Ask the expert: Steel reuse – ADC

What are the main benefits of using reclaimed steel sections on construction projects?

The primary drive behind reusing structural steel framing is the reduction in embodied carbon. Current estimates obtained from studies by Symmetrys and supported by findings from the University of Aalborg show that embodied carbon can be cut by 80 per cent in comparison to typical procurement routes. The carbon reduction for reused steel is greater than that of recycled steel as no electric arc furnaces are required to re-melt and re-form the scrap steel. Reusing steel reduces the need for virgin steel as although 98 per cent of steel is recycled, 63 per cent of steel used is virgin steel. Current estimates suggest that the cost of reused steel is lower than new steel, although further studies are required to quantify the savings. Reusing steel has the potential of increasing the design life of buildings as structural elements are more likely to be over-designed due to the availability of materials. This means the building can be more flexible and could have multiple purposes over its lifespan.

Are there any disadvantages?

The main disadvantage of using reused steel is the uncertainty of structural properties. Reused steel is grouped based on the member size and purpose in the original building. From the groups, samples are tested to determine their properties, however, the quality across the group may differ. Another disadvantage is the availability of reused members. Buildings must be designed based on the available stock, but this is subject to frequent changes. A potential disadvantage for clients is the quality of finish achievable on reused steel. The reused steel could have imperfections resulting from minor corrosion or from the dismantling process. This could be undesirable for some clients looking for a seamless finish. New procedures have been put in place for the use of steel from 1932, this increases the risk of existing finishes containing hazardous substances prohibited under current legislation.

Can reclaimed steel be used on all types of building/structure?

Reused steel can be used on all types of buildings except those required to resist seismic action. Another exception is that reused steel cannot be used in structures subject to fatigue or in plastically analysed structures which rely on the formation of plastic hinges.

What checks need to be carried out to ensure that the sections are still fit-for-use and comply with current regulatory/manufacturing standards?

To ensure that reused steel sections are still fit-for-use and comply with current standards, steelwork should be reclaimed in groups of members that have the same form, size, original function, and are from the same source structure. From the groups, representative members can then be tested to determine the structural properties. Groups are limited to 20 tonnes so that uniformity can be ensured.

Can reclaimed steelwork be CE Marked and/or carry other declarations attesting to its quality, traceability, and suitability for reuse?

Assuming the reclaimed steel passes all required tests, it can be CE Marked in accordance with BS EN 1090. Without traceability, the value of the reused steel will be compromised.

Is there a limit to how many times steel sections can be reused?

Providing that the steel sections meet the requirements specified in SCI P427 and P440, there should be no limit to the number of times steel sections can be reused.

How should architects approach the design and specification of reclaimed steelwork?

Architects must have flexible designs as the steel sections are subject to availability. This could result in larger sections being required which would reduce the floor to ceiling height in the building. Aside from flexible designs, only minimal modifications are required to structural calculations when reused steel is used in a construction.

What are the best ways to source reclaimed steel sections and how can specifiers ensure supply/availability for larger projects?

Several tools are in development to increase the ease of using reclaimed steel for new projects. Symmetrys has been working with LSBU to develop FerrousWheel, a tool to automate the process of matching and replacing designed steel sections in a Revit model with a suitable reclaimed steel alternative from reclaimed steel stockists. To ensure availability for larger projects, a large site set for demolition should be identified as early as possible. This allows the demolition contractor to plan the deconstruction appropriately to guarantee that as much steel as possible is available for reuse.

What advice would you give architects when it comes to designing for deconstruction, rather than demolition?

To simplify the deconstruction process, connections should be designed to be accessible, understandable, and standardised so that steel members can be easily bolt blown instead of drop cut. This increases the length of reclaimed steel members. Buildings should also be designed to reduce the plastic deformation to steel members so that they can be reused. Steel members should be clearly marked, and notes should be made regarding documented test results from time of manufacture. Structures that are standard and regular across their design increase the reusability of the structural elements as the number of groups per deconstruction will be reduced. To further ease deconstruction, designers can provide a deconstruction plan outlining load paths and load transfer systems.

For further information, please visit www.symmetrys.com