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Introduction

Mention the term demolition to almost anyone and the scene that instantly comes to mind is a vision of a building being blown up and collapsing to the floor. A lot of people have claimed that they would really like to push the button, to trigger the explosive systems which will bring a disused structure to the ground. Most of the time what comes down, must go up so we are witnessing many dilapidated properties being razed to help with making way for future development, generally together with a regeneration project.

For organizations that over a number of have established their business around the demolition of buildings, the demolition arena is now considerably more reaching than just blowing up unwanted buildings. When the structure is demolished the massive task of site clearance begins and in a world where consideration of the environmental effects are ever increasing on most peoples agenda, the material residues as a result of demolition have to be separated for recycling purposes. This will likely include such materials as steel, wood, plastic, brickwork and concrete.

A lot of the materials are bulked up and transferred into the appropriate recycling plants for reprocessing. Materials such as bricks and concrete are generally crushed and become a recycled concrete aggregate substance completely ready for reuse in the construction of new roads or structures. More and more though, through breakthroughs in technological development, residues like rubble to be recycled have to meet a high specification for reuse in construction projects.

When crushed, the different sizes of recycled aggregate will govern the future usage potential of the product. Larger sizes could be utilised as ornamental rockery products in landscaping whilst much finer, shingle like product may be used as a bedding for pipe laying or as a layer in street construction. Through an increasing number of possibilities recognized 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 tax on all waste items going to landfill. The duty is paid on top of normal gate charges for waste materials being disposed in landfill and since its initial release the charge has increased on an annual basis. When it was first introduced, the typical level of duty for general waste materials being sent to landfill was �7 per tonne and �2 per tonne for inert materials. The duty was designed to inspire commercial and industrial firms and local authorities collecting from households, to divert waste away from landfill for recycling. In April 2009, the standard rate of landfill tax increased to �40 per tonne and is also scheduled to increase every year by �8 per tonne until 2013. The lower level of duty incurred 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.

Nonetheless, the weight factor alone of a bulk load of these inert materials going straight to landfill will ensure that the entire cost of disposal becomes extremely expensive and so even in the demolition and construction sector, diverting waste from landfill is a priority.

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The next time you see a demolition project in progress or go past just about any construction site during a build programme, it will be clear to see the amount of waste materials being created. If waste material is not in skips, heaps of rubble will be stacked high. The placing of brick waste in skips has been a major problem for waste contractors for several years. Having been an employee in the waste industry, I’ve seen skip trucks tipped backwards with the cab of the vehicle up in the air, a result of the sheer overloading of waste skips with construction site waste.

Every year, the uk generates around 330 million tonnes of waste and approximately 90 million tonnes of this is coming from construction and demolition wastes. This figure has remained reasonably steady since 2001. About two thirds of this waste is usually recycled or reused in land reclamation or agricultural development projects. Ever since the late 1990s there’s been a gradual increase in the quantities of construction waste being recycled and this has been assisted by improvements in technology which have resulted in improved crushing technology to create more widespread use of varying grades of recycled aggregates.

In recent years, the construction sector in general has worked hard to persuade construction site managers to put a greater focus upon recycling on site. This has resulted in a rise in the recycling of all inert materials from site.

Prior to the introduction of the landfill duty almost all construction site waste material including bricks and concrete was bulked up and transported to a landfill site for disposal. No regard was given to recycling. These day there are strict limitations across the sector, coupled with an increase in environmental consciousness, as well as the commercial benefits in ensuring that this sort of waste is now recycled. There is also greater recognition of the wide array of business opportunities to re-use recycled aggregates within the construction process on future construction projects or in fields 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 needs to be completely free from other contaminants such as wood, paper, card, steel and other general waste materials. The end product must comply with the requirements of British Standard BS 8500. The process of recycling the concrete can normally be achieved in one of two ways. Some demolition contractors will transport 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 occur at the same location, the contractor is very likely to position a crushing machine on site to avoid incurring added transportation costs in taking the material back to a sorting and crushing centre.

For all demolition projects a typical building demolition contractor should complete a comprehensive assessment of the hazards involved.

The Increasing Need for Top Quality Recycled Aggregate

Before starting the crushing process, it must be determined what the end product is to be used for to ensure that the recycled aggregate is to satisfy the required standards. There’s huge requirement for recycled aggregate to be used back in the construction process. As a product, recycled aggregate can be utilised for just about any type 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 may be retained as a decorative product for use in garden rockery projects, or they might be passed back through the crusher to be pummeled to a reduced size. The small bits of recycled aggregate may be suitable for use as a gravel on new construction projects, road laying or driveways at home. The crushing units 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 top quality crushed aggregate is growing. There are key standards in place which are concentrated upon improving the recycled aggregate sector. By means of research and improvement, more widespread applications are being identified for the employment of recycled aggregate. No longer is concrete, just concrete. What we are talking about now are many distinct grades of recycled aggregate, ranging from the large sections 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. As well as being used as a mix for highway construction, recycled aggregate is being used as bedding for pipe laying or base 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 road 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 the important considerations when using recycled aggregate is choosing the right specification for the task. For example, when making use of 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 reason aggregate produced to a 20-5mm specification is employed as a road base is that it assists good drainage. Once the recycled aggregate is installed, suitable layers of asphalt or concrete can be laid across it to build the road surface.

Recently, in the UK we seem to have more bad weather than hot sunshine and as a consequence the selected aggregate must have the capacity to tolerate variances in temperature and conditions e.g. dampness for long periods, torrential downpours, long dry spells. With its good waterflow and drainage qualities, the recycled 20-5mm product could be the appropriate choice for many 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 flexible product.

Following demolition, contractors will use crushing machinery to produce recycled concrete aggregates from the waste bricks and concrete for use in future construction processes.

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 significant opportunity to raise awareness of climate change and the challenges which surround it, and bring it to the World’s notice. With the eyes of the World watching, the Olympic Games give an exceptional opportunity to put across important messages about sustainability. During the whole growth and development of the Olympic project, there’s a commitment to make 2012 by far the most sustainable Olympics ever held. This focus began when planning the design and build programmes for the amenities and venues, the transport links and system, the hosting of the Games themselves and will conclude by leaving behind a long lasting heritage of a sustainable healthy environment.

Since London was awarded the Games, all companies involved in the development requirements, from the construction of the Olympic Arena, the Olympic Village and transport links between the venues have been focused upon ensuring the use wherever possible of sustainable materials. Across the entire Olympic build programme developers have worked hard to locate acceptable sustainable materials for use in the build programme. By 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. One of those products which visitors to the games and its countless locations won’t even consider how recycled aggregates have been employed as part of the overall construction project. However designers 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 concrete aggregates as part of the project. With its recognized qualities, let us hope that somewhere in the world wide TV coverage the 20-5mm recycled aggregate gets a mention somewhere, somehow.

Summary

How times have developed in recent years for the demolition and construction sector. Firms have been required to adapt to meet challenging green specifications. As with nearly every market, new laws and legislation dictate the criteria to which your business must aspire, if it is to be successful.

Businesses engaged in the production 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 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. The demolition and construction industry now places sustainability at the forefront of its future development projects.

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