Materials make the core of a building. They can make or break the conceptual ideology, philosophy, and aesthetics of a design. Architects have always preferred the use of mild steel and carbon steel in construction for their ability to transform building design into more than a grid structure and its sturdy nature through the properties of resistance.
But can we as designers transition to alternative materials as opposed to the typical methodologies of building construction? Weathering steel, also known as Corten steel is a sustainable alternative that can be considered a replacement for mild or carbon steel that is otherwise popularly chosen for the construction of buildings.
Weathering steel is a high-strength low alloy steel that comes from a family of low carbon steels with additional alloying elements mixed in with the carbon and iron atoms. It was originally developed by the United States in the 1930s and given the popular name of Cor-ten. Weathering steel was initially used only for outdoor applications, more commonly bridges because of its comparatively better strength and higher corrosion resistance than typical low carbon steel grades.
How does it work?
As low carbon steel, weathering steel typically has less than 0.3% carbon by weight that allows it to remain ductile and tough. The constitution of the material is composed of different alloying materials but the key three elements that raise its strength and render it corrosion resistant are nickel, copper, and chromium.
One of the main characteristics of weathering steel is the corrosion capacity it can endure making it environment-friendly as compared to other forms of steel. This material does not completely resist rust formation, but the material is developed to weather corrosion in a manner that keeps it limited to the outer surface instead of letting it spread inwards thus affecting the strength and durability of the structure.
Moisture and air are two components that lead all low alloy steels to form contaminants on the metal surface. As they age, the rust layer creates barriers to the ingress of oxygen and moisture, thus slowing down the rate of rusting. In suitable environments weathering steel forms a protective rust patina that slows down the corrosion rate to such an extent that outdoor structures such as bridges fabricated from unpainted weathering steel can achieve a lifespan of over 120 years.
First glimpses of weathering steel
A well-detailed weathering steel structure can withstand numerous changes in the course of its standing capacity. In the presence of appropriate environments, they provide an attractive, ideally low maintenance, economic and sustainable solution. This alternative material solution saw its first application in 1964 when it was used in the construction of the John Deere Headquarters in the United States by architect Eero Saarinen. By 1967, the use of this low alloy carbon steel increased and its presence existed in most outdoor citywide structures.
The first weathering steel footbridge was constructed in the UK in 1967, and thereafter Corten steel was used and preferred around the UK and Europe as a primary material for bridge construction. The use of Corten steel has since then spread worldwide and it remains the material of choice for bridge decks. Weathering steel remains a suggestive alternative material to other carbon steel elements or mild steel construction. The use of this material for building construction to date enlightens designers on the advantages and limitations and how it stands as an alternative material in construction.
John Deere Headquarters, Moline, Illinois, USA
Standing strong as the first project to incorporate the use of weathering steel in its construction, the John Deere Headquarters located in Illinois is a complex design of three buildings. According to specific instructions given by company president William Hewitt, the buildings were constructed in Corten steel to achieve a down-to-earth exterior facade. The material resisted corrosion and formed a protective coating of iron oxide that develops an earthy color as it matures.
The application of this material gave the building an earthy look as it oxidized and aged and with attributes like low maintenance and long-term performance standards, the building completed in 1964, continues to be the world headquarters for John Deere.
Barclay’s Center, New York, USA
The Barclays Center is a prime sports arena located in Brooklyn, New York, with a seating capacity of 19,000 individuals. The center was shaped with a responsibility to achieve balance with an exterior composed of 12,000 uniquely shaped panels in weathered steel that recall the color and scale of the adjacent brownstone blocks. The pioneering construction technology achieved with this iconic exterior presented an integrated and streamlined design with the facade panels emphasizing the contrast of light and dark.
The building’s facade, wrapped in alternating bands of weathering steel and glass corresponds to an output that portrays scaled intricacy of the curving metal latticework creating a rich and dynamically textured surface. The steel used is unique, as its rich patina reflects changes in the weather, and the use of the glass skin reflects the colors of its surrounding cityscape. Weathering steel has an aesthetic appeal that is not comparable to other building materials with cost benefits that followed a strict budgetary constraint during construction.
A few enigmatic examples also include the Leeds Broadcasting Tower in England, the Design Museum in Israel, and many more archetypal structures all over the world. With its benefits of cost, maintenance, speed of construction, and environment-friendly features, weathering steel has been recognized and can be used as an alternative material for construction.
Sustainability at its best
Weathering steel has its limitations when it comes to atmospheric conditions like damp, wet, or polluted surroundings, nevertheless, the material has merits that outweigh these, making it one of the most sustainable and environment-friendly materials of construction in the steel family. The outer layer of rust formed on surfaces allows the material to remain corrosion-resistant and structurally sturdy for a long time.
Painted or unpainted, weathering steel ensures a longer service life at minimum or even no maintenance work. When painted, it can double intervals between maintenance with a coat of paint. When we look at the material complexity, the purpose it serves, and the years it completes at a stretch, weathering steel proves to be an excellent alternative material for building construction.
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