Concrete recycling

Large pieces can be used as bricks or slabs, or incorporated with new concrete into structures, a material called urbanite.

[5] It is estimated that in 2018 the European Union generated 371,910 thousand tons of mineral waste from construction and demolition, and close to 4% of this quantity is considered hazardous.

[6] In the context of a circular economy the most efficient way to utilise concrete after fulfilling its initial purpose may not be clear.

Hollow core concrete slabs are easy to dismantle and the span is normally constant, making them good for reuse.

Studies show that back-building and remounting plans for building units (i.e., re-use of pre-fabricated concrete) is an alternative for a kind of construction which protects resources and saves energy.

[9] The viability of this alternative has to be studied as the logistics associated with transporting heavy pieces of concrete can impact the operation financially and also increase the carbon footprint of the project.

Concrete debris is routinely shipped to landfills for disposal, but recycling is increasing due to improved environmental awareness, changing regulation/laws and economic benefits.

It is estimated that even near complete recovery of concrete from construction and demolition waste will only supply about 20% of total aggregate needs in the developed world.

[4] The path towards circularity goes beyond concrete technology itself, depending on multilateral advances in the cement industry, research and development of alternative materials, building design and management, and demolition as well as conscious use of spaces in urban areas to reduce consumption.

[16] Large pieces of concrete rubble (urbanite) can be used in walls as building stones,[3] as slabs in walkways,[2] or as riprap revetments[17] to reduce stream bank erosion.

[18] Ecology blocks (eco-blocks) are made from recycled concrete and used for retaining walls and other temporary structures, and have also been used for hostile architecture.

Sub-base gravel is laid as the lowest layer in a road, with fresh concrete or asphalt poured over it.

Finally, the dissociation of calcium oxide in water in the soil increases electrolyte concentrations and pH, and hence SiO2 and Al2O3 dissolve more readily and promotes pozzolanic reactions.

Materials such as Portland cement, fly ash, and lime are already used extensively to amend and stabilize soil, so the same concept can be extended to concrete waste, which is itself an alkali-activated mixture.

Geopolymeric binder combined with metakaolin can yield material with desired silicon, aluminum, and calcium contents.

[26] Concrete waste that is rich in alkaline calcium compounds can be used to remove and recover various elements from an aqueous solution.

This would offer advantages over using conventional gas treatment agents because concrete waste is cheap and produced in large amounts.