Each year, the construction sector of North Carolina produces nearly 37 million tons of waste. In order to valorize them, the concrete industry is putting in place means to recycle deconstruction concrete, and in particular by reusing it in the manufacture of new concrete.
In the 2000s, the construction industry noted that there was a lack of recovery of deconstruction concrete in NC, falling behind other states.
Demolition of a building
Several reasons pushed the sector to react:
- The increase in waste flow linked in particular to the large number of old buildings reaching the end of their life (built in the 1950s during the post-war period) as well as the increase in landfill costs. Demolition concrete waste represents 3 million tons per year
- The problem of transporting natural resources used to produce concrete (limestone, clay, etc.), quarries sometimes being too far from cities and the opening of new quarries resulting from long and complex processes. The use of construction and cemolition waste is advantageous because it is generated within cities like Summerfield and others, just like new construction sites that need raw materials. Transport is reduced, as are greenhouse gas emissions
- Finally, concrete is also lagging behind the recycling of other materials (steel, bitumen, etc.), which has been in place for years.
- Concrete waste produced by concrete manufacturing processes (waste of fresh concrete, hardened concrete, manufacturing scrap, concrete returned from construction sites, etc.), which can be reintroduced into the manufacture of new concrete
- Concrete waste from deconstruction, and this is where most of the work takes place
- either directly on site using suitable equipment
- either the concrete rubble is collected then sorted on a dedicated site belonging to specialized companies
- https://www.cement.org/docs/default-source/ga-pdfs/cement-industry-by-state-2015/north-carolina.pdf
- https://www.ncconstructionnews.com/
- https://junkremovalvancouverbc.com/2023/12/02/the-importance-of-recycling-and-its-impact-on-the-environment/
- https://www.dumpsterrentalnearmesummerfieldnc.com/
- https://junkremovalvancouverbc.com/2023/05/31/sustainability-and-pollution-issues-in-the-usa/
How is waste from the construction sector decomposed
90% of this waste comes from the rehabilitation and deconstruction of buildings; some are inert waste (rubble, concrete, tiles, bricks, etc.); some are are non-hazardous waste (wood, plastic, scrap metal, plaster, etc.); only 2% is hazardous waste (asbestos waste, solvents, etc.), and they cannot use regular dumpster rental services.
Among this inert waste, we can distinguish two ways of recycling and recovering concrete:
The case of waste recovery by the cement industry
Cement industry
The cement industry of North Carolina also has an important role to play in the recovery of waste from the sector. In fact, energy and material recovery can be achieved during the cement manufacturing stages.
In terms of energy recovery, the cement industry’s objective is to achieve a rate of 50% substitution of fossil fuels in 2025. The substitute fuels used are called Solid Recovered Fuels. These are for example furniture, wood, fabrics, plastics, etc.
In terms of material valorization, the cement industry saves raw materials (limestone, clay, gypsum) by replacing them with minerals from other industries such as blast furnace slag from the steel industry or fly ash from coal-fired thermal power plants.
Demolition waste
Currently, 80% of deconstruction concrete is already used in various road applications (subgrade layers, road base layers, etc.) and 20% of this concrete is sent to Inert waste storage facilities. However, the recovery of deconstruction concrete remains very low in buildings. Thus, one of the main challenges is to show that recycled concrete can be used in a building without changing the implementation methods used with traditional concrete.
It happens that certain rural sites are too far from treatment facilities for the recovery of this waste to be economically viable. This is due to the fact that the networks of construction waste sorting platforms are not distributed equitably across the territory. Thus, a more optimal network would make it possible to reduce the transport of waste and thus the environmental impact, but also the landfilling of waste.
What does the recycling of this deconstruction concrete involve
This involves recycling demolition concrete to make aggregates most of the time, by grinding the deconstruction rubble more or less finely, depending on the desired result. These aggregates are called recycled concrete aggregates.
You should know that in North Carolina, the need for aggregates per year is 55 million tons and that only 28% is covered by the reuse of recycled aggregates.
It is also possible to grind the rubble more finely to obtain sand, but it is the aggregates which are most often produced, because they are quite simply the majority in the manufacture of concrete. The aggregates, like the fine elements, will be reused in the manufacture of new concrete. These recycled aggregates and sand have the advantage of being closer to the places of their consumption than naturally extracted aggregates or sand. This helps reduce costs and CO2 emissions in terms of transport.
The different stages of concrete valorization
The first step in recovering waste from the deconstruction of a building is to sort the rubble produced.
Depending on the quantity of rubble to be sorted, sorting can be done:
It is preferable to favor deconstruction over demolition without sorting materials. Indeed, sorting is essential to separate the concrete from the other materials present in the rubble (plaster, reinforcements, etc.). This sorting must be carried out during deconstruction and then during treatment of the waste on the waste treatment platforms, verifying that there is no presence of contaminants.
Sorting techniques are becoming more and more efficient and are spreading on construction sites, even if some still prefer to quickly demolish old buildings without sorting the rubble, which alters the quality of the 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 correct channel for recycling. The concrete is crushed, scrapped and carefully examined. Additional treatments can be performed if necessary. In the end, we obtain 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 serve as an underlay for roads or for earthworks, or it will will use it for the manufacture of new concrete.
Materials of lower quality can be used for road underlays (non-toxic industrial waste, degraded natural aggregates, etc.). So it may be interesting to devote more of this waste to the manufacture of new concrete, instead of using dumpster rentals to send them to the nearest landfill.
