Concrete from Recycled Aggregates & Other Materials

An EU-funded project has developed guidelines for making concrete from recycled ingredients.  The guidelines are based on tests of recycled concrete, steel recovered from waste tyres and natural fibres from sisal.

• The production of concrete consumes large amounts of raw materials and is estimated to be responsible for around 10 % of all human-sourced emissions of greenhouse gases.
• Concrete from demolished buildings and structures also generates a large amount of waste each year.

Standard concrete used for houses, office buildings and other structures is a mix of water, cement and aggregates, such as sand, gravel or crushed stone.  Industrial steel fibres are sometimes added in a class of materials generally referred to as ‘fibre-reinforced concrete’.

• Recycled substitutes could be used to replace some of these ingredients and make concrete production more sustainable on a number of different levels.

The EU-funded project ENCORE has demonstrated that sustainable substitutes could be used in the place of aggregates and fibres.

• The project has produced three model guidelines on the technical standards for using recycled concrete, steel from waste tyres and natural fibres obtained from plants, such as sisal.
• These model guidelines are presented as recommendations for the construction industry on how to produce, process and mix concrete with recycled ingredients.
• The guidelines are presented as a possible annex to the International Federation for Concrete’s ‘Model Code for Concrete Structures’ for field applications.

During the ENCORE project different combinations of recycled ingredients were tested.  Ingredients included waste concrete, steel recovered from old tyres, fly ash left over from coal combustion and natural fibres from sisal, a type of agave plant.

• The products were tested for durability, strength and other important mechanical properties needed to ensure their performance matched that of standard concrete.
• Waste concrete was crushed to obtain recycled aggregates.  The recycled aggregates were then used to partially or totally replace those normally incorporated in regular concrete.
• Recycled steel fibres from waste tyres were used to replace industrial fibres used for fibre-reinforced concrete.
• Natural fibres were obtained through sustainable processes from sisal.  The natural fibres were used to reinforce mortars and as activators of the material’s self-healing capacity.

ENCORE developed production protocols for concrete produced using these recycled and natural ingredients, as well as design rules for the final concrete products.

With the end of the ENCORE project,  new EU-funded project called SUPERCONCRETE has been undertaken.  The SUPERCONCRETE project addresses the subject of improving sustainability in concrete production and aims to further develop ENCORE’s research and disseminate the information to engineers, concrete technologists and decision makers.

Source: EU Research & Innovation