrete,
as fill materials in road construction, or others.
- To develop and propose environmental quality criteria and control
procedures for cements and cement based products.
The study was carried out by a project team consisting of scientific
research institutions (Energy research Centre for the Netherlands -
ECN, Forschungsinstitut der Zementindustrie Germany -VDZ) and members
of the cement industry (Holcim Group Support Ltd., Ciments d?obourg,
Norcem A.S.). Part I of the project is focussing on the leaching behaviour
of Ordinary Portland cements (OPC). Ten commercial cements were selected
covering a wide range of trace element compositions, and two cements
with artificially increased trace element contents were produced in
a specific pilot installation in addition. After detailed chemical and
physical characterisation of the test cements, a series of different
leaching tests was applied on standard mortar samples in order to systematically
characterise their leaching behaviour. Geochemical modelling supported
the development of model predictions of the long term release of trace
elements under various exposure scenarios. Selected major conclusions
of the study so far are:
- The pH dependence test is the test procedure best suited to characterise
the generic leaching behaviour of trace elements in cement based products,
and thus should form the basis for release assessments under different
exposure scenarios.
- There are significant differences in the generic leaching characteristics
of various groups of trace elements (e.g. "regular" metals, "oxyanions",
and metals forming soluble salts).
- In general, there is no systematic correlation between the total
contents of trace elements in cement and cement mortars, and the leaching
rates.
- For some elements such as chromium, arsenic or untimony occurring
as "oxyanions", elevated concentrations in cements may lead to increased
leaching rates under specific test conditions.
- However, zinc contents of up to 0.2 o/o in cement are not expected
to have a detrimental effect even under worst case scenarios.
- Chromium and aluminium require more systematic investigations due
to their specific behaviour and response to changing pH conditions under
different exposure scenarios.
- In certain life cycle stages of concrete (recycling or disposal),
carbonation of small particle size fractions may play an important role
in the release of trace elements.
- Test procedures have to be carefully adapted to the application
and exposure scenarios under consideration. Slightly modified "compliance
tests" are proposed to allow predicitions of the long term leaching
behaviour of trace elements in different applications.
Part II of the project wil1 mainly focus on composite cements (with
blast furnace slag, fly ash or natura1 pozzolans) and construction debris.
Using available test data model predictions of trace element release
based on test results lor different exposure and utilisation scenarios
will be verified in selected field applications. Selected ecotoxicological
tests on mortar leachates will complement the work program.
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