Introduction
Mention the word demolition to almost any person and the scene that instantly comes to mind is a vision of a structure being blown up and collapsing to the floor. Plenty of people have claimed that they would love to press the button, to trigger the explosive units which will bring a disused property to the ground. On many occasions the thing that comes down, must go up and we are seeing many unsightly properties being taken down to make way for potential future development, usually as part of a regeneration project.
For firms that over a number of have created their business surrounding the demolition of properties, the demolition market is now considerably more reaching than just demolishing unwanted buildings. Once the property is demolished the huge task of site clearance begins and in a community where consideration of the environmental effects are ever increasing on most peoples agenda, the material residues provided by demolition have to be sorted for recycling purposes. This will include such products as steel, wood, plastic, brickwork and concrete.
The majority of the materials are bulked up and transported into the appropriate recycling plants for reprocessing. Materials such as bricks and concrete can be crushed and turned into a recycled concrete aggregate substance available for reuse in the making of new highways or structures. Increasingly though, through breakthroughs in technological development, residues including rubble to be recycled must meet an extremely high standard for reuse in construction projects.
When crushed, the different sizes 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 as a bedding for pipe laying or for a layer in road construction. Through an increasing amount of possibilities recognized for the reuse of recycled aggregate, the entire demolition and construction industry is building a substantial contribution to sustainable development.
Reasons For the Increased Focus on Recycling from Construction and Demolition Projects
In 1996, UK Government imposed a duty on all wastes going to landfill. The levy is paid on top of normal gate rates for waste materials being disposed in landfill and since its initial release the price has risen on an annual basis. When it was first introduced, the standard rate of duty for general waste materials being sent to landfill was �7 per tonne and �2 per tonne for inert substances. The levy should encourage commercial and industrial organisations and local authorities collecting from properties, to divert waste away from landfill for recycling. In April ‘09, the typical rate of landfill tax increased to �40 per tonne and it is scheduled to rise every 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 stable in recent years and is currently at �2.50 per tonne.
Nonetheless, the weight factor alone of a bulk load of those 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 arena, diverting waste from landfill is a priority.
The materials which remain after making use of demolition equipment may be converted into a variety of reusable products for use in other construction projects.
Next time you see a demolition project in progress or go past any construction site during a build programme, it is obvious to see the volume of waste material being created. If waste is not in skips, heaps of rubble will be stacked high. The placing of construction waste materials in skips has been a major issue for waste contractors for quite some time. Having worked within the waste sector, I’ve seen skip lorries tipped backwards with the cab of the vehicle up in the air, because of the sheer overloading of waste skips with building site waste.
Each and every year, the united kingdom generates close to 330 million tonnes of waste and approximately 90 million tonnes of this is coming from building and demolition wastes. This number has stayed reasonably steady since 2001. Approximately two thirds of this waste is usually recycled or reused in land reclamation or agricultural development projects. Since the later part of the 1990s there has been a gradual rise in the volumes of construction waste material being recycled and this has been aided by improvements in technology which have led to improved crushing products to create more widespread use of various grades of recycled aggregates. There’s been a genuine focus upon the UK construction sector to encourage more recycling of waste on site.
In the past few years, the construction sector in general has worked hard to persuade construction site managers to put a larger emphasis upon recycling on site. This has led to a growth in the recycling of inert materials from site.
Before the introduction of the landfill duty almost all construction site waste including bricks and concrete was bulked up and taken to a landfill site for disposal. No particular attention was given to recycling. There are now stringent regulations across the sector, coupled with an increase in environmental consciousness, as well as the commercial advantages in making sure that this kind of waste is recycled. Addititionally there is greater recognition of the wide array of 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 probably 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 debris such as wood, paper, card, steel and other general waste materials. The final product must comply with the specifications of British Standard BS 8500. The process of recycling the concrete can normally be achieved in one of two ways. Some demolition contractors will install a crushing machine on the demolition site, whereas a lot of contractors will choose to move the waste to be recycled, to their premises for segregation 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 place a crushing machine on site to avoid incurring extra transport costs in taking the material to a sorting and crushing centre. There is now very advanced crushing equipment available to reduce concrete to a very fine specification.
Most demolition contractors work hard to recycle the maximum amount of waste as possible from the demolished building.
The Increasing Interest in High Quality Recycled Aggregate
Before starting the crushing process, it must be determined what the end product is to be used for to make sure that the recycled aggregate is to match the necessary standards. There’s huge requirement for recycled aggregate to be used during the construction process. As a product, recycled concrete aggregate can be used for virtually any form of concrete structural work, road surfacing or pipe laying project. Having passed through the crusher the chunks of aggregate will be sorted by size. Bigger pieces can be retained as a cosmetic product to be used in landscaping rockery projects, or they may be passed back through the crusher to be crushed to a smaller size. The smaller pieces of recycled aggregate may 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.
The demand for high quality crushed aggregate is increasing. There’s key standards in place that are concentrated upon improving the recycled concrete aggregate market. Through research and improvement, more widespread applications are now being identified for the employment of recycled aggregate. No longer is concrete, just concrete. What we are talking about now a variety of distinct grades of recycled aggregate, which range from the large sections 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 used as a mix for highway construction, recycled aggregate is being used as bedding for pipe laying or footing 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 building and the quality meets the standards required to allow its reuse in concrete production. The 20-5mm recycled aggregate is a very versatile product.
One of several important requirements when using recycled aggregate is selecting the right specification for the task. For instance, when using 20-5mm coarse graded aggregate for a road base, the thickness of the layer needed must be determined to stand up to 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 used 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 over it to create the road surface.
In recent years, in the United Kingdom we appear to have more rain than hot sunshine and therefore the chosen aggregate must be able to endure variances in temperatures and conditions e.g. dampness for very long periods, torrential downpours, long dry spells. With its good waterflow and drainage characteristics, the recycled 20-5mm product may be the perfect choice for some sand and gravel applications including, pipe bedding, driveways and footpaths, landscaping, plus for use in ready mixed and precast concrete products.
Before demolition can commence a full site survey must be undertaken to establish if specialist asbestos removal is required as part of the project.
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 problems which encircle it, and bring it to the Globe’s notice. With the eyes of the Entire world observing, the Olympic Games present an exceptional opportunity to communicate key points regarding sustainability. Through the entire development of the Olympic project, there is a responsibility to make 2012 by far the most sustainable Olympics ever held. This focus originated when setting up the development and build programmes for the facilities and venues, the transport links and network, the hosting of the Games themselves and will conclude by leaving a long lasting heritage of a sustainable healthy environment.
Since London was granted the Games, all companies associated with the development requirements, from the construction of the Olympic Stadium, the Olympic Village and transportation links between the venues have been focused upon guaranteeing the use wherever possible of sustainable resources. Throughout the entire Olympic build programme developers have worked hard to locate practical sustainable materials for use in the build programme. At the end of the whole project we will see some clearly obvious 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. Some of those products which visitors to the games and its countless venues will not even think about how recycled aggregates are already employed as part of the overall construction project. However developers and specifiers of materials to be used within the build programme will be secure in the knowledge that they have selected sustainable products including, the most appropriate recycled concrete aggregates as part of the project. With its identified qualities, let us hope that somewhere in the worldwide TV 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 changed recently in the demolition and construction market. Businesses have had to adjust to meet demanding environmental specifications. As with virtually any sector, new regulations and legislation dictate the benchmarks to which your business must aspire, if it is to be successful.
Companies involved in the manufacturing of recycled concrete aggregate aren’t any different. These are classed 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 offering 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 highway construction and driveways.
