Sampling gases at their outlet during an experiment on resuspending PCB-contaminated sediments (2010). © BRGM - Philippe Bataillard

Construction waste, a new "urban mining" resource

After developing a process to recover concrete from demolition waste, the BRGM, as a contributor to a European demonstration project, has been selected by ANDRA to take part in the development of a recycling process for concrete from nuclear plant dismantling.

While 48 million tonnes of demolition waste are produced each year in France, seven tonnes of aggregate per inhabitant are extracted from the natural environment for construction and civil engineering!

Although still marginal, recycling construction waste is a promising solution which is key to reducing pressure on natural materials and also to energy savings in particular.

"With the Ecotech Cofrage project", explains Yannick Ménard, "the BRGM piloted the development of a process that selectively releases the constituents of concrete, i.e. hydrated cement paste, sand and aggregate. Two techniques have been optimised, one involving microwave heating and the other the application of electrical pulses before selective crushing. Both have demonstrated their effectiveness as a means of recovering reusable aggregate as an ingredient of new concrete, and cement paste for clinker production". The BRGM is now involved, with the EU Hiser project, in industrial demonstrations of these technologies. With the Swiss equipment manufacturer Selfrag AG, the BRGM is working to adapt the electro-fragmentation technique to release intermixed materials like concrete, bricks, plaster, etc.

Last but not least, ANDRA (the French agency for radioactive waste management), which is facing saturation point at its storage sites for very low-level radioactive waste, has selected the Cyber project in a call for projects in view of the dismantling of nuclear power plants. "This project was initiated by the BRGM", says Yannick   Ménard, "with the aim of developing a process for the selective separation of the different constituents of the concrete. Several studies have shown that radioactivity concentrates in cement paste, and this would open the way to optimising storage of the materials on the surface, in the French context, and decontaminating the sand and aggregate. This would significantly increase the quantities of recyclable concrete waste in countries that have thresholds for the release of materials from the nuclear industry (levels of contamination below which there are no restrictions on use of the materials).

A demolition site that clearly illustrates the need for recycling construction waste. © BRGM

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