Steel everlasting
Industry positioning steel as essential to sustainable building
by Sylvie Boulanger
With its long history of recycling, the steel industry has engaged in sustainable practices even before there was a conscious movement to do so. Today, the industry is trying to make its products an essential part in the holistic design of buildings that conserve energy, have superior indoor environments, and that can be refurbished or re-erected for use long into the future.
Strong claims can already be made:
» Steel is 100% recyclable, and can be recycled infinitely without affecting its properties,
» More steel is recycled than paper, aluminum, glass and plastic combined,
» Steel contains no glues or additives, and
» Steel does not release any chemicals.
The large issues for the steel industry in the area of sustainability include: energy and CO2 emissions, re-use, and thermal mass.
Energy and CO² Emissions
According to the Canadian Steel Producers Association [CSPA], the amount of energy required to produce a tonne of shipped steel decreased by 26% between 1990 to 1999. And steel producers have made a commitment to achieve further energy savings of 1% a year.
On the manufacturing side, many steel specialty contractors have modernized facilities to include paint recovery, and scrap recycling bins; and numerically-controlled operations that improve energy efficiency.
On the emissions side, CSPA members’ investment of more than $200 million a year in environmental technologies has delivered CO² reduction of 16% from 1990 to 2003. Making one tonne of steel today produces 80% less emissions overall than
a decade ago.
More work in this area is a priority. Canadian steel companies, for example, participate in the CO2 Breakthrough Program of the Brussels-based International Iron and Steel Institute [IISI]. Initiated in 2003, the global program uses research projects to identify potential breakthrough technologies and revolutionary processes for making steel with radically reduced CO2 emissions.
Recovery: Recycle and Reuse
Steel recovery can include recycling into other structural steel members, reuse of steel elements in another building, reuse of the steel structure in situ, or even its dismantling and re-erection on another site.
Steel is the world’s most recycled material. In North America alone, over 70 million tons of steel are recycled annually or exported for recycling annually. The overall steel-recycling rate in Canada is more than 65% and growing at over 2.5% a year.
The Steel Recycling Institute claims that up to 95% of structural beams and plates, and 50% of reinforcement bars are recycled. And even though new virgin steel is needed to meet demand unfulfilled by available scrap supplies, two out of every three kilograms of steel produced today are derived from ‘old’ steel.
Reuse could be the next breakthrough once the logistics of supply are worked out. Recovery of steel from demolition sites is fairly straightforward provided it is not contaminated, or has other material attached, as in the case of rebar.
Second-hand steel can come from a steel service centre, a fabricator’s yard or from a demolition site, and consists mainly of W-shapes and angles, some tubular sections, and occasionally joists. Structural engineers who keep close contacts with demolition companies can help source reused steel. Ideally, the reused steel should be sourced first, with the structural framing layout then based on the available sizes.
Many steel structures are bolted, making them relatively easy to dismantle. Steel erection specialists rather than demolition crews should dismantle and erect the structure at a new location. Designing for deconstruction is not yet an established practice but is being done, and will become a natural part of sustainable design. Already some specific standards addressing these issues are being considered by the Canadian Standards Association.
Sylvie Boulanger, P.Eng. Ph.D is a staff member of the Canadian Institute of Steel Construction and executive director of the Quebec region.
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Quality of reused steel
Steel from as far back as the 1910s can be reused, however, steel from the 1950s or earlier and containing higher carbon, may require modified welding procedures. A mill test certificate or a coupon test verifies the quality of the steel. A mill test certificate for a batch of steel describes the chemical and physical properties of the steel, and should be retained as it is valid for many years. Without a mill test certificate, a small sample or coupon of the steel will need to be tested for weldability, and for yield and tensile strength, a process that costs from $500 to $1,000.
Recycled content of steel vs. process
The integrated mill produces steel with the BOF [Basic Oxygen Furnace] while the mini-mill’s process is based on the EAF [Electric Arc Furnace]. The BOF uses 25% recycled steel [up to 35%], and the EAF is fed 90% recycled steel [up to 100%]. Adding the post-consumer and half the post-industrial recycled contents will generally provide a 15-20% LEED™ value for a BOF and 75-80% for an EAF. In general, each process is responsible for about half of the steel products on a project. For example, most shapes emerge from the EAF, and derived plate products from the BOF.
Web references
Canadian Institute of Steel Construction, www.cisc-icca.ca/green
Canadian Steel Producers Association, www.canadiansteel.ca
Canadian Sheet Steel Building Institute, www.cssbi.ca
Reuse Steel, www.reuse-steel.org
Steel Recycling Institute, www.recycle-steel.org
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U of T Scarborough Campus Student Centre
Supply, design flexibility key to steel reuse
by Mark Gorgolewski
The University of Toronto Scarborough Campus [UTSC] Student Centre, a three-storey, 4,700 m2 facility built in 2004, contains approximately 300 tonnes of structural steel. Just under 5% of that came from the Royal Ontario Museum’s [ROM] old Terrace Gallery, deconstructed to make way for Daniel Libeskind’s angular, glazed addition.
From the start, the client proposed sustainability goals based on LEEDTM that the design team developed into a strategy for the application of reused materials, particularly structural steel.
Suitable salvaged steel was not available from demolition projects or salvage yards. Luckily, structural engineers Halsall Associates Limited identified the demolition at the ROM as a source of crushed concrete for reuse as backfill and aggregates, and of wide-flange steel components found in a one-storey deep, long-span truss. The ROM and its designers supported salvaging the materials as long as the process did not interfere with the construction schedule.
The original structural drawings of the ROM wing were available to affirm the structural characteristics of the steel. The steel truss was separated from the composite floors it supported, and torch-cut, not sheared, to retain the largest useful lengths possible and to reduce the risk of damage.
To minimize cost and environmental impact, the steel components went directly from the demolition site to the fabricator for cleaning, refabrication and painting. The components had not been fireproofed, and the fabricator required little extra time for the cleaning process.
The reused steel components were treated no differently than the new steel. Their fabrication with bolt connections offered a single method for construction, and convenient deconstruction and further reuse down the road.
The wide-flange steel sections of the original one-storey truss were reused as both columns and beams in the student office wing. The available sizes dictated the design of the structure, which resulted in deeper beams and some over-design. Consequently, the structural framing was redesigned, and the beams rotated 90 degrees to fit the ductwork within the ceiling depth.
Deconstruction and delivery of the salvaged steel to the fabricator cost about $5,000, with an additional $6,000 or so for fabrication. These costs compare favourably with the $12,000 to $15,000 for new steel, and will likely fall as better supply and work flows become established.
The amount of salvaged steel was less than the 5% minimum required for the LEEDTM Resource Reuse credit. However, Stantec Architects Limited are applying for the Innovation & Design Process credit that aims to support green building design initiatives, such as the successful reuse of steel, not included in the existing rating scheme. The architects anticipate that the project will achieve a LEEDTM silver rating.
More details on projects containing salvaged steel are found on the web site: www.reuse-steel.org .
Credits
- Client: University of Toronto Scarborough Campus, Student Centre
- Architect: Stantec Architects Limited, [formerly Dunlop Architects], Toronto
- Structural engineer: Halsall Associates Limited, Toronto
- Mechanical engineer: Stantec (formerly Keen Engineering), Toronto
- Contractor: Walter Construction Corporation, Toronto
- Steel fabricator: Mirage Steel Limited, Toronto
- Photo: Stantec Architects Limited
- Project cost: $14 million