Steel and sustainability 2: Recovery strategies
The long unedited version
17 mars 2004

by Sylvie Boulanger and Sylvain Boulanger

This second article addresses Recovery strategies. A short version appeared in Canadian Architect in March 2004. It followed Steel and sustainability 1: Integration (see Canadian Architect January 2004 issue) where the ripple ‘green’ effects of using steel were discussed – in terms of how using steel can help other building components achieve their best LEED™ Rating in their respective categories (seemingly not associated to Materials & Resources).

This time the unique nature of steel as a building material (and its infinite life) is reviewed – in terms of recovery. This article addresses in more depth the topic of recovery than was possible in Canadian Architect by developing the questions below, and concluding with suggestions for the future.

What exactly do we mean by recovery?
What is the inherent recycled content of steel?
How can one obtain the recycled content of a steel product?
How easy is it to recover steel for recycling?
What about the quality of steel once recycled?
How can one be sure of the quality of the reused steel?
Where does one find "second hand" steel?
When can one consider reusing a steel structure "in situ"?
What are some recent examples of steel reuse?

• Old Angus beam gets a second life in the new Chapiteau des Arts du Cirque
  
• Bits of the ROM become pieces of the University of Toronto Student Centre
  
• An old warehouse becomes Baie St-Paul's new Town Hall
  
• The Eaton Building becomes Le Complexe les Ailes

Recovery implies reuse of an existing structure or recycling of steel products, extending the sustainable life of a structure and the material through multiple recovery cycles, thereby honouring the "from cradle to cradle" concept. Reusing steel involves both reusing steel in situ, dismantling a structure so it can be rebuilt elsewhere or reusing steel members and elements from a demolition site for a new building. Recycling means taking the steel members from an old structure or steel from defunct automobiles, appliances and industrial wastes, and making new steel from it, by re-melting in a furnace. Recovery strategies should be considered not only at the end of a structure's life, as it is commonly done, but they should be integrated from the onset during the conceptual phase i.e.: What will the second life of the structure be? What will be recovered? Will it have a third and fourth life? What must be integrated at the design stage to facilitate recovery? And where would one start if one wanted to bring in reused steel in a project? By searching some kind of a large warehouse specialized in storing and selling reused steel, accessible through a web interface? That's for the future. Today, your best sources are the next demolition sites, and your engineering partners.

What is the inherent recycled content of steel?

It depends on the process and the calculation method. Two contemporary technologies are used to produce steel: the basic oxygen furnace (BOF) and the electric arc furnace (EAF), which integrate old steel to make new differently. The BOF consistently uses 20 to 25% of recycled content (up to a maximum of 35%), and generally provides recovered steel for products such as automotive fenders, refrigerators, soup cans, high-volume drums. The EAF consistently uses 90% of recycled content (up to nearly 100%, in some cases) and yields products such as structural beams, steel plates and reinforcement bars. The reason the recycled content calculation for the EAF will vary depends mostly on the process and the method of calculation. When you start an EAF cold, all the input material comes from recycled content. However, after the first batch, the amount of liquid steel left in the ladle may represent up to 10% of the original content. Should one now consider this leftover as recycled steel or new steel? Also, some mills may have both types of furnaces. Hence, a small amount of the input material for the EAF may come from a BOF, decreasing the recycled content of the new steel. After describing both processes, one should note that they are both needed. You will see later that the recycling rates of cars, buildings and industrial materials are very high which means that at the moment, the demand cannot be entirely met through recycling. Also, as we indicated in the previous paper, once steel is in the loop, there is a very high probability that it will stay in it. Steel rarely gets crushed and left out to die as fill. The infinite life of steel as a material and its ability to take new forms and serve new purposes is illustrated by the fact that more steel is recycled annually than all other materials – including aluminum, glass and paper combined. Unlike other industries that are making an entry into the process of recycling, the steel industry has been doing it for decades. Scrap processors and auto dismantlers have been around for nearly a century.


How can one obtain the recycled content of a steel product?

The Steel Recycling Institute has a letter addressed to architects and engineers, on their web site (www.recycle-steel.org/leed), providing a fact sheet and a calculation according to the LEED™ requirements, which decomposes the recycled content in terms of post-consumer and post-industrial products, and uses the proper LEED™ coefficients. In Canada, Dofasco has a similar fact sheet on their web site stating a recycled content of 88,1%. For the University of Toronto Student Centre, the fabricator Mirage Steel was able to contact the service centre from which the steel was purchased, who explained that those steel sections came from Steel Dynamics, which only uses EAFs. Obtaining the value was not too difficult in that case. However, the industry needs to be able to trace the material back to its origin with more ease, and provide better access to information by architects and engineers, than is presently the case. As a general rule, if you have purchased a W shape (beam or column) from North America, you can almost be certain that the recycled content rating will exceed 90% as most of these shapes are produced in EAFs. If you use tubular sections (HSS), the chances are high that the coil used to produce HSS will be the result of an EAF process but they could also come from a BOF. In a scenario where all of the structural steel comes from North America but cannot be traced back to a mill, one can still conservatively use 20 to 25% recycled content. If you do start a green building project, make sure the information is transmitted to the fabricator early on so that the necessary measures can be applied during purchasing.


How easy is it to recover steel for recycling?

Although the answer depends on the initial site, in general the skeletal and dismountable nature of a steel structure facilitates the process. In an unusual situation such as the steel from the World Trade Center twin towers – 95% of structural beams and plates were recovered, and 50% of the reinforcement bars. Incidentally, these ratios correspond to the estimated recycling rates of both of these products according to the Steel Recycling Institute. When recovering cars, some shredders can reduce an automobile into small chunks in 45 seconds, or approximately 80 to 100 cars per hour! In 2001, 14.5 million cars in the US nurtured the open loop of recycling this way. In fact, approximately 96% of all steel from automobiles is currently recycled. Steel is collected not only from used auto parts yards, but also from demolition sites and industrial manufacturers for sorting, weighing and mechanical treatment. Companies such as SNF (Société Nationale de Ferrailles) specializing in the recovery of steel, rely on electromagnetic cranes, powerful guillotine shears and huge machinery for sorting, shredding, shearing, crushing and reducing metals to bits, pieces or fragments. Recovery of steel from demolition sites is fairly straightforward if it is not contaminated, or that no other material is attached. [insert ROM picture] However, when material is attached, such as concrete on rebars, more energy is needed to extract, transport and clean, compared to the equivalent in structural beams or plates, which is why the recovery rate of rebars is about half of that of steel beams and girders. Once the steel has been reduced, compactors and other machinery then turn the raw material into bales, briquettes or granules.


What about the quality of steel once recycled?

The quality of the recycled steel is as good as the current material standards. With some exceptions, a variety of post-consumer and post-industrial steel products can be mixed without sacrificing the quality of the "new" steel. First of all, time is not a factor. The differences in impurities, mostly carbon, between old and new steel is small, and carbon can be factored out during production. Second, testing is ongoing during the process of making steel. There is a continuous monitoring device used to control the residual content in steel – in particular the content of carbon, manganese, sulfur and phosphorous. Before the heat is tapped, that is before liquid steel leaves the furnace, a final adjustment is made. Third, the unique magnetic properties of steel reduces the potential errors of introducing other metals. In other words, ferrous scrap can be sorted from non-ferrous scrap using magnets! Finally, mills will not accept high-risk scraps, such electric motors, radioactive elements, heavy metals, or any material, which has a high residual content of lead or copper. To summarize, some recipe adjustments may be needed depending on the source, and traces of impurities may differ. However, unlike other construction materials, whether a structural steel product is made from 35 or 100% recycled content, the quality as dictated by current material standards, is the same, and can be recycled ad infinitum.


How can one be sure of the quality of the reused steel?

The quality of the reused steel is provided by a mill test or results from a coupon test. Any batch of steel produced today comes with what we call a "mill test". A mill test gives you important information about the chemical and physical properties of the steel. If you have a mill test, even a few decades old, which meets today's required chemical and physical performances, testing is not needed. If your strength requirements are not too high, you can always rely on a clause in the steel standard, which specifies that the yield capacity used to calculate the resistance of unidentified steel shall not exceed 210 MPa, which is a conservative value. You will want to test the steel if you need to know two criteria: weldability and strength. By weldability, we mean that we can attach reinforcing steel elements through welding. By strength, we mean the yield strength and the ultimate strength of the steel. If you are only concerned about weldability, you may decide to have just the chemical test performed. However, if physical testing is required, you will need to take one or more samples of the steel, called "coupons", which are rectangles of about 1 foot long by 2" or 3" wide. It is important to note that the recycled content of the reused steel cannot be determined through testing. Perhaps traces of certain impurities might give you hints but that is not a reliable measure. With regards to steel performance, the homogenous nature of steel allows the information coming from a coupon test to assess the capacity of the steel within the high-level of confidence of current standards.


Where does one find "second hand" steel?

Either from a warehouse, a fabricator's yard or more likely, from a current or future demolition site, or from a structural engineer who makes it a habit of tracking previous projects. Some steel service centers have made it their business to hold "second hand" steel, which now might represent approximately 10% of their inventory. The second hand steel inventory consists mainly of W shapes and angles, some tubular sections, and occasionally joists. Through close contacts with demolition companies, one can pre-select some members which are retained strictly through a visual assessment based on experience. However, one cannot expect to call a service centre, ask for 10 identical I-beams of a specific length and specific strength, and have it delivered the next day. Although the major motivation for holding "second hand" steel is the cost – approximately half the cost of new steel – the possibility of reuse for obtaining LEED™ points is promising, even if at this point the option appears more feasible for smaller projects. What about joists? Although Canam, the largest open web steel joist manufacturer in Canada, held an inventory of old joists in the US years back, the lack of interest for such a product prompted them to abandon the project. This situation may change again in the near future. With regards to the reuse of joists, one's best chance is to have good contacts with demolition crews before a building is torn down, and make sure the joists are handled with care. One suggestion is to find the used joists first, and then finalize the layout according to the available lengths instead of vice-versa – a lesson learned from the Mountain Equipment Coop project in Montreal. However, engineers from Saia Deslauriers Kadanoff were still able to integrate reused tubular sections for the fabrication of the main trusses and the climbing sculpture. If possible through the project procurement method – one should consider asking what is available to the fabricators involved in the project (possibly another member of the early integrated design process).

When can one consider reusing a steel structure "in situ"?

It depends on the condition of the original steel, the age of the structure, the information you have from archived drawings, and whether you need to reuse it "as is", retrofit it to satisfy current seismic criteria, or reinforce it through welding. In all cases, you will want to test any steel whose mill test cannot be traced if you want to use the maximum material properties. Data about where the steel was produced, what standard it originally satisfied, and what year it was in use – all help the engineer assess the structure. It is interesting to note that historically – the steel industry made technological leaps as early as the turn of the 20th century. Hence, as far back as the 1910s, steel was already a relatively homogeneous and reliable material, and for that reason, steel of that vintage can still be reused today. On the other hand, concrete became an improved building material only after the 1950's, and that is one of the reasons why there are fewer concrete buildings or bridges before that period that can be reused or refurbished without major rework. The testing company X-per-X says that steel coupons from older structures are regularly tested, and rarely assessed as unusable. The most concern engineers have with steel produced prior to the 1950’s is its weldability, because of the higher carbon content present in many of the grades produced during those years. What may happen is an adaptation in the welding procedure, but the steel is not often declared unweldable or otherwise inadequate. Incidentally, X-per-X and today's engineers find that engineers of that era tended to design "adult" size columns and beams, that is, heavier sections were employed creating a reserve capacity compared to the newer lighter designs. What can sometimes be more difficult with the steels of that era is obtaining the proper dimensions for calculating their capacity. Fortunately, reusing steel since the turn of the century is relatively common and a guide published by AISC indicates sizes, yield strengths and other useful information for rehabilitation purposes. Steels produced after the 1950’s generally pose few problems, except that the yield strength might be lower. As mentioned previously, steel made after 1910 can at minimum be recycled, independent of carbon content.


What are recent examples of steel reuse?

The Eaton building in Montreal becomes Le Complexe les Ailes
(date of reused steel: 1920’s – 1950’s)
In 2002, Lemay & Associés took the Eaton building in Montreal and refurbished it into the new and elegant Complexe les Ailes. Although part of the structure was gutted to create an ovoid atrium, much of the structure was reused. Most of the steel, which dates from several eras, ranging from the 20's to the 50's, could be reused – as concluded by the engineering firm Pasquin St-Jean which had coupons of the steel tested for its yield strength, and carbon content. It turns out that the low yield strength of that period could be compensated by the fact that many of the members were oversized, a common practice for that period. Even the columns could be reused. Although the steel had higher carbon content than the new steel, it was still possible to weld onto it. The top floor was reinforced, as its structure was the former roof. The roof was refurbished as a floor, necessitating extra joists between the existing ones. As far as the rest of the building is concerned, a major portion of the complexity was due to problems with interfaces between different parts of the building built at different periods, and the new parts, complicated by non-typical geometries. The team explained that they would have all benefited from more extensive visual assessments and testing earlier in this fast-track project.

An old warehouse becomes Baie St-Paul's new Town Hall
(date of reused steel: 1960’s)
Anne Carrier Architectes were retained by the City of Baie St-Paul for their new Town Hall. In 2003, the architects created the required signature space from an old industrial building built in the 1960’s. With the exception of one corner of the building, which once endured a fire, all of the steel was reused. Several coupons tested from different locations revealed that the yield strength employed at the time of construction could be taken for calculating the resistance of the members based on current standards, and that welding would not be a problem. There appeared to be several sources of steel – one of which originated in Britain – which prompted the engineer to test in different locations. Much of the steel is left exposed inside, including the roof joists, and traces of the past were deliberately left untouched on many of the columns.

Bits of the ROM become pieces of the University of Toronto Student Centre
(date of reused steel: 1970s)
In 2003, Dunlop Architects were asked by University of Toronto students, who are members of the building committee, to provide a building that reflected a sustainable approach for their new Student Center. In fact, the students did not understand why such an approach was not adopted by default for all buildings under construction today. Dunlop Architects and Halsall Engineers came up with the idea that part of the material could come from existing sources. Halsall, who is presently working on demolishing part of the ROM building, proposed reusing ROM girders for the new Student Centre. Since Halsall had done that part of the ROM building in the late 1970s, they had all the necessary archives for demonstrating the material quality of the steel to be reused – therefore no testing was required. The most testing challenge however, was for the architect to find the right official from the ROM building to speak to the right University of Toronto official, for accepting the (donated) steel. This administrative aspect had to be factored into the project scheduling of this reuse. The reused steel amounted to approximately 18 tons of saved steel.

Old Angus beam gets second life in the new Chapiteau des Arts du Cirque
(dates of reused steel: several)
In 2003, Le Cirque du Soleil retained the proposal by Schème, and Jodoin, Lamarre, Pratte & Associés, in part for their sustainable development concept for the design of the Chapiteau des Arts du Cirque. With an opening date planned in June 2004, the building is almost finished. The intention to integrate reused steel was part of the green building view of the project. Some promising options seemed possible with steel available from two fabricators. For different reasons, one of which was timing, the structural engineer Martoni Cyr et Associés found the required steel elsewhere, at Panzini Demolition. In this project, the engineers only needed a chemical test, to verify the weldability of the steel, relying on the lower allowable yield stress for unidentified steel as permitted in the steel construction standard. One of the recovered beams still had rivets. Interestingly, the reused beams of the Chapiteau are left exposed, and in their original state, reflecting the historical character of the steel beam and thereby sensitizing visitors to material reuse For example, one of the exposed beams came from one of the Old Angus shops in Montreal and was left "as is". The reused steel for this project was purchased through a new acquiring process, as this was a relatively 'non-standard' order.


How does one go about testing steel for reuse? Is it expensive?

One needs to cut out a coupon similar to above – generally of size: 12 in. wide, by 2 or 3 inches, in a neutral zone. A neutral zone is an area where the stresses are not too high, and preferably not too visible. Depending on the zone and the visibility, one can choose to replace the coupon where it came from. However, the decision to take one, four or twelve coupons on existing steel members is usually based on the structural engineer's confidence in the material and the apparent diversity of sources. One basic test will generally cost less than 500$ if the coupon is delivered to the testing company, and up to 1000$ if the company needs to go to the site, cut and bring back the coupon in the lab. A typical palette of tests includes a chemical test, and a mechanical test. The chemical test indicates the carbon, iron and silicon content, which will result in an "equivalent carbon" content, to evaluate the weldability of the steel. The mechanical test consists of both a traction test and an elongation test, to obtain both elastic and plastic limits of the steel.


How do demolition crews go about recovering steel?

It depends if the steel is to be cut into pieces for recycling or taken down to be reused elsewhere. Murray Demolition has the policy of leaving no steel behind. To extract steel members for reuse, Murray Demolition comments that there are basically two methods: unbolting or shearing. In the case of the ROM building, the beams reused were unbolted. Since the system was composite (i.e.: shear studs linked the concrete slab and the top flange of the steel beam), some supplementary cleaning was required. The beams were 38 ft long but the University of Toronto Student Centre only needed 32 ft spans. After the beams were shortened to the required length by the fabricator, they were installed. One should note that the depth of reused beams are likely going to be higher than what is needed, as one will generally recover members which are longer than required, since it is easier to shorten a steel member, than to lengthen it! The reason is that longer members need to be deeper than the shorter members, if the loading situation for each case is not too different. Shearing (using a giant metal scissor-like equipment) the member near the connection or support introduces residual stresses. Hence, the member is further cut back 2 or 3 feet in the fabricator shop using a more refined cutting equipment. Again, this will mean a shorter member and a deeper section for the given length. Murray Demolition says one major "reused steel" client are the shoring contractors who need piles for deep foundation caissons. Demolition crews find that the behaviour of steel buildings is more predictable than a similar concrete building whose behaviour under demolition is directly tributary to the behaviour of the exposed rebars. If you compare a 3 million Sq.Ft. steel building to a 3 million Sq.Ft. concrete building, the steel building will cost 0$/Sq.Ft. to demolish compared to 2-3$/Sq.Ft. for the concrete building. The reason is simple: most of the steel can be salvaged and becomes revenue, whereas there are usually mostly costs associated to disposing the concrete. If you ask a demolition specialist his advice on designing for rehabilitation the reply would be that today's designers rarely take into account removal or recovery at the onset of project design. Murray Demolition gave as an example, a heavy concrete staircase in a major shopping mall which had to be demolished – it seemed obvious to them that in such applications and building types where face-lifts seem to occur at the rate of one every ten years – that recoverable steel would have been a better, and much easier choice of material – in terms of ease of demolition, and resale value.


How is the recovery of steel addressed in the LEED™ Materials & Resources category?

In the Materials & Resources category, there are a total of seven types of credits – five of which can be applicable to steel.(2,3)

• Under Credit 1: Building Reuse (2 possible points) – 1 point is allocated if 75% of the building structure and shell (excluding windows) is preserved (add an additional point if 100% – along with 50% of the walls, floors, and ceilings). Steel structures can easily adapt to be modified and reinforced.
• Under Credit 2: Construction Waste Recycling (2 possible points) – 1 point is allocated if 50% of the waste is diverted (add an additional point if 75%). LEED™ recognizes both types of waste: demolition and ‘by-product’ of construction.
• Under Credit 3: Resource Reuse (2 possible points) – 1 point is allocated if 5% of the total building materials consist of salvaged or refurbished components – by cost (add an additional point if 10%).
• Under Credit 4: Recycled Content (2 possible points) – it is important to note that LEED™ – Version 2.1 offers two options for calculating recycled content: Option 1 – 1 point is allocated if 5% of the total value of materials for the project consists of post-consumer recycled content (add an additional point if 10%), and Option 2 – 1 point is allocated if 10% of the total value of materials for the project consists of a 2/1 ratio of post-consumer/post-industrial recycled content (add an additional point if 20%). Option 2 may be more suitable as today’s average recycled contents contain approximately 64% post-consumer steel and 30% post-industrial steel. In the United States, the American Iron and Steel Institute (AISI) requires its steel producers to provide a letter confirming the production process – to provide the LEED™ requirement for documentation on the origin of the percentages of steel used to create the components used in the project. The AISI web site (www.aisi.org) produces an example of such a letter. It is important to point out that a steel producer using a Basic Oxygen Furnace uses approximately 35% of existing steel to make new steel – compared to steel producer using an Electric Arc Furnace, where nearly 100% of existing steel is used. Clearly the producer’s letter should not only state the type of furnace used, but also trace the percentages between post-consumer and post-industrial steel.
• Under Credit 5: Local/Regional Materials (2 possible points) – 1 point is allocated if the place of steel fabrication (where steel is formed into its final shape) is within 500 miles of the project site (add an additional point if the raw materials for the production of that steel are extracted or harvested within 500 miles of the project site – for steel, this means the final location where the metal served its last useful purpose before becoming scrap), a quantification only possible if the producers start tracking the origins of the scrap they use and produce such information in a product documentation letter.

The future of steel recovery is very green, both in terms of recyclability and reuse. The industry catered to recycling has a strong history which can only continue to contribute to a future of possibilities. Although information needs to be more readily available, all signs indicate that improvements will continue given the many advantages, both economical and environmental, that recycling steel offers, particularly as it is an 'open loop' material. In terms of reuse, more work needs to be done, as at the moment, each search for reused steel requires a one-of-a-kind effort. We would like to suggest that structural engineers together with demolition companies and fabricators, can greatly contribute to the development of steel service centers' warehouse database for reused steel – which would offer links to available material, to the design and construction industry. Some warehouses could cater exclusively to used steel that has already been tested and whose dimensions are known. As we await such development, and in any case, involving structural engineers and fabricators early in the design process of a green building using steel makes sense, as they are more likely to have the knowledge of possible demolition sites or other sites (to be inventoried and explored for possible reuse) – an added contribution to a more integrated design approach, better LEED™ ratings, and consequently better green buildings.

References:

1. Climate VISION Initiative – Announcement. AISI, February 12th 2003. | www.aisc.org/sustainability
   
2. “Structural Steel Contributions: towards obtaining a LEED™ rating”. Modern Steel Construction, May 2003. | www.aisc.org/sustainability
   
3. LEED-NC Green Building Rating System™ Version 2.1), U.S. Green Building Council, November 2002 (revised March 14, 2003). | www.usgbc.org
   
4. SNF – Recycling is turning scrap into gold! – Brochure. | www.snf.ca
   
5. Fact Sheet "The Inherent Recycled Content of Today's Steel", Steel Recycling Institute, 2002 | www.recycle-steel.org/leed/2002Inherent.pdf
   
6. Recycling Scrapped Automobiles | www.recycle-steel.org/cars/autorec.html

For a longer list of references, please consult the CISC green steel resource page:
www.cisc-icca.ca/green