Introduction
Mention the term demolition to just about anyone and the scene that immediately comes to mind is usually a vision of a structure being blown up and collapsing to the floor. Lots of people have stated they would love to press the button, to detonate the explosive systems which will bring a disused building to the floor. Often the thing that comes down, must go up and we are seeing many old buildings being taken down to help with making way for potential future development, usually during a regeneration project.
For firms that over many years have created their business surrounding the demolition of buildings, the demolition arena has become much more reaching than simply blowing up outdated buildings. When the building is demolished the huge task of site clearance starts and in a community where consideration of the environmental impacts are ever increasing on most peoples agenda, the material remains provided by demolition have to be separated for recycling purposes. This will likely include such products as steel, wood, plastic, brickwork and concrete.
The majority of the materials are bulked up and transported to the appropriate recycling plants for reprocessing. Products such as bricks and concrete are usually crushed and converted into a recycled concrete aggregate product completely ready for reuse in the construction of new highways or structures. Ever more though, by means of breakthroughs in technological development, derivatives such as rubble to be recycled have to meet a high standard for reuse in construction projects.
When crushed, the varied sizes of recycled aggregate will govern the likely usage potential of the product. Larger sizes could possibly be utilised as decorative rockery products in landscaping while much finer, almost shingle like product can be utilised to provide a bedding for pipe laying or as a layer in road construction. With an increasing amount of opportunities identified for the reuse of recycled aggregate, the whole 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 For the Increased Concentration on Recycling from Construction and Demolition Projects
In 1996, UK Government added a duty on all wastes going to landfill. The duty is paid out in addition to normal gate fees for waste material being disposed in landfill and since its introduction the cost has risen annually. When it was first introduced, the common rate of tax for general waste products being sent to landfill was �7 per tonne and �2 per tonne for inert materials. The tax should encourage commercial and industrial businesses and local authorities collecting from households, to divert waste away from landfill for recycling. In April ‘09, the standard level of landfill duty grew to �40 per tonne and it is scheduled to rise every year by �8 per tonne until 2013. The lower level of tax incurred upon any inert materials going to landfill like concrete and soils, has stayed reasonably steady in recent years and is presently at �2.50 per tonne.
Nonetheless, the weight of a bulk load of those inert products going direct to landfill will guarantee 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.
Advancements in crushing machinery technology now enables recycled crushed stone production from 20-5mm which is ideal for many different uses on account of its excellent drainage qualities.
Next time you see a demolition project in progress or go past any construction site during a build programme, it’s very clear to see the quantity of waste materials being generated. If waste material is not in skips, heaps of rubble will be stacked high. The placing of concrete waste material in skips has been a serious problem for waste contractors for many years. I have 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 construction 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 construction and demolition wastes. This figure has stayed reasonably steady since 2001. Close to two thirds of this waste is normally recycled or reused in land reclamation or agricultural improvement projects. Ever since the late 1990s there’s been a steady increase in the volumes of construction waste material being recycled and this has been helped by improvements in technology that have led to improved crushing products to make more frequent use of various grades of recycled aggregates. There is a real focus upon the United Kingdom construction sector to encourage increased recycling of waste materials on site.
In recent years, the construction sector as a whole has worked hard to persuade construction site managers to put a larger emphasis upon recycling on site. This has triggered a rise in the recycling of all inert materials from site.
Prior to the introduction of the landfill duty just about all construction site waste including bricks and concrete was bulked up and moved to a landfill site for disposal. No consideration was given to recycling. There are now strict limitations 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. Addititionally there is increased recognition of the large choice of potential opportunities to re-use recycled aggregates in the construction process on future construction projects or in areas such as landscaping or home and garden Do-it-yourself. Following the demolition process, together the waste concrete, bricks, masonry etc will 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 impurities 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 contractors will locate a crushing machine on the demolition site, whereas some contractors will prefer to carry the waste to be recycled, back 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 very likely to position a crushing appliance on site to escape incurring extra transportation costs in taking the material back to a sorting and crushing centre.
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The Increasing Demand for Top Quality Recycled Aggregate
Before commencing the crushing procedure, it must be determined what the end product will be used for to ensure that the recycled aggregate is to meet the required standards. There’s huge demand for recycled concrete aggregate to be used within the construction process. As a product, recycled aggregate can be utilised for nearly every type of concrete structural function, road surfacing or pipe laying project. Having passed through the crusher the pieces of aggregate will be separated by size. Bigger pieces can 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 bits of recycled aggregate might be suited to use as a gravel on new construction projects, road laying or driveways at home. The crushing units 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 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 interest in high quality crushed aggregate is growing. There’s key standards in position which are targeted upon improving the recycled concrete aggregate industry. By means of research and improvement, more widespread uses are now being discovered for the employment of recycled aggregate. No more is concrete, just concrete. What we are talking about now are many different 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 high quality grades the 20-5mm recycled aggregate can be used as an aggregate base in highway construction and the quality meets the specifications required to allow its reuse in concrete production. The 20-5mm recycled aggregate is a very versatile product.
On the list of important considerations when you use recycled aggregate is selecting the best specification for your task. For example, when making use of 20-5mm coarse graded aggregate as a road foundation, the thickness of the layer required will have to be determined to withstand 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 used as a road base is that it supports good waterflow and drainage. Once the recycled aggregate is laid, suitable layers of asphalt or concrete can be laid over it to construct the road surface.
In recent years, in the United Kingdom we appear to have more bad weather than hot sunshine and as a consequence the chosen aggregate must have the ability to withstand variances in temperatures and conditions e.g. dampness for long periods, torrential downpours, long dry spells. With its good waterflow and drainage characteristics, the recycled 20-5mm product could be the appropriate 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.
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 Olympic games
In its bid for the 2012 Olympic Games, London set sustainability as the focal point of its bid. The bid team identified a big opportunity to increase awareness of climate change and the issues which encircle it, and bring it to the World’s notice. With the eyes of the Entire world watching, the Olympic Games provide an exceptional opportunity to put across key messages regarding sustainability. Through the entire growth and development of the Olympics project, there exists a commitment to make 2012 the most sustainable Olympics ever held. This focus originated when planning the development and build programmes for the amenities and venues, the transportation links and network, the hosting of the Games themselves and will end by leaving a long lasting legacy of a sustainable natural environment.
Since London was awarded the Games, all companies involved in the development requirements, from the building of the Olympic Arena, the Olympic Village and transportation links between the venues have been encouraged upon guaranteeing the use wherever possible of sustainable resources. Throughout the entire Olympic build programme developers have worked hard to discover practical sustainable materials for use in the build programme. At the end of the whole project there will be some clearly visible 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 many sites will not even think about how recycled aggregates have been employed as part of the overall construction project. However designers and specifiers of materials to be used within the build programme will be comfortable in the knowledge that they have selected sustainable products which include, the most appropriate recycled aggregates as part of the project. With its identified 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.
Summary
How times have changed in recent years in the demolition and construction industry. Firms have needed to adapt to meet tough environmental conditions. As with nearly every segment, new laws and legislation dictate the standards to which your company must aspire, if it is to be successful.
Companies engaged in the manufacturing of recycled concrete aggregate are no 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.