Recycling concrete
The cement industry also has an important role to play in the recovery of the sector's waste. Indeed, energy and material recovery can be achieved during the cement manufacturing stages. In terms of energy recovery , the objective of the cement industry is to achieve a rate of 50% substitution of fossil fuels by 2025. The substitution fuels used are called Solid Recovered Fuels (SRC) . These are, for example, furniture, wood, fabrics, plastics, etc.récupération de béton In terms of material recovery , the cement industry saves raw materials (limestone, clay, gypsum) by replacing them with minerals from other industries such as slag from blast furnaces in the steel industry or fly ash from coal-fired power plants. Currently, 80% of deconstruction concrete is already recovered in various road applications (capping layers, pavement base layers, etc.) and 20% of this concrete is transported to Inert Waste Storage Facilities (ISDI) . On the other hand, the recovery of deconstruction concrete remains very low in buildings. Thus, one of the main challenges is to show that it is possible to use recycled concrete in a building without modifying the implementation methods used with traditional concrete. What is the recycling of this deconstruction concrete? This involves recycling the demolition concrete in order to make aggregates most of the time, by crushing the deconstruction rubble more or less finely, depending on the desired result. These aggregates are called recycled concrete aggregates (GBR) . You should know that in France, the need for aggregates per year is 435 million tonnes and that only 28% is covered by the reuse of recycled aggregates (1) . The different stages of concrete recovery The first step in recovering waste from the deconstruction of a building is to sort the rubble produced . Depending on the amount of rubble to be sorted, sorting can be done: either directly on site using suitable machinery; or the concrete rubble is collected and then sorted on a dedicated site belonging to specialized companies. It is preferable to favor deconstruction over demolition without sorting the materials. Indeed, sorting is essential to separate the concrete from the other materials present in the rubble (plaster, reinforcement, etc.). This sorting must be carried out during deconstruction and then during waste treatment on waste treatment platforms, checking that there is no presence of contaminants. Sorting techniques are increasingly efficient and are spreading on construction sites, even if some still prefer to quickly demolish old buildings without sorting the rubble, which affects the quality of recycled concrete. In addition, a waste diagnosis before deconstruction can optimize the quality of rubble sorting. Once the waste is sorted, each type of waste is sent to the right channel for recycling. The concrete is crushed, scraped and examined carefully. Additional treatments can be carried out if necessary. In the end, we obtain a concrete in the form of rubble. A final check is carried out to verify that there are no signs of pollution, then the fate of the concrete for its second life is decided: either it will be used as an underlayment for roads or for earthworks , or we will use it for the manufacture of new concretes .