Introduction
Mention the term demolition to almost anyone and the image that immediately comes up is a vision of a building being blown up and collapsing to the ground. A lot of people have stated they would really like to push the button, to trigger the explosive systems which will bring a disused building to the floor. In many cases what comes down, must go up and we are seeing many old buildings being razed making way for potential future development, often together with a regeneration project.
For companies who over several years have created their business surrounding the demolition of structures, the demolition sector is now far more reaching than simply blowing up old and unwanted buildings. As soon as the structure is demolished the huge task of site clearance will begin and in a modern world where consideration of the environmental impacts are very high on a good number of peoples agenda, the material residues from demolition ought to be separated for recycling applications. This can include such products as steel, wood, plastic, brickwork and concrete.
The majority of the materials tend to be bulked up and transported to appropriate recycling plants for reprocessing. Materials such as bricks and concrete are generally crushed and turned into a recycled concrete aggregate substance completely ready for reuse in the making of new roadways or buildings. Ever more though, via breakthroughs in technological development, derivatives such as rubble to be recycled must meet a very high specification for reuse in construction projects.
When crushed, the different sizes of recycled aggregate will determine the future usage potential of the product. Larger sizes could possibly be used as decorative rockery products in gardening whilst much finer, almost shingle like product may be used to provide a bedding for pipe laying or for a layer in street construction. Through an growing amount of possibilities identified for the reuse of recycled aggregate, the entire demolition and construction industry is generating 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 imposed a duty on all waste items going to landfill. The duty is paid in addition to regular gate fees for waste being disposed in landfill and since its introduction the price has risen annually. When first introduced, the typical rate of duty for general waste materials going to landfill was �7 per tonne and �2 per tonne for inert products. The tax should encourage commercial and industrial companies and local authorities collecting from households, to divert waste away from landfill for recycling. In April 2009, the standard rate of landfill tax rose to �40 per tonne and is timetabled to rise each year by �8 per tonne until 2013. The lower level of tax incurred upon any inert materials going to landfill including concrete and soils, has stayed comparatively stable recently and is currently at �2.50 per tonne.
However, the weight of a bulk load of inert materials going straight to landfill will ensure that the whole cost of disposal becomes extremely expensive and so even in the demolition and construction sector, diverting waste from landfill is a priority. The arrival of landfill tax has been a key driver in encouraging greater diversion of inert materials from landfill, to be used in sustainable development projects.
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Next time you see a demolition project happening or pass any construction site during a build programme, it’s clear to see the volume of waste materials being created. If waste material isn’t in skips, heaps of rubble will be stacked high. The placing of construction waste in skips has been a major problem for waste contractors for quite some time. I have worked within the waste industry, I have seen skip lorries tipped backwards with the cab of the vehicle up in the air, because of the sheer overloading of waste skips with construction site waste.
Every year, the uk produces around 330 million tonnes of waste material and approximately 90 million tonnes of this is coming from building and demolition wastes. This number has stayed reasonably constant since 2001. Approximately two thirds of this waste is normally recycled or reused in land reclamation or agricultural development projects. Since the later part of the 1990s there has been a steady rise in the volumes of construction waste material being recycled and this has been aided by advances in technology which have resulted in improved crushing products to make more widespread use of varying specifications of recycled aggregates. There’s been a genuine focus upon the United Kingdom construction community to encourage more recycling of waste materials on site.
In recent years, the construction sector as a whole has worked hard to encourage construction project managers to place a larger focus upon recycling on site. This has resulted in a growth in the recycling of inert materials from site.
Prior to the introduction of the landfill duty almost all construction site waste including bricks and concrete would be bulked up and taken to a landfill site for disposal. No deliberation was given to recycling. These day there are stringent regulations across the sector, coupled with an increase in environmental focus, as well as the commercial rewards in making certain that this kind of waste is recycled. There is also better recognition of the wide array of opportunities to use recycled aggregates in the construction process on alternative construction projects or in fields such as landscaping or home and garden Do-it-yourself. Following the demolition process, together the waste concrete, bricks, masonry etc will probably be transformed into a recycled concrete aggregate.
To recycle concrete aggregate to a high standard and resalable product, it must be entirely free of other debris such as wood, paper, card, steel and other general waste materials. The final product also needs to conform to the specifications of British Standard BS 8500. The process of recycling the concrete can usually be achieved in one of two ways. Some demolition companies will transport a crushing device on the demolition site, whereas some contractors will opt to carry the waste to be recycled, to their premises for separation for recycling or re-use. On projects where demolition and new construction is to occur at the same site, the contractor is likely to locate a crushing unit on site to escape incurring additional transportation costs in taking the material back to a sorting and crushing centre. There is now very sophisticated crushing equipment existing to reduce concrete to a very fine specification.
Larger buildings being demolished, will require skilled asbestos removal and demolition contractors need to be appointed to manage the task.
The Growing Interest in High Quality Recycled Aggregate
Before commencing the crushing procedure, it has to be determined what the end product is to be used for to ensure that the recycled aggregate is to meet the necessary standards. There is huge demand for recycled aggregate to be used back in the construction process. As a product, recycled aggregate can be used for just about any type of concrete structural function, road surfacing or pipe laying project. Having passed through the crusher the chunks of aggregate will be sorted by size. Bigger pieces may be retained as a cosmetic product to be used in landscaping rockery projects, or they might be passed back through the crusher to be crushed to a smaller size. The small pieces of recycled aggregate could be suitable for use as a gravel on new construction projects, road laying or driveways at home. The crushing machines are now capable of achieving high 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 purchased 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 high quality crushed aggregate is increasing. There’s key standards in place that are focused upon improving the recycled aggregate market. Through research and development, more widespread applications are being identified for the employment of recycled aggregate. No longer is concrete, just concrete. What we are talking about now a wide range of distinct grades of recycled aggregate, which range 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 utilised in road construction or at home on driveways. As well as being employed as a mix for road construction, recycled aggregate is being used as bedding for pipe laying or foundation material prior to construction projects starting. In achieving such top quality grades the 20-5mm recycled aggregate can be utilised as an aggregate base in highway construction and the quality meets the standards necessary to allow its reuse in concrete production.
One of the important requirements when you use recycled aggregate is selecting the best specification for the task. By way of example, when making use of 20-5mm coarse graded aggregate as a road base, the thickness of the layer required must be determined to withstand traffic flows. Traffic flow on a motorway will be significantly different to that of a country road. One good 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 installed, appropriate layers of asphalt or concrete can be laid above it to form the road surface.
Recently, in the United Kingdom we seem to have more rain than sunshine and therefore the chosen aggregate must have the ability 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 could be the appropriate choice for some sand and gravel applications including, pipe bedding, driveways and footpaths, landscaping, plus for use in ready mixed and precast concrete products.
Following demolition, contractors will use crushing machinery to produce recycled concrete aggregates from the waste bricks and concrete for use in future construction processes.
Recycled Aggregates and the 2012 Olympics
In its bid for the 2012 Olympic Games, London placed sustainability as the focal point of its bid. The bid team identified a major opportunity to raise awareness of climate change and the concerns that surround it, and bring it to the Globe’s attention. With the eyes of the World watching, the Olympic Games present an exceptional opportunity to communicate important messages with regards to sustainability. Through the whole growth and development of the Olympic project, there is a commitment to make 2012 the most sustainable Olympics ever held. This focus originated when preparing the design and build programmes for the amenities and venues, the transport links and system, the hosting of the Games themselves and will conclude by leaving behind a long lasting legacy of a sustainable natural environment.
Ever since London was granted the Games, all companies involved with the development specifications, from the design of the Olympic Arena, the Olympic Village and transport links to the venues have been encouraged upon ensuring the use wherever possible of sustainable materials. Across the entire Olympic build programme construction managers have worked hard to identify acceptable sustainable materials for use in the build programme. By the end of the whole project we will see some clearly obvious examples 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. Some of those products which visitors to the games and its countless locations won’t even think about how recycled aggregates are used as part of the overall construction project. But developers and specifiers of materials to be used in the build programme will be comfortable in the knowledge that they have selected sustainable products which include, the most appropriate recycled concrete aggregates as part of the project. With its recognized qualities, let’s hope that somewhere in the worldwide Television coverage the 20-5mm recycled aggregate gets a reference somewhere, somehow. Imagine being asked to supply recycled aggregate which meets a very specific 20-5mm clean material specification, to help build the 2012 Olympic Village.
Conclusion
How times have developed in recent years for the demolition and construction marketplace. Organisations have needed to adjust to meet tough environmental conditions. As with nearly every sector, new regulations and legislation dictate the criteria to which your business must aspire, if it is to achieve success.
Companies engaged in the manufacturing of recycled aggregate are not 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 most important 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 to be used in road construction and driveways.
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