Preliminary Conclusions and Recommendations

Leaching from cement-based materials is far more systematic than commonly believed based on single step leaching tests.

Harmonisation of testing of monolithic materials from construction for environmental impact evaluation and assessment of treatment efficiency is badly needed.

A limited number of leaching tests can provide the crucial answers needed to assess long-term impact. For monolithic materials the combination of pH dependence test and a form of tank test is suitable.

A hierarchy in testing as well as a hierarchy in modelling can be adopted to lessen the burden of testing for industry and to make available judgement tools for decision makers with more science background than currently used.

Blended cements based on slag feature low Cr VI leachability resulting from the inherent reducing properties of slag.

For the time frame of service life it is not expected that any problems will arise apart from a few rather exceptional cases.

Chemical speciation using mineral solubility, sorption and organic matter interactions provides identification of release controlling minerals and similarities amongst widely different materials.
Understanding chemical speciation provides insights for system improvement and enhances long-term release prediction for many constituents of concern.

The proposed hierarchy in testing provides the necessary detail required by regulators and developers of treatment techniques. It also provides for cost effective verification and QC testing.

The approach developed for inorganic contaminants is equally relevant for organic contaminants and natural radionuclides.

To address the complex issue of environmental impact evaluation of long term behaviour, too simple approaches lead to poor management decisions.

In the CPD only service life is addressed for the CE marking. The main focus however for acceptability of alternative fuels and alternative raw materials for cement production will be on the reuse stage as unbound material (aggregate) or in case of disposal as inert waste. Leaching of, in particular oxyanions (Mo, V, Sb, As, Se) from mortars is most sensitive from size reduced material after carbonation.

For compliance and QC it is recommended to apply the first fractions of the tank test. This ensures proper compatibility with the more elaborate characterisation methods used as basis for scenario modelling, product improvement and limit setting.

Spin-off
New geochemical prediction tools for cement mortar chemistry addressing pore water chemistry.

Database/expert system for addressing release from construction materials by leaching now available.

< Back

Top of page

© Copyright 2003 by ECOserve