Introduction
Mention the term demolition to almost anyone and the scene that immediately comes up is a vision of a building being blown up and collapsing to the floor. Plenty of people have claimed that they would love to press the button, to detonate the explosive systems which bring a disused building to the ground. Often what comes down, must go up and now we are seeing many old buildings being demolished to help with making way for potential future development, usually during a regeneration project.
For businesses that over a number of have established their business surrounding the demolition of structures, the demolition sector has become considerably more reaching than just blowing up old buildings. When the building is demolished the tremendous task of site clearance will begin and in a world where consideration of the environmental impacts are high on a good number of peoples agenda, the material remains provided by demolition need to be sorted for recycling purposes. This will likely include such materials as steel, wood, plastic, brickwork and concrete.
Almost all of the materials are bulked up and shipped into the appropriate recycling plants for reprocessing. Resources such as bricks and concrete are generally crushed and converted into a recycled concrete aggregate product completely ready for reuse in the construction of new roads or structures. Increasingly though, by means of advancements in technological development, derivatives such as rubble to be recycled must meet a very high specification for reuse in construction projects.
When crushed, the assorted sizes of recycled aggregate will govern the likely usage potential of the product. Large sizes might be used as decorative rockery products in gardening while much finer, shingle like product can be used to provide a bedding for pipe laying or as a layer in highway construction. Through an increasing amount of possibilities identified for the reuse of recycled aggregate, the whole demolition and construction industry is generating a significant 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 Focus on Recycling from Construction and Demolition Projects
In 1996, UK Government added a levy on all waste items 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 price has risen on an annual basis. When first introduced, the common rate of duty for general waste materials being sent to landfill was �7 per tonne and �2 per tonne for inert products. The tax is designed to motivate commercial and industrial organisations and local authorities collecting from households, to divert waste away from landfill for recycling. In April ’09, the typical rate of landfill duty rose to �40 per tonne and it is scheduled to increase each year by �8 per tonne until 2013. The reduced level of tax charged upon any inert materials going to landfill including concrete and soils, has remained fairly stable in recent years and is presently at �2.50 per tonne.
Nonetheless, the weight of a bulk load of these inert products going directly to landfill will guarantee that the entire cost of disposal becomes extremely expensive and so even in the demolition and construction industry, diverting waste from landfill is a top priority.
Having completed the initial step, demolition companies frequently bring crushing machinery on site to crush the brickwork and concrete remains.
Next time you see a demolition project happening or go past any construction site during a build programme, it will be very clear to see the amount of waste material being generated. If waste material is not in skips, piles of rubble will probably be stacked high. The placing of concrete waste in skips has been a major issue for waste companies for many years. I have worked within the waste industry, I’ve seen skip lorries tipped backwards with the cab of the vehicle up in the air, due to the sheer overloading of waste skips with building site waste.
Each and every year, the uk produces around 330 million tonnes of waste and it is estimated that around 90 million tonnes of this is coming from construction and demolition wastes. This figure has stayed relatively constant since 2001. About two thirds of this waste is usually recycled or reused in land reclamation or agricultural improvement projects. Ever since the later part of the 1990s there has been a steady increase in the quantities of construction waste being recycled and this has been assisted by improvements in technology that have resulted in improved crushing solutions to create more widespread use of different grades of recycled aggregates.
In recent years, the construction industry in general has worked hard to encourage construction project supervisors to put a larger focus upon recycling on site. This has led to a rise in the recycling of all inert materials from site.
Before the introduction of the landfill tax just about all construction site waste including bricks and concrete would be bulked up and taken to a landfill site for disposal. No regard was given to recycling. There are now strict limitations across the sector, in conjunction with an increase in environmental consciousness, as well as the commercial benefits in ensuring that this sort of waste is recycled. Addititionally there is significantly greater recognition of the large choice of potential business opportunities to use recycled aggregates in the construction process on future 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 likely 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 needs to be completely free from other debris such as wood, paper, card, steel and other general waste materials. The final product must comply with the requirements of British Standard BS 8500. The task of recycling the concrete can usually be achieved in one of two ways. Some demolition contractors will install a crushing device on the demolition site, whereas some contractors will prefer to carry the waste to be recycled, back to their premises for segregation for recycling or re-use. On projects where demolition and new construction is to occur at the same location, the contractor is likely to locate a crushing appliance on site to avoid incurring additional transport costs in taking the materials to a sorting and crushing centre.
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The Increasing Need for Top Quality Recycled Aggregate
Before commencing the crushing procedure, it has to be determined what the end product will be used for to ensure that the recycled aggregate is to meet the required standards. There is huge requirement for recycled aggregate to be used during the construction process. As a product, recycled aggregate can be used for virtually any kind of concrete structural work, road surfacing or pipe laying project. Having passed through the crusher the pieces of aggregate will be sorted by size. Bigger pieces can be retained as a cosmetic product for use in landscaping rockery projects, or they could be passed back through the crusher to be crushed to a reduced size. The smaller sized bits of recycled aggregate might be suited to 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 need for high quality crushed aggregate is growing. There’s key standards in place which are concentrated upon improving the recycled concrete aggregate industry. Through research and improvement, more widespread applications are being discovered for the use of recycled aggregate. No more is concrete, just concrete. What we are talking about now are many different grades of recycled aggregate, ranging from the large sections of aggregate to very precise 6f2 recycled concrete which can be used 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. In addition to being employed as a mix for highway construction, recycled aggregate is being used as bedding for pipe laying or foundation material prior to construction projects starting. In achieving such good quality grades the 20-5mm recycled aggregate can be used as an aggregate base in road construction and the quality meets the specifications required to allow its reuse in concrete production.
One of several 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 foundation, the depth of the layer required must be determined to withstand traffic flows. Traffic flow on a motorway is going to 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 waterflow and drainage. Once the recycled aggregate is installed, appropriate layers of asphalt or concrete can be laid across it to construct the road surface.
Recently, in the United Kingdom we appear to have more bad weather than hot sunshine and therefore the selected aggregate must have the ability to withstand variances in temperature and conditions e.g. dampness for long periods, torrential downpours, long dry spells. With its good drainage characteristics, the recycled 20-5mm product may be the appropriate choice for some sand and gravel applications including, pipe bedding, driveways and footpaths, landscaping, and also for use in ready mixed and precast concrete products.
Where sustainability is a key focus of a construction project, the use of specified recycled concrete products offers a sustainable concrete solution.
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 big opportunity to boost awareness of climate change and the issues which encircle it, and bring it to the World’s attention. With the eyes of the World observing, the Olympic Games present a unique opportunity to communicate important messages regarding sustainability. Through the entire development of the Olympics project, there exists a commitment to make 2012 the most sustainable Olympic Games ever held. This focus began when preparing the development and build programmes for the facilities and venues, the transportation links and network, the hosting of the Games themselves and will end by leaving behind a long lasting heritage of a sustainable healthy environment.
Since London was awarded the Games, all companies involved with the development requirements, from the construction of the Olympic Stadium, the Olympic Village and transportation links between the venues have been encouraged upon ensuring the use wherever possible of sustainable materials. Across the entire Olympic build programme developers have worked hard to identify appropriate sustainable materials for use in the build programme. At the conclusion of the overall project there will be some clearly visible examples of the use of sustainable products.
Similarly 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 numerous locations won’t even consider how recycled aggregates have been used as part of the overall construction project. But developers and specifiers of materials to be used in the build programme will be secure in the knowledge that they have selected sustainable products including, the most suitable recycled concrete aggregates as part of the project. With its recognized characteristics, let’s hope that somewhere in the world wide TV coverage the 20-5mm recycled aggregate gets a mention 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 changed in recent years in the demolition and construction market. Businesses have had to adapt to meet demanding environmental requirements. As with just about any market, new laws and legislation determine the benchmarks to which your company must aspire, if it is to achieve success.
Companies involved in the generation of recycled 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 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 supplying 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.