Aluminium may not be a renewable resource, but at the present rate of usage supplies will last another 300 years - and 70 per cent of all the material used is recycled at the end of its product life.
It is, in fact, the most abundant metallic element on earth, making up about eight per cent of the earth's crust, and ranking behind only oxygen and silica as the most commonly occurring. While the process of isolating aluminium from ore does use large amounts of electricity, two-thirds of this power is now generated by hydro-electric power, and therefore without carbon dioxide emissions.
Newly-developed processes for recycling have reduced energy consumption dramatically, without loss of properties, and the material can be alloyed with other elements to achieve specific performance characteristics. It is not uncommon, for example, for recycled building sheets to end up in motor cars (see opposite page).
The essential characteristics of aluminium make it an ideal construction material. It is light, strong, durable and requires minimum maintenance. It is flexible and easy to handle. It can be curved, tapered, welded and cut to the most challenging and dynamic geometries. Where it is cut, the metal's innate resistance to corrosion means that the trimmed edge does not need to be protected.
The natural oxidation creates an ever-present barrier to atmospheric attack. Inert and hard, the oxide protects the underlying metal, reforming spontaneously if damaged or scratched. As an integral part of the metal, this oxide layer thickens very slowly with age and darkens gradually depending on the level of atmospheric pollution.
The most common industrial pollutants, such as ammonia, carbon monoxide and carbon dioxide, all have very little effect. Aluminium performs particularly well in coastal and marine environments because of the minimal effect of sodium chloride.
There are many aluminium alloy compositions available on the market, each with their own specific characteristics and properties. Under normal atmospheric conditions the aluminium alloy 3004 used by Hoogovens possesses high strength, has good corrosion-resisting properties, is easy to work and can be welded. These corrosion-resisting properties are significantly improved with the addition of a weathering layer of aluminium alloy, generally referred to as Alclad.
Hoogovens' Alclad is unique. Registered under the name kal-alloyregistered, it was originally developed for use in the aerospace industry. It consists of a central core of alloy 3004 with a layer of aluminium zinc alloy on both sides.
Tests carried out by the Federal Material Testing Institute (bam) in Berlin show that any corrosive pitting which occurs is restricted to the outer cladding layers, thus preserving the core material far beyond normal life expectations of other materials.
These properties are endorsed by the British Board of Agrement Certificate N. 98/3481. Durability section 10.9 states that the kal-zipregistered roof system will have a minimum service life of 40 years in rural/suburban environments, and 25 years in industrial/marine environments.
According to bs8200 Design of non-loadbearing external vertical enclosures of buildings, 'The durability and design life of the external face of the enclosure and its components should be related to, but not necessarily the same as, the design life of the completed building . . . The designer should, nevertheless, assess as precisely as possible the required minimum life of the enclosure as a whole (with maintenance considered) . . . Components in groups A and B [secondary framing and its fixing, panels and their fixings, thermal-insulating components and materials, vapour barriers and flashings] should have a design life approximating to that of the enclosures as a whole.' This highlights the long-term benefits of Hoogovens' policy of co-developing fixings, insulation and vapour-control layers, together with the in-house manufacture of flashings and fabrications.
It is surprising, therefore, that in a recent survey only 12 per cent perceived aluminium to be a useful building material, behind wood at 44 per cent and steel at 35 per cent. Market research by Hoogovens has shown that this is probably so due to a combination of confusion and ignorance among specifiers and clients about aluminium's actual benefits.
This is likely to change, however, following the publication of the government's recent report on introducing strict criteria of sustainability into construction materials and practice, 'Opportunities for Change: Consultation Paper on a Revised uk Strategy for Sustainable Development', available on the detr website at http://www.environment.detr.gov.uk.
The uk construction industry consumes around 6 tonnes of material per person, per year. The potential for reducing consumption and increasing re-use and recycling is considerable. Materials that are produced cleanly and efficiently, and that are easily maintained with minimum impact on the environment over their whole life cycle, including final disposal, should be the first choice of clients, financiers, developers, planners, designers, contractors, product manufacturers and material producers.
Hoogovens Aluminium Building Systems is both product and material producer by providing aluminium from bauxite, kal-zipregistered from aluminium, and complete roof and wall packages from kal-zipregistered. Aluminium kal-zipregistered is unique in offering choice of re-use or recycling.
There are now projects in both the UK and around the world where kal- zipregistered has been simply unzipped, packaged, transported and re-zipped on to another construction project - a truly re-usable product!
Alternatively, kal-zipregistered, its components, accessories, flashings and fabrications, all of aluminium, can be recycled for only 5 per cent of the original energy consumption for no loss of quality. This saves on the need for raw material and landfill sites for their residues. Aluminium has been recycled in the uk since the 1920s. One of the largest can re-melt centres can be found at Warrington, Cheshire, not far from the Hoogovens Haydock plant.
Some key facts that need to be remembered are that most of the built environment and infrastructure has a long life, so future generations will inherit today's built environment. Sustainability is at least as much about caring for, improving and refurbishing existing buildings as it is about the design and construction of new buildings - that is why we feel that kal-systems are one of the answers to the ecological principles of the built envelope. Being constructed of quality co-ordinated individual components and materials, kal-system for roof or wall can be completely dismantled quickly, efficiently and effectively back into its primary material components, comprising:
all aluminium external skins, flashings and components
rock or glass fibre, slab, semi-solid slab, quilt or cladding roll insulation material
vapour control layer - various forms of sheet material
steel liner sheet, structural decking, flashings and fixings forming the internal elements of the system.
All four major material components from industries with excellent individual track records are capable of being recycled or reused with minimal impact on the environment and waste or residue, and require no difficult separation techniques.
At Hoogovens we try to apply ecological principles to our business as well as our products, and importantly their application:
we try to learn from experience
through our training school we warn others of dangers
waste is minimised as all production scrap is recycled
in our co-ordination of walkways, fall arrest systems, louvres, fabrications and component collaboration with others, we recognise and pursue quality over price always!
our preferred choice to use natural aluminium for the external, or both inner and outer sheet, allows our systems to weather down naturally to suit the environment
our policy or buy-back allows us to re-use, recycle or restore kal-zipregistered.
We believe that kal-systems, using the best of both metals with total emphasis on aluminium for the external weathering skin, falls within the spirit of the cib definition of sustainable construction:
'the creation and responsible management of a healthy built environment based on resource-efficient and ecological principles - and we welcome the Department of the Environment-funded major study which is investigating what sustainable means for uk construction and what it should be in 2010'.
Marketing manager, Hoogovens
This is a tale of two skips. The first one contains three tonnes of scrap steel, currently worth £15 a tonne. Total value: £45. The second skip is the same size, but loaded with three tonnes of aluminium scrap, worth £570 a tonne. Total value: £1710.
The difference in value is a striking demonstration of how world prices for secondary steel have slumped, while aluminium continues to be viable for recycling despite suffering its own price drop from around £800 a tonne.
Britain is the largest exporter of recycled aluminium. Demand has recently dropped, largely as a result of the downturn in economies in the Far East (mainly Japan) and in Russia, aggravated by a two-month strike at General Motors in the us and the strong pound.
But 70 per cent of the aluminium which is recycled is finding its way back into new cars in the form of manifolds, cam covers, suspension wishbones, alloy wheels and even complete engine blocks, maintaining a high level of demand as well as value, especially from the motor industry.
Steel's plight is well illustrated by the value of scrapped vehicles - End of Life Vehicles, or elvs as they are known in the trade. The value of material in the vehicles, mostly made of steel, has dropped from around £50 each last year to £20 each this year.
Roger Twiney, chairman of the Automotive Consortium on Recycling and Disposal (accord), says: 'The economics of the recycling process are highly vulnerable to fluctuations in market prices for raw materials which are, at present, being driven down by global demand turning potentially viable projects into economic loss.'
Despite the fall in the scrap price of aluminium, its value as an investment - in recycling terms - is still high compared with steel.