Information Broadsheet
 

Prepared by Stephen Sainsbury architect.

 

Referencing Capral Aluminium’s EcoMetal publications, The EcoCost ecological impact rating system and associated documented research findings, The Centre for Mined Land Re-Habilitation at UQ, and EPA monitoring reports, and a number of industry monitoring sites, the following analysis of the use of Aluminium structural alloy in the building material palette are discussed.
 

Most Aluminium for Australian use is mined in this country and is subject to the stringent environmental controls of the EPA.
 

The Bauxite ore is extracted in a surface mining operation using a regeneration program which results in a high quality post mining rehabilitation outcome. Vegetation in the path of the strip mining process is seed stripped and those amenable species are potted up and held in nursery conditions nearby. The top soil is stripped and winrowed, the subsoil is stripped and windrowed. The overburden is removed and stored. The bauxite ore is stripped and taken to the processing site.
 

The overburden is replaced, the subsoil is replaced and then the topsoil replaced. The nurseried plants are re-planted and the area overseeded with treated native and endemic seedstock. Within five to ten years the land is returned to a high quality restored ecosystem capable of regenerating to original status.
 

The extracted ore is processed to Alumina which is shipped for processing into aluminium. The initial refinement process consumes considerable energy and produces quantities of red mud waste which is difficult to rehabilitate. Current research programs have been successful in washing with seawater then capping these residues in topsoil and revegetating.
 

The Alumina is smelted into Aluminium at the refinery, a process which consumes considerable energy and while having low environmental pollutant output due to its electrolytic nature produces some by-products.
 

Through ongoing process research and refinement, CO2 emissions and other pollutant output have been reduced over the last decade by 82%. The environmental output of the process is still undergoing review and refinement to reduce these levels even further. This can be compared to the steel mining industries almost negligible improvements over the last three decades in both mining and processing.
 

Aluminium can be recycled using only 5% of the energy requirements and none of the pollutant output of the original smelting process. Aluminium is widely re-cycled currently, with between 15 and 25% of all aluminium now on the market coming from recycling. Collection agencies and collection systems are widespread and in place, ensuring easy and simple recycling.

Aluminium has a very long life due to its unusual property of forming a protective "skin"of nearly invisible impenetrateable oxide which prevents further corrosion.  Over 90% of all aluminium every refined into metal is still in use today, compared with an estimated 5-10%  of steel.

Extrusion and forming of aluminium elements is a low energy process with much material not requiring recasting.

Aluminium can be alloyed with a wide array of other metals to create alloys with a range of properties for different uses. Very strong, highly corrosion resistant alloys are available for specification in construction.

Aluminium is extremely light and strong. Half the weight and four to five times the strength of steel, Kg for Kg. This means in any given situation less than half the weight of material is required. As environmental impact in terms of transport, pollutant emissions, energy usage and so on are all based on the mass of material required to perform the given task, the light weight of the material has critical environmental advantages. 

Much less material is required to perform the same structural and cladding tasks.

The material can be handled in factories and on site without the need for heavy lifting machinery and the extra energy costs or environmental impact associated with those requirements. A six metre long, 215x80mm I Beam can easily be lifted by two people. On site erection of large scale frames is substantially easier, cheaper and safer than steel or other large span systems, requiring much less energy.

Cutting and shaping can be done with normal builder's power tools using special blades, without the need for hot gas or laser cutting at very low energy cost.

Fabrication using MIG and TIG welding can be done on low energy settings creating strong permanent, predicatable weatherproof and corrosion resistant bonding. Latest technology allows on site fabrication to be done safely, cheaply and testably.

Aluminium is naturally corrosion resistant due to its unusual surface self coating properties. It does not require surface treatments, priming, painting or protection from the elements. Welds are stable and self protecting ensuring long term reliability. A range of surface patinas can be created using mechanical post fabrication techniques.

Aluminium has a high surface reflectivity in the Infra Red spectrum up to 70% of all incident heat is reflected with only moderate visible light glare. These properties can be used to substantially improve the thermal performance of building elements

An EcoCost analysis taking into account all of these factors gives a environmental impact value for aluminium of less than a quarter for that of steel and considerably less than that for plantation timber to perform the same task.  In any situation where minimal impact materials such as rammed earth and site milled timber are not available, Aluminium Alloys rapidly become the least environmentally harmful and most flexible material available.

 

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