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Leaching issues in recycled aggregate concrete 331
The high potential for recycling CDW is derived from its composition, being
feasible the reutilisation of aggregates derived from CDW waste in many different
construction applications and infrastructure, such as: drainage, base or sub-base on
roads, filling of embankments and other construction projects. This high variety of
real applications is feasible due to the management processes implemented by plant
treatment managers and is, generally, inexpensive. The aim of the WFD is to pro-
vide a framework for all Member States in order to achieve an European society
with a high efficiency on exploitation of natural resources and, therefore, a capable
of building a sustainable future. In particular, Article 11.2 stipulates that ‘Member
States shall take the necessary measures designed to achieve that by 2020 a mini-
mum of 70% (by weight) of non-hazardous CDW excluding naturally occurring
material defined in category 17 05 04 in the List of Wastes shall be prepared for
reuse, recycled or undergo other material recovery’. However, as illustrated in
Fig. 12.1, the recycling percentage of CDW varies greatly between the registered
countries.
12.1.2 Assessment of potential environmental risk. Main factors
to consider
The specific properties of waste that render it hazardous are defined in Annex III of
the WFD. A given waste stream is to be considered ‘hazardous’ when it displays
one or more of the listed hazardous properties (Article 3). Also, the WFD
encourages Member States to collect separately ‘hazardous compounds from waste
streams if necessary to achieve environmentally sound management’.
The most extensively researched material used in the production of recycled
aggregate concrete is recycled aggregates from CDW, that is, fine and coarse debris
from demolition sites. Previous works have demonstrated that recycled aggregate
possess suitable physical and geotechnical properties for be reused during its second
cycle of life as recycled concrete. However, it is important to note that the potential
presence of hazardous components from CDW requires caution during its manage-
ment in the plant. So, the reduction of these harmful compounds must be a priority
through the selection of the inert components of the aggregates for later use.
Before granular recycled concrete aggregate (RCA) can be reused in construc-
tion works, the material should be tested for potential leaching of contaminants. For
this purpose, a number of EU Member States will adopt, or have already adopted,
regulations that limit the leaching of contaminants from construction products (e.g.,
Dutch Soil Quality Decree, EU Construction Product Regulation). In such regula-
tions, leaching as measured with a laboratory test is compared to a pass/fail crite-
rion. However, many such regulations do not yet account for the observation that
any leaching test result needs extrapolation to the real behaviour of the material in
various field scenarios.
The assessment of the environmental risk resulting from the application of con-
struction materials in different scenarios (landfill, embankments, slopes or sub-base