Recycled concrete for the 2012 Olympic Village

(UK) -- Mention the word demolition to almost anyone and the picture that instantly comes to mind is a vision of a building being blown up and collapsing to the ground. Many people have stated that they would love to push the button, to detonate the explosive devices which bring a disused building to the ground. In many cases what comes down, must go up and we are seeing many old buildings being demolished to make way for future development, often as part of a regeneration project.

For companies who over many years have built their business around the demolition of buildings, the demolition sector is now far more reaching than just demolishing old buildings. Once the building is demolished the huge task of site clearance begins and in a world where consideration of the environmental impacts are high on most peoples agenda, the material residues from demolition need to be sorted for recycling purposes. This will include such materials as steel, wood, plastic, brickwork and concrete.

Most of the materials can be bulked up and transported to the appropriate recycling plants for reprocessing. Materials such as bricks and concrete can be crushed and turned into a recycled concrete aggregate product ready for reuse in the construction of new roads or buildings. Increasingly though, through advances in technological development, residues such as rubble to be recycled have to meet a very high specification for reuse in construction projects.

Crushed into different grades of recycled aggregate will determine the future usage potential of the product. Large sizes could be used as decorative rockery products in gardening whilst much finer, almost shingle like product can be used as a bedding for pipe laying or as a layer in road construction. With an increasing number of opportunities identified for the reuse of recycled aggregate, the entire demolition and construction industry is making a significant contribution to sustainable development.

Reasons Behind the Increased Focus on Recycling from Construction and Demolition Projects
In 1996, UK Government imposed a tax on all wastes going to landfill. The tax is paid on top of normal gate fees for waste being disposed in landfill and since its introduction the cost has increased on an annual basis. When first introduced, the standard rate of tax for general wastes going to landfill was £7 per tonne and £2 per tonne for inert materials. The tax is designed to encourage commercial and industrial businesses and local authorities collecting from households, to divert waste away from landfill for recycling. In April 2009, the standard rate of landfill tax increased to £40 per tonne and is scheduled to increase each year by £8 per tonne until 2013. The lower rate of tax charged upon any inert materials going to landfill such as concrete and soils, has remained relatively steady in recent years and is currently at £2.50 per tonne.

However, the weight factor alone of a bulk load of these inert materials going directly to landfill will ensure that the entire cost of disposal becomes very expensive and so even in the demolition and construction sector, diverting waste from landfill is a priority. The introduction of landfill tax has been a key driver in encouraging greater diversion of inert materials from landfill, to be used in sustainable development projects.

Following demolition and after passing through the crushing process recycled stone produced from concrete and rubble from the demolished buildings can be used for a variety of purposes.

Next time you see a demolition project in progress or pass any construction site during a build programme, it is clear to see the volume of waste being generated. If waste is not in skips, piles of rubble will be stacked high. The placing of rubble waste in skips has been a major problem for waste contractors for many years. Having worked in the waste industry, I have seen skip lorries tipped backwards with the cab of the vehicle up in the air, due to the sheer overloading of waste skips with construction site waste.

Each year, the UK generates around 330 million tonnes of waste and it is estimated that around 90 million tonnes of this is from construction and demolition wastes. This figure has remained fairly constant since 2001. Around two thirds of this waste is usually recycled or reused in land reclamation or agricultural improvement projects. Since the late 1990s there has been a steady rise in the volumes of construction waste being recycled and this has been helped with advances in technology which have led to improved crushing technology to create more widespread use of different specifications of recycled aggregates.

In recent years, the construction industry as a whole has worked hard to encourage construction project managers to place a greater focus upon recycling on site. This has led to an increase in the recycling of all inert materials from site.

Prior to the introduction of the landfill tax all construction site waste including bricks and concrete would be bulked up and transferred to a landfill site for disposal. No consideration was given to recycling. There are now stringent regulations across the sector, coupled with an increase in environmental awareness, as well as the commercial benefits in ensuring that this type of waste is now recycled. There is also greater recognition of the vast array of opportunities to use recycled aggregates within the construction process on alternative construction projects or in areas such as landscaping or home and garden DIY. Following the demolition process, together the waste concrete, bricks, masonry etc will be transformed into a recycled concrete aggregate. Recycling of aggregates has become a common process for demolition contractors.

To recycle concrete aggregate to a high standard and resalable product, it must be entirely free of other contaminants such as wood, paper, card, steel and other general waste materials. The final product must also conform to the requirements of British Standard BS 8500. The process of recycling the concrete can usually be achieved in one of two ways. Some demolition contractors will transport a crushing machine on the demolition site, whereas some contractors will prefer to transport the waste to be recycled, back to their own premises for sorting for recycling or re-use. On projects where demolition and new construction is to take place at the same location, the contractor is very likely to locate a crushing machine on site to avoid incurring additional transportation costs in taking the material back to a sorting and crushing facility. There is now very sophisticated crushing equipment available to reduce concrete to a very fine specification.

Construction and demolition contractors will look to recycle as much waste as possible from the demolished building.

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