Technical aspects of CDW recycling

The University of Liège (Wallonia, Belgium) is working on the technical aspects of recycling sands and aggregates from CDW. Their analyses focus on the best processes for treating CDW with regard to three points: the washing process, fragmentation, and the compressive strength and durability of mortar and concrete. The ultimate objective is to position recycled aggregates and sands as a true alternative to primary raw materials in construction.


To produce high quality CPP from recycled CDW, the University of Liège is currently analysing the best processes for treating recycled sands and aggregates. In Belgium, these materials are traditionally processed in fixed and mobile recycling plants. Those can be organised differently depending on the final material they produce and on the type of crusher, the separation systems, and the number of grinders that they use. The crusher (e.g. impact crusher, or jaw crusher) influences the materials’ particle size, which is the first essential step of the process. Tradecowall and ‘Centre Terre et Pierre’ (a research centre) are supporting the University in those tests.

Second, researchers will investigate the influence of the washing process on the chemical, physical, mineralogical and mechanical properties of the recycled sands and aggregates to further refine the treatment methods. The University will carry out comprehensive tests on samples of both washed and unwashed recycled materials provided by Tradecowall. Those lab tests will analyse chemical, physical and mineralogical characteristics.

According to research in this field and observations on site, it seems that hardened cement paste or mortar attached to aggregate plays a key role in determining the quality of recycled materials. It also has a significant impact on the behaviour of concrete mixtures from recycled materials as attached mortar displays higher porosity in recycled aggregates compared to the primary ones. In order to separate aggregates from the materials matrix, the University of Liege will test an electro-dynamic fragmentation device, initially developed for mineral recycling.

Last, but not least, researchers will assess the compressive strength and durability of mortar and concrete made from recycled sands and aggregates. Both Vicat and Prefer will be involved in this stage of the project to manufacture cement and CPP, respectively. The final products resulting from this pilot case will be used in three investments in Seraing/Belgium, Saarlouis/ Germany and the region of Moselle /France. 

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