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'Concrete' solutions

11/03/2013

The European Union's construction sector faces a testing target. Under the EU Waste Framework Directive (2008/98/EC), it must, by 2020, reuse or recycle at least 70% by weight of non-hazardous construction and demolition waste.

In some countries, such as Belgium, Germany and the Netherlands, says Dr Kris Broos of Belgian sustainable development research institute VITO, the target is already being exceeded. For the EU construction sector as a whole, however, a 70% reuse and recycling rate is feasible but will “definitely not be easy”.

Fortunately, research is being done into the reuse and recycling of construction and demolition waste, 380 million tons of which is produced in the EU each year - more than 30% of total EU waste. IRCOW, a project supported by the EU's Seventh Framework Programme, is analysing through five case studies best practice in management of construction and demolition waste. VITO is a partner in IRCOW (Innovative Strategies for High-Grade Material Recovery from Construction and Demolition Waste).

IRCOW started in January 2011, and will run until the end of 2013. The case studies cover a wide range of situations commonly faced by the construction industry. They deal with:

  • Selective demolition of a derelict industrial building in Bilbao, Spain;
  • Selective demolition of a mainly wood-built former school in Sweden;
  • Treatment of hazardous material (in particular asbestos) from a demolition site in Poland;
  • Construction of an office building in Madrid using recovered and recycled materials;
  • Use of new concrete products made from recovered demolition waste for an industrial building in the Port of Antwerp, Belgium.

So far, results have been promising. The case studies in Bilbao and Poland have been completed. In Bilbao, a building dating from the 1970s with a concrete structure and a brick facade was cleared and demolished. The clearing operations involved the sorting of different materials, such as wood waste, metal frames, plastics and hazardous waste. The different types of waste were treated appropriately, with hazardous waste, such as asbestos, transported off-site for specialist treatment.

The building was then demolished. Steel reinforcing bars were separated from the waste concrete and bricks, which were crushed, generating mounds of recycled aggregate. This aggregate was used as the basis for new concrete. Four types of concrete, using different combinations of recycled materials, were prepared and tested. It was found that the recycled concrete could be used safely for foundations and concrete slabs.

The Polish case studied the onsite treatment of hazardous demolition waste, in particular asbestos. Microwave Thermal Treatment, developed by Polish company ATON-HT, was applied to hazardous waste. The result is that asbestos is, in effect, burned out of the waste, and the hazardous material is converted into a non-hazardous material. “The product that resulted was neutral for the environment and could be reused as a construction material,” says Izabela Ratman-Kłosińska of project partner the "Institute for Ecology of Industrial Areas".

The Swedish case study has also been completed as far as was possible. It was decided not to demolish the old school building for economic reasons. Nevertheless, says David Palm of Swedish partner IVL Swedish Environmental Research Institute, a full inventory of building parts was completed, showing what could be reused and what could be recycled. “For the directly reusable items there is a clear environmental benefit,” Palm says. This is particularly the case for steel parts.

The remaining case studies are underway (Port of Antwerp) or starting (Madrid). In Antwerp, concrete using recycled aggregate is being used to create concrete parts for a new waste facility. The performance of the concrete will be monitored in real world conditions.

The recycled aggregate comes from demolished buildings near the construction site. In particular, the project has shown that cellular, or aerated concrete (commonly known as breeze blocks, or Beton blocks) can be recycled. Previously, this was not recyclable into concrete because it is lightweight and weakens recycled aggregates. However, IRCOW has been able to separate this waste from other concrete waste and recycle it into a material that can be used for insulation and for flooring screeds. “We took a contaminant from the waste stream and turned it into a product,” VITO's Kris Broos says.

Although not finished, the IRCOW project has shown so far that there is substantial scope either for the increased reuse of construction waste (for example, doors and windows), or for its recycling into low-grade applications, such as aggregates for building foundations and roads. The main environmental benefits are avoided use of raw materials, and avoidance of waste being sent to landfill. In Flanders, Belgium, for example, 10 million tons of aggregates is recycled annually, says Broos. “That's a lot of virgin material that you don't have to go and excavate”. IRCOW has yet to carry out a full environmental analysis, also covering issues such as energy use and emissions.

Reuse and recycling of construction waste can also be cost effective, especially where there is infrastructure to manage the waste. D’Appolonia, an engineering consulting company that is also an IRCOW partner, gives the example of Flanders, where construction and demolition waste “is collected from the demolition market and is conferred to waste collection/processing centres, which are distributed over the territory. Hereby the secondary raw material is provided to construction companies”. However, in countries lacking such infrastructure, there might still be a cost incentive to use primary raw materials, unless “taxes or other charging systems are implemented due to scarcity of primary raw materials”.

The main obstacles to greater reuse and recycling of construction waste, according to IRCOW, are the technically acceptable use of recycled materials for higher-grade applications, and trust in products made from recycled materials.

Amaia Lisbona of Spain's Tecnalia, the project coordinator, says that IRCOW has been looking at wood-polymer composites, which could be used for decking or flooring, or window or door frames, as an example of recycling of material for higher-grade use. Wood-polymer composites can absorb water into the wood fibres, but this can be solved by introduction of other materials from construction waste, such as gypsum, Lisbona says. IRCOW has also shown that higher grades of concrete can be produced from recycled materials.

To ensure that recycled products can be trusted, certification schemes might be needed, or recycled materials, such as aggregates in concrete, will need to be incorporated into existing standards. VITO's Kris Broos, however, says that increasing the proportion of recycled materials should be a process, not a sudden leap. “We believe very much in a stepwise approach. The market might not follow if it is too radical,” Broos says.

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