Proving steel’s green credentials
Part of a portal framed building manufactured by Severfield but never constructed was reused by Cleveland Steel and Tubes for a new warehouse for National Tube Stockholders in Thirsk
The steelwork sector is keen to promote the material’s sustainability credentials, chiefly its potential for reuse or recycling, but there are barriers to overcome. Neil Gerrard explains.
It may be because of its strength and durability that steel doesn’t seem at first glance to be all that “green” a material.
The steel sector is keen to promote how reusable and recyclable the product is. An estimated 650 tonnes is recycled annually, making it the world’s most recycled industrial material. Some 93% of structural steel gets melted down and recycled, with 7% reused, according to a European Steel Association survey.
Michael Sansom, a chartered environmentalist who heads up the Steel Construction Institute’s (SCI) sustainability division, thinks that reuse of steel in construction (taking steel sections from old structures and placing them in new ones) could be more widespread – and says the industry is working hard to address this.
The case for weathering
So-called “weathering steel” is sustainable in the sense that it requires no painting or maintenance throughout its lifetime.
It is more commonly found on bridges, but architect Eric Parry found a different use for it at London’s Pancras Square.
Four Pancras Square is an 11-storey commercial building that uses two different framing solutions. While essentially concrete-framed, the building employs a huge storey-high Vierendeel truss that encircles the building at first floor level and allows the creation of a 27m-long, column-free facade along the building’s main entrance elevation.
Steelwork contractor Severfield fabricated the truss and brought it to the site in 18 sections, with the heaviest weighing 72 tonnes.
Not only will the weathering steel not require any maintenance, it recalls the look of the Victorian gasholders once found on the site.
“Reuse does happen but there are challenges,” he explains. “The current structural steel supply chain is very slick and fast with just-in-time deliveries, and increasingly workshops are automated so putting old sections and stiffeners through them with
holes in and cleats and stiffeners welded on to them is a problem.”
The SCI recognises that there are significant barriers to reuse and recently completed two national research projects with the University of Cambridge to identify solutions.
Chief among these barriers is the availability of reclaimed sections in the desired size, volume, and in the right place at the right time.
Then there are issues relating to quality, traceability and certification, as well as additional cost, a lack of supply chain integration, the additional time requirement, a lack of skills and experience among construction firms in reclaiming and reusing steel, and a perception that reclaimed steel is somehow inferior.
Simply not knowing where the steel needed to complete a job is located is a particular challenge, says Simon Bingham, chairman of structural steelwork contractor Caunton Engineering.
“We need to know where all the steel that is potentially reusable is located, so an asset base of steel structures with all the data in it would be a good start,” he explains. “That’s relatively doable when you consider that most steel structures in the UK now come out of BIM models.”
The SCI is developing a portal that contains a database of BIM models of UK steel-framed buildings, which allows demolition contractors to assess how much steel is in a building and where, and lets designers design new buildings with the knowledge of what is available.
The site currently only exists in prototype form but Sansom hopes to develop and commercialise it.
Meanwhile, the EU projects Reduce” and “Progress” are developing non-destructive testing techniques and demountable shear connectors to aid reuse from composite floors in multi-storey buildings.
Another area Sansom and his colleagues are looking at is extendable, reusable connections for steel beams.
How sustainable is steel construction?
Finally, there is increasing interest in reusing entire structures. For, example, RG Carter and steelwork contractor AC Bacon constructed an aviation academy at Norwich International Airport using a refurbished steel-framed hangar. The 1930s steel lattice truss roof structure and columns were restored while the external envelope was refitted. The project was completed last year.
In a more unusual example, Cleveland Steel and Tubes (CST) bought part of a portal framed building which had been manufactured at Severfield’s Thirsk facility but never built after the order was cancelled in 2008. CST used the steelwork to erect a new warehouse for National Tube Stockholders (NTS) at its neighbouring site in Thirsk in 2017.
The economic case for reusing steel is strong. In March, steel contractor Billington reported that the price of constructional steel had risen 40% in the last two years.
Meanwhile, the value of scrap steel remains low. The University of Cambridge and SCI study revealed that the price difference between new sections and scrap sections averaged £313 per tonne between 2000 and 2016.
Sansom says: “Reuse today has its challenges – but we can make things easier by using BIM and by designing systems that are inherently demountable.”