Page 376 - New Trends in Eco efficient and Recycled Concrete
P. 376

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
   371   372   373   374   375   376   377   378   379   380   381