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Lucerne – Researchers at the Lucerne University of Applied Sciences and Arts have investigated the load-bearing capacity of recycled concrete made using discarded mixed granulate. They have found that this is much more robust than had been assumed. The associated standards in Switzerland will now be adapted as a result.

Each year, around 40 million tons of gravel and sand are used to manufacture concrete in Switzerland, the Lucerne University of Applied Sciences and Arts (HSLU) revealed in a press release. In an effort to reduce these volumes, concrete from demolished buildings can be reused. Until now, recycled concrete has above all been made using demolition material that has been carefully sorted.

In the context of an initiative with the City of Zurich, the HSLU has now investigated the load-bearing capacity of recycled concrete made using demolition waste that has not been as meticulously sorted. Experiments on the HSLU campus in Horw LU have shown that while the quality of the manufactured concrete is lower than if the demolition material has been carefully sorted, it is nonetheless more robust than had previously been assumed: “the punching load capacity of plates to which mixed granulate has been added is around 5 percent lower than of those made with non-recycled material – however, the disparity is significantly smaller than is set out in the standards,” explained Albin Kenel, Head of the Institute of Civil Engineering at the HSLU.

On the basis of these research results, amendments will be made to the fact sheet of the Swiss Society of Engineers and Architects (SIA) by 2020. “This would then pave the way for more efficient use of mixed granulate in building construction,” explained the HSLU.

Armin Grieder from the City of Zurich’s Office for Building Construction is excited about the research results: “The City of Zurich is very interested in using recycled concrete made from mixed demolition waste in its construction. We see great potential to reduce the mountains of waste that otherwise result from the demolition of buildings.”