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Title:
Environmental criteria for cement based products ECRICEM Phase I: Ordinary Portland Cements (executive summary included)
 
Author(s):
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.
 
Published by: Publication date:
ECN 1-12-2001
 
ECN report number: Document type:
ECN-C--01-069 ECN publication
 
Number of pages: Full text:
228 Download PDF  (15510kB)

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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