Introduction
Mention the phrase demolition to almost any person and the image that immediately comes to mind is a vision of a building being blown up and collapsing to the ground. Plenty of people have claimed they would love to press the button, to trigger the explosive units that bring a disused building to the ground. On many occasions the thing that comes down, must go up and now we are witnessing many old properties being razed to help with making way for future development, often during a regeneration project.
For companies that over several years have built their business around the demolition of buildings, the demolition market has become much more reaching than just demolishing old buildings. As soon as the building is demolished the massive task of site clearance starts and in a world where consideration of the environmental effects are ever increasing on most peoples agenda, the material remains from demolition ought to be separated for recycling applications. This can include such products as steel, wood, plastic, brickwork and concrete.
Almost all of the materials are bulked up and sent to appropriate recycling plants for reprocessing. Products such as bricks and concrete can be crushed and turned into a recycled concrete aggregate product completely ready for reuse in the making of new roadways or buildings. Ever more though, through breakthroughs in technological development, residues like concrete to be recycled have to meet a high standard for reuse in construction projects.
When crushed, the assorted sizes of recycled aggregate will govern the future usage potential of the product. Large sizes could be utilised as ornamental rockery products in gardening whilst much finer, almost shingle like product may be used as a bedding for pipe laying or for a layer in street construction. With an increasing amount of options recognized for the reuse of recycled aggregate, the entire demolition and construction industry is making a considerable contribution to sustainable development. Following demolition of a site, many demolition contractors have expanded their service offering to include site clearance services.
Reasons Behind the Increased Concentration on Recycling from Construction and Demolition Projects
In 1996, UK Government added a tax on all waste materials going to landfill. The levy is paid out on top of standard gate fees for waste materials being disposed in landfill and since its initial release the fee has increased on an annual basis. When first introduced, the typical rate of tax for general waste materials being sent to landfill was �7 per tonne and �2 per tonne for inert substances. The levy is designed to persuade commercial and industrial companies and local authorities collecting from households, to divert waste away from landfill for recycling. In April 2009, the typical rate of landfill duty increased to �40 per tonne and is also timetabled to rise each year by �8 per tonne until 2013. The reduced level of duty incurred upon any inert materials going to landfill for example concrete and soils, has stayed relatively stable in recent years and is currently at �2.50 per tonne.
Even so, the weight factor alone of a bulk load of those inert materials going direct to landfill will ensure that the full cost of disposal becomes extremely expensive and so even in the demolition and construction arena, diverting waste from landfill is a priority.
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Next time you see a demolition project in progress or go past any construction site during a build programme, it will be very clear to see the volume of waste materials being produced. If waste isn’t in skips, heaps of rubble will probably be stacked high. The placing of construction waste in skips has been a significant problem for waste companies for quite some time. Having worked in the waste industry, I’ve seen skip trucks tipped backwards with the cab of the vehicle up in the air, a result of the sheer overloading of waste skips with building site waste.
Each and every year, the united kingdom generates around 330 million tonnes of waste material and it is estimated that around 90 million tonnes of this is coming from construction and demolition wastes. This number has remained relatively steady since 2001. Close to two thirds of this waste is generally recycled or reused in land reclamation or agricultural development projects. Ever since the later part of the 1990s there has been a steady rise in the quantities of construction waste material being recycled and this has been helped by improvements in technology that have resulted in improved crushing products to create more frequent use of varying specifications of recycled aggregates. There has been a genuine focus upon the United Kingdom construction community to encourage increased recycling of waste on site.
In recent years, the construction sector in general has worked hard to persuade construction site supervisors to place a larger focus upon recycling on site. This has triggered a growth in the recycling of inert materials from site.
Prior to the introduction of the landfill duty just about all construction site waste materials including bricks and concrete would be bulked up and moved to a landfill site for disposal. No thought was given to recycling. There are now strict limitations across the sector, coupled with an increase in environmental focus, as well as the commercial advantages in making certain that this kind of waste is now recycled. Addititionally there is greater recognition of the vast array of business opportunities to re-use recycled aggregates within the construction process on future construction projects or in arenas such as landscaping or home and garden DIY. Following the demolition process, together the waste concrete, bricks, masonry etc will likely be transformed into a recycled concrete aggregate.
To recycle concrete aggregate to a high grade and resalable product, it has to be entirely free of other contaminants such as wood, paper, card, steel and other general waste materials. The end product must conform to the requirements of British Standard BS 8500. The task of recycling the concrete can normally be achieved in one of two ways. Some demolition companies will install a crushing machine on the demolition site, whereas a lot of contractors will prefer to move the waste to be recycled, to their 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 likely to position a crushing unit on site to avoid incurring added transportation costs in taking the materials back to a sorting and crushing facility.
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The Increasing Need for Top Quality Recycled Aggregate
Before commencing the crushing procedure, it must be determined what the end product is to be used for to make sure that the recycled aggregate is to satisfy the required standards. There’s huge demand for recycled concrete aggregate to be used back in the construction process. As a product, recycled concrete aggregate can be utilised for nearly every type of concrete structural work, road surfacing or pipe laying project. Having passed through the crusher the chunks of aggregate will be separated by size. Bigger pieces may be retained as a decorative product for use in landscaping rockery projects, or they could be passed back through the crusher to be pummeled to a smaller size. The small bits of recycled aggregate may be suitable for use as a gravel on new construction projects, road laying or driveways at home. The crushing units are now capable of achieving top quality small aggregate grades such as the production of a 20-5mm gravel which can be bagged and used in the garden at home or bought in bulk as part of projects involving new concrete production. The advances in technology mean that the recycling of aggregates for other uses such as a simple gravel product or for use in concrete products has greatly reduced the need to dig quarries to mine for gravel. Recycled aggregates have become a versatile reusable product and has eliminated the need for large volumes of a good material to be disposed of in landfill and therefore offer significant environmental benefits.
The demand for good quality crushed aggregate is increasing. There’s key standards in place which are focused upon improving the recycled concrete aggregate industry. By means of research and development, more widespread applications are now being discovered for the use of recycled aggregate. No more is concrete, just concrete. What we are talking about now a variety of different grades of recycled aggregate, ranging from the large chunks of aggregate to very precise 6f2 recycled concrete which can be employed as a sub-base material for construction jobs, or 20-5mm recycled aggregate, which is a gravel and can be used in road construction or at home on driveways. In addition to being used as a mix for road construction, recycled aggregate is being used as bedding for pipe laying or base material prior to construction projects starting. In achieving such top quality grades the 20-5mm recycled aggregate can be used as an aggregate base in highway building and the quality meets the standards necessary to allow its reuse in concrete production.
On the list of important requirements when you use recycled aggregate is choosing the best specification for your task. By way of example, when making use of 20-5mm coarse graded aggregate as a road foundation, the depth of the layer demanded will have to be determined to tolerate traffic flows. Traffic flow on a motorway will be significantly different to that of a country road. One reason aggregate produced to a 20-5mm specification is commonly employed as a road base is that it supports good drainage. Once the recycled aggregate is laid, appropriate layers of asphalt or concrete can be laid above it to construct the road surface.
In recent years, in the United Kingdom we seem to have more rain than hot sunshine and for that reason the chosen aggregate must be able to tolerate variances in temperatures and conditions e.g. dampness for long periods, torrential downpours, long dry spells. With its good drainage qualities, the recycled 20-5mm product may be the ideal choice for a lot of sand and gravel applications including, pipe bedding, driveways and footpaths, landscaping, plus for use in ready mixed and precast concrete products.
The build programme for London’s Olympic Village, has specified the use of a clean recycled concrete aggregate crushed to a 20-5mm specification.
Recycled Aggregates and the 2012 Olympics
In its bid for the 2012 Olympic Games, London placed sustainability as the focus of its bid. The bid team recognized a major opportunity to boost awareness of climate change and the concerns that surround it, and bring it to the Globe’s attention. With the eyes of the Entire world observing, the Olympic Games present a unique chance to convey important points with regards to sustainability. Through the whole growth and development of the Olympics project, there’s a responsibility to make 2012 the most sustainable Olympics ever held. This focus originated when planning the design and build programmes for the amenities and venues, the transportation links and system, the hosting of the Games themselves and will end by leaving behind a long lasting legacy of a sustainable healthy environment.
Since London was awarded the Games, all partners involved in the development specifications, from the building of the Olympic Arena, the Olympic Village and transportation links between the venues have been encouraged upon ensuring the use wherever possible of sustainable resources. Across the entire Olympic build programme construction managers have worked hard to discover practical sustainable materials for use in the build programme. At the end of the overall project we will see some clearly visible cases of the use of sustainable products.
Equally there will be many more that are much less visible, and furthermore, many which will be not visible at all. One of those products which visitors to the games and its many locations won’t even consider how recycled aggregates are already used as part of the overall construction project. However developers and specifiers of resources for use in the build programme will be secure in the knowledge that they have selected sustainable products which include, the most appropriate recycled concrete aggregates as part of the project. With its identified characteristics, let us hope that somewhere in the global Television coverage the 20-5mm recycled aggregate gets a reference somewhere, somehow.
Conclusion
How times have developed recently in the demolition and construction industry. Businesses have had to adjust to meet tough green requirements. As with almost any segment, new regulations and legislation determine the criteria to which your company must aspire, if it is to achieve success.
Companies engaged in the manufacturing of recycled concrete aggregate aren’t any different. These are generally categorised as processed materials and must conform to a particular product specification which can be used in the construction process. The standard BS8500-2 offers a full specification for the uses of recycled concrete aggregates in concrete, although with such a vast range of recycled aggregates an all encompassing specification for the use of these aggregates is yet to be determined. The main thing is that the industry does not stand still and wait for the specifications to be finalised. The versatility of recycled aggregates means that demolition contractors operating crushing plants are seeking to identify markets through which to sell their recycled products. The advances in crusher technology and machinery has seen a big increase in the options now available in providing large chunks of recycled aggregate for landscape gardening use in rockeries, down to a gravel type 20-5mm recycled aggregate with its good drainage qualities for use in road construction and driveways. The demolition and construction industry now places sustainability at the forefront of its future development projects.
Tomorrow
