Introduction
Mention the phrase demolition to almost any person and the picture that instantly comes up is usually a vision of a structure being blown up and collapsing to the ground. Many people have said that they would love to push the button, to detonate the explosive devices which will bring a disused property to the floor. Often the thing that comes down, must go up so we are seeing many unsightly buildings being razed to help with making way for future development, normally as part of a regeneration project.
For organizations who over a number of have developed their business within the demolition of properties, the demolition arena is now much more reaching than simply demolishing outdated buildings. Once the structure is demolished the huge task of site clearance will begin and in a modern world where consideration of the environmental impacts are high on many peoples agenda, the material residues coming from demolition should be sorted for recycling applications. This will likely include such materials as steel, wood, plastic, brickwork and concrete.
The vast majority of the materials are bulked up and shipped to the appropriate recycling plants for reprocessing. Materials such as bricks and concrete can be crushed and become a recycled concrete aggregate product completely ready for reuse in the making of new highways or buildings. Ever more though, by means of advancements in technological development, residues like rubble to be recycled have to meet a very high specification for reuse in construction projects.
When crushed, the various grades of recycled aggregate will govern the future usage potential of the product. Large sizes could possibly be employed as ornamental rockery products in gardening while much finer, almost shingle like product may be used to provide a bedding for pipe laying or for a layer in street construction. With an growing variety of options identified for the reuse of recycled aggregate, the whole demolition and construction industry is generating a substantial contribution to sustainable development.
Reasons Behind the Increased Focus on Recycling from Construction and Demolition Projects
In 1996, UK Government added a duty on all wastes going to landfill. The tax is paid out on top of normal gate rates for waste being disposed in landfill and since its initial release the fee has increased on an annual basis. When it was first introduced, the standard level of duty for general waste products being sent to landfill was �7 per tonne and �2 per tonne for inert products. The tax should inspire commercial and industrial firms and local authorities collecting from households, to divert waste away from landfill for recycling. In April ’09, the standard level of landfill duty rose to �40 per tonne and it is scheduled to increase each year by �8 per tonne until 2013. The lower rate of duty charged upon any inert materials going to landfill including concrete and soils, has remained reasonably stable in recent years and is presently at �2.50 per tonne.
However, the weight of a bulk load of those inert materials going straight to landfill will ensure that the full cost of disposal becomes horrendously expensive and so even in the demolition and construction industry, diverting waste from landfill is a top priority.
A number of demolition contractors will offer discount crushed stone simply to move it off their premises.
Next time you see a demolition project happening or pass almost any construction site during a build programme, it’s very clear to see the quantity of waste materials being produced. If waste is not in skips, heaps of rubble will be stacked high. The placing of concrete waste material in skips has been a significant problem for waste companies for several years. I have worked in the waste sector, 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.
Each and every year, the uk produces close to 330 million tonnes of waste materials and approximately 90 million tonnes of this is coming from construction and demolition wastes. This figure has stayed fairly steady since 2001. Approximately two thirds of this waste is normally recycled or reused in land reclamation or agricultural improvement projects. Since the late 1990s there has been a steady increase in the quantities of construction waste material being recycled and this has been helped by improvements in technology which have resulted in improved crushing products to create more common use of different grades of recycled aggregates.
In the past few years, the construction industry in general has worked hard to persuade construction site supervisors to put a larger focus upon recycling on site. This has resulted in an increase in the recycling of inert materials from site.
Prior to the introduction of the landfill levy almost all construction site waste including bricks and concrete would be bulked up and transported to a landfill site for disposal. No particular attention was given to recycling. Nowadays there are stringent restrictions across the sector, coupled with an increase in environmental consciousness, and also the commercial benefits in making sure that this type of waste is recycled. There is also increased recognition of the vast array of opportunities to re-use recycled aggregates in the construction process on alternative construction projects or in environments such as landscaping or home and garden DIY. Following the demolition process, together the waste concrete, bricks, masonry etc will probably 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 grade and resalable product, it needs to be totally free from other impurities such as wood, paper, card, steel and other general waste materials. The final product also needs to 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 contractors will locate a crushing device on the demolition site, whereas various contractors will choose to carry the waste to be recycled, 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 place a crushing appliance on site to escape incurring additional transport costs in taking the material back to a sorting and crushing centre.
Approval from the local authority is going to be required prior to site clearance contractors commencing the task of demolishing a building.
The Growing Demand for Top Quality Recycled Aggregate
Before commencing the crushing procedure, it needs to be determined what the end product will be used for to make sure the recycled aggregate is to match the required standards. There’s huge demand for recycled concrete aggregate to be used within the construction process. As a product, recycled concrete aggregate can be utilised for almost any type of concrete structural function, road surfacing or pipe laying project. Having passed through the crusher the pieces of aggregate can be sorted by size. Bigger pieces may be retained as a cosmetic product for use in landscaping rockery projects, or they may be passed back through the crusher to be pummeled to a reduced size. The smaller 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 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 need for high quality crushed aggregate is ever-increasing. There are key standards in position that are focused upon improving the recycled aggregate market. Through research and improvement, more widespread uses are being discovered for the use of recycled aggregate. No more is concrete, just concrete. What we are talking about now a variety of distinct grades of recycled aggregate, ranging from the large chunks of aggregate to very specific 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 used in road construction or at home on driveways. As well as being used as a mix for road construction, recycled aggregate is being used as bedding for pipe laying or footing material prior to construction projects commencing. In achieving such good quality grades the 20-5mm recycled aggregate can be used as an aggregate base in road building and the quality meets the standards necessary to allow its reuse in concrete production.
On the list of important considerations when using recycled aggregate is selecting the best specification for the task. For example, when making use of 20-5mm coarse graded aggregate for a road foundation, the depth of the layer required must be determined to stand up to 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 helps good waterflow and drainage. Once the recycled aggregate is installed, suitable layers of asphalt or concrete can be laid over it to build the road surface.
Recently, in the United Kingdom we appear to have more bad weather than sunshine and for that reason the selected aggregate must be able to tolerate variances in temperatures and conditions e.g. dampness for very long periods, torrential downpours, long dry spells. With its good drainage qualities, the recycled 20-5mm product is the perfect choice for many sand and gravel applications including, pipe bedding, driveways and footpaths, landscaping, and also for use in ready mixed and precast concrete products. With its drainage qualities, 20-5mm recycled aggregate is a versatile product.
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Recycled Aggregates and the 2012 Olympic games
In its bid for the 2012 Olympic Games, London set sustainability as the focal point of its bid. The bid team recognized a big opportunity to increase awareness of climate change and the concerns that encircle it, and bring it to the World’s notice. With the eyes of the Entire world watching, the Olympics provide a unique opportunity to communicate important messages concerning sustainability. Throughout the whole development of the Olympics project, there’s a responsibility to make 2012 the most sustainable Olympics ever held. This focus began when setting up the design and build programmes for the facilities and venues, the transportation links and system, the hosting of the Games themselves and will conclude by leaving a long lasting heritage of a sustainable natural environment.
Since London was awarded the Games, all suppliers involved in the development requirements, from the construction of the Olympic Stadium, the Olympic Village and transportation links between the venues have been focused upon ensuring the use wherever possible of sustainable materials. Throughout the entire Olympic build programme construction managers have worked hard to discover suitable sustainable materials for use in the build programme. At the end of the whole project there will be some clearly obvious cases of the use of sustainable products.
At the same time 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 sites will not even consider how recycled aggregates are already specified 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 aggregates as part of the project. With its identified characteristics, let us hope that somewhere in the world wide 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 recently for the demolition and construction market. Businesses have been required to adapt to meet tough green conditions. As with just about any segment, new regulations and legislation dictate the standards to which your company must aspire, if it is to be successful.
Companies involved in the manufacturing of recycled aggregate are not any different. These are 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 to be used in road construction and driveways.