Field: Construction and demolition waste, Damage-reducing technique
Global Technical function: Sensing, Separating
Technical Function Unit: Mixing, Segregating, Strategic planning
Techniques: Hyperspectral imaging system
Geographic Area: Netherlands


Construction and demolition waste (C&DW) are often used as road foundation material as recycling into new building products requires materials of high and consistent quality. For instance, end of life (EoL) concrete from C&DW can be used for making new concrete provided that clean aggregates are produced using advanced processes to separate them into pure fractions. This requires a sophisticated method to classify the particles of different sizes correctly. At present, there are a few techniques available for concrete recycling, but being very energy intensive they cannot be considered as damage-reducing techniques or competitive in economic and environmental terms.

C2CA – Advanced Technologies for the Production of Cement and Clean Aggregates from Construction and Demolition Waste – is an on-going project with the ultimate goal to recycle EoL concrete into high-value applications such as clean aggregates and new concrete. The 14 project partners are taking a system approach to the recycling process to achieve this goal, in combination with the further development of some innovative technologies.

The recycling process in question starts with a quality control to assess the waste composition before the components are separated. The use of advanced separation and sensor technologies will assure correctness. The sensors are currently under development; one sensor is using a hyperspectral imaging system for concrete composition recognition, and the other is a laser sensor for reliable identification of materials and accurate characterisation of the physical properties of the material. The laser based sensor still needs further research, but the basic concept is that a laser beam will hit the material, causing extremely rapid heating under which the material will form plasma. According to the behaviour of the material, it can be classified in a very precise way.

The classification of the finer particles of C&DW is normally complex at the typical moisture content of this material. The solution is found in the ADR (Advanced Dry Recovery) separating technology, developed and patented by the project-coordinating Delft University of Technology in the Netherlands. The combination of sensing technologies (laser and hyperspectral) with advanced sorting technologies (ADR) is expected to improve the overall efficiency of material identification and separation to ensure that all EoL concrete components can be fully recycled. This technology has been well proven for classification in different sectors and is mostly used for recycling of bottom ash from municipal waste incinerators. The application of ADR to concrete separation is currently under development.

The next step in the recycling process will use a breaking and sorting technology for segregating silica and calcium into isolated fractions. The smaller calcium-rich fraction is converted into new binding agents by thermal processing and finally, new mortar will be produced by mixing the binding agent with the aggregate.

So far, the project is in line with the stated objectives: Two Dutch towers have been demolished, where a new dismantling and demolition approach has been tested.  The results from the project will hopefully also give input to the strategic planning process of policy makers, as they will be used to determine which kinds of strategies and policies are most effective to facilitate an efficient transition towards optimal value recovery from construction and demolition waste treatment and sustainable building.

The project is funded by the Seventh Framework Programme of the European Commission
(FP7) which is a grant funding programme.. As the project is still running and its final results will not be presented until 2014, the technology readiness level is currently estimated to be 3 on the TRL scale, according to the scope of the seventh framework programme, which provides public grant partial funding for R&D.