Introduction
Mention the term demolition to almost any person and the scene that immediately comes to mind is a vision of a building being blown up and collapsing to the ground. Lots of people have stated they would really like to press the button, to detonate the explosive devices which bring a disused property to the ground. On most occasions the thing that comes down, must go up and we are witnessing many dilapidated buildings being razed making way for future development, often during a regeneration project.
For firms who over a number of have developed their business within the demolition of architectural structures, the demolition sector has become considerably more reaching than simply blowing up unwanted buildings. Once the building is demolished the huge task of site clearance will begin and in a world where consideration of the environmental impacts are very high on a good number of peoples agenda, the material residues as a result of demolition ought to be separated for recycling reasons. This will include such resources as steel, wood, plastic, brickwork and concrete.
Almost all of the materials are bulked up and transported to the appropriate recycling plants for reprocessing. Resources such as bricks and concrete can be crushed and turned into a recycled concrete aggregate product available for reuse in the construction of new highways or structures. More and more though, by means of advancements in technological development, residues like concrete to be recycled have to meet a very high specification for reuse in construction projects.
When crushed, the various sizes of recycled aggregate will determine the likely usage potential of the product. Large sizes might be utilised as cosmetic rockery products in landscaping while much finer, shingle like product can be used as a bedding for pipe laying or as a layer in highway construction. Through an growing number of options recognized for the reuse of recycled aggregate, the entire demolition and construction industry is building 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 Concentration on Recycling from Construction and Demolition Projects
In 1996, UK Government added a duty on all waste products going to landfill. The duty is paid out in addition to typical gate charges for waste material being disposed in landfill and since its launch the cost has risen annually. When it was first introduced, the typical level of duty for general wastes being sent to landfill was �7 per tonne and �2 per tonne for inert materials. The duty should persuade commercial and industrial companies and local authorities collecting from properties, to divert waste away from landfill for recycling. In April ’09, the typical level of landfill duty rose to �40 per tonne and it is timetabled to increase each year by �8 per tonne until 2013. The lower rate of duty incurred upon any inert materials going to landfill for example concrete and soils, has remained relatively stable recently and is currently at �2.50 per tonne.
Nonetheless, the weight factor alone of a bulk load of these inert products going direct to landfill will guarantee that the full cost of disposal becomes horrendously expensive and so even in the demolition and construction market, diverting waste from landfill is a priority.
Most companies within the market have extended their business to become demolition and site clearance contractors, to offer the full range of services.
Next time you see a demolition project in progress or pass any construction site during a build programme, it’s clear to see the quantity of waste being generated. If waste material is not in skips, piles of rubble will be stacked high. The placing of rubble waste materials in skips has been a serious issue for waste companies for several years. I have worked within the waste industry, I have seen skip lorries tipped backwards with the cab of the vehicle up in the air, a result of the sheer overloading of waste skips with building site waste.
Each year, the united kingdom generates around 330 million tonnes of waste material and approximately 90 million tonnes of this is coming from building and demolition wastes. This figure has stayed reasonably constant since 2001. About two thirds of this waste is usually recycled or reused in land reclamation or agricultural development projects. Ever since the later part of the 1990s there’s been a gradual rise in the volumes of construction waste materials being recycled and this has been helped by improvements in technology that have led to improved crushing products to create more widespread use of various grades of recycled aggregates. There is a genuine focus upon the UK construction community to encourage greater recycling of waste on site.
In the past few years, the construction sector as a whole has worked hard to persuade construction site managers to place a greater emphasis upon recycling on site. This has triggered a rise in the recycling of inert materials from site.
Before the introduction of the landfill tax all construction site waste including bricks and concrete would be bulked up and transported to a landfill site for disposal. No thought was given to recycling. These day there are stringent limitations across the sector, coupled with an increase in environmental awareness, as well as the commercial benefits in making sure that this sort of waste is recycled. Addititionally there is significantly greater recognition of the large choice of potential opportunities to use recycled aggregates in the construction process on future 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 be transformed into a recycled concrete aggregate.
To recycle concrete aggregate to a high grade and resalable product, it must be completely free from other debris such as wood, paper, card, steel and other general waste materials. The final product must conform to the specifications of British Standard BS 8500. The task of recycling the concrete can usually be achieved in one of two ways. Some demolition companies will install a crushing machine on the demolition site, whereas various contractors will opt to transport the waste to be recycled, back to their own 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 locate a crushing appliance on site to avoid incurring extra transport costs in taking the material to a sorting and crushing centre.
For many demolition projects a typical building demolition contractor needs to complete good assessment of the risks involved.
The Growing Interest in Top 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 satisfy the necessary standards. There’s huge requirement for recycled aggregate to be used during the construction process. As a product, recycled aggregate can be utilised for nearly every form of concrete structural work, road surfacing or pipe laying project. Having passed through the crusher the chunks of aggregate can be separated by size. Bigger pieces may be retained as a decorative product to use in garden rockery projects, or they may be passed back through the crusher to be crushed to a reduced size. The smaller bits of recycled aggregate could 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 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 top quality crushed aggregate is increasing. There’s key standards in place that are targeted upon improving the recycled concrete aggregate sector. By means of research and improvement, more widespread applications are now 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 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 utilised in road construction or at home on driveways. In addition to 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 commencing. In achieving such high 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 criteria when you use recycled aggregate is choosing the correct specification for your task. For instance, when using 20-5mm coarse graded aggregate as a highway base, the thickness of the layer needed needs to be determined to tolerate traffic flows. Traffic flow on a motorway is going to be significantly different to that of a country road. One 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, suitable layers of asphalt or concrete can be laid above it to form the road surface.
Recently, in the UK we seem to have more rain than hot sunshine and therefore the selected aggregate must have the capacity to withstand variances in temperatures and conditions e.g. dampness for very long periods, torrential downpours, long dry spells. With its good drainage characteristics, the recycled 20-5mm product may be the ideal choice for some sand and gravel applications including, pipe bedding, driveways and footpaths, landscaping, plus for use in ready mixed and precast concrete products. With its drainage qualities, 20-5mm recycled aggregate is a versatile product.
Demolition contractors look to produce recycled concrete material as part of the site clearance process, in making the site ready for redevelopment.
Recycled Aggregates and the 2012 Olympics
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 raise awareness of climate change and the problems that encircle it, and bring it to the World’s notice. With the eyes of the World observing, the Olympic Games give an exceptional opportunity to get across key messages concerning sustainability. Through the entire development of the Olympics project, there’s a commitment to make 2012 the most sustainable Olympics ever held. This focus originated when preparing the development and build programmes for the amenities and venues, the transport links and system, the hosting of the Games themselves and will end by leaving a long lasting heritage of a sustainable environment.
Ever since London was awarded the Games, all companies involved with the development requirements, from the design of the Olympic Arena, the Olympic Village and transportation links to 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 locate acceptable sustainable materials for use in the build programme. By the end of the whole project there will be some clearly visible 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. One of those products which visitors to the games and its many venues will not even consider how recycled aggregates are already used as part of the overall construction project. However developers and specifiers of materials for use in the build programme will be secure in the knowledge that they have selected sustainable products which include, the most suitable recycled 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 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.
Summary
How times have developed in recent years for the demolition and construction industry. Companies have needed to adapt to meet challenging green conditions. As with almost any sector, new regulations and legislation determine the criteria to which your business must aspire, if it is to achieve success.
Firms involved in the manufacturing of recycled aggregate are no different. These are generally 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 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 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 to be used in highway construction and driveways.
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