Reusing steel can make a critical difference in reducing embodied carbon, as steel can be manufactured entirely from recycled scrap/ secondary steel or from a mix of recycled scrap and new steel.
Steel is ideal for structures requiring high load-bearing capacity and large spans, due to its significant strength-to-weight ratio, while its strong tension and compression characteristics allow forversatile designs such as curved or irregular shapes.
Used in compact-cross sections, steel weighs about 60 percent less than concrete, and is eight times stronger in terms of tension and shear strength.
It can also be cost-effective for construction projects, as steel framing can be prefabricated off-site and help reduce project timelines, as well as reducing labour costs due to steel frames being erected quickly and easily.
Being a lightweight material, steel also facilitates easier transportation and assembly, further benefitting projects with tight schedules.
A study published last year highlighted five key challenges in reusing structural steel: limited material availability, maximising different reusable materials from demolition, lack of adequate design rules and standards, high upfront costs, andthe need to engage and coordinate the complete construction ecosystem.
The authors noted that the reuse of load-bearing structures was critical due to the significant contribution of these elements to the environmental impact of buildings, considering their substantial material mass and energy-intensive fabrication process.
According to lifecycle assessment case studies, a building’s environmental impact can be reduced by up to 63 per cent when its structure reuses steel elements, compared to weight- optimised solutions made from new material.
The authors said: “Since the material arising from demolished building stock only offers a reduced yield (about 30 per cent of material is lost as it is unsuited to reuse or damaged), the reuse market will permanently be restricted to the available materials.
“That being said, by using material efficiently, updating the standards and regulations, and increasing lifecycle thinking, the construction industry can and will save huge tonnages of carbon through steel reuse.”
While comprising about 9 per cent of GDP, Australia’s construction industry represents more than 18 per cent of all carbon dioxide emissions, while steel and concrete foundations make up a quarter of Australian emissions.
With circular economy approaches integrated into its operations, it is estimated the Australian construction industry could reduce carbon emissions by 165 million tonnes each year by 2040.
A number of factors are driving up the demand for recycled building materials, including higher materials costs, increasing number of construction projects, high government recycling targets, and consumer pressure for more sustainable products and practices.
The cost of conventional construction materials in Australia has been increasing for several years, while consumer surveys show nine out of 10 Australians are more likely to prefer ethical or sustainable products.
Using recycled or reclaimed building materials in construction often has lower cost than virgin materials, and allows for the implementation of a circular economy approach to construction, which minimises waste, energy use, and carbon emissions.
A recent report by the Australian Housing and Urban Research Institute (AHURI), undertaken for AHURI by researchers from RMIT University and the University of Wollongong, found there were deep institutional barriers to recycling and reusing construction waste.
RMIT’s Professor Tony Dalton said that although much of the waste generated through construction or demolition could be recycled or used as a resource in other ways, construction businesses in general were reluctant to do so.
He added: “Instead, they find that the cost of reusing materials is higher than using new materials; there isn’t an established market for waste materials; they’re hesitant to use available technological and practical knowledge to reduce
the waste; and there is a broad perception that Australia has abundant supplies of natural resources so they don’t really need to bother.
“We found that policy development should focus on creating incentives for construction companies to reuse materials, as well as encouraging other ways to reduce embodied energy through material selection and the use of local products that require less transportation.
“Government regulation can target low carbon building methods and materials, including supporting reuse, rethink, repurpose, or remanufacture.”
COLD-FORMED STEEL A SUSTAINABLE FRAMING MATERIAL
Steel framing produced with cold-formed steel (CFS) is a durable and environmentally friendly construction material that is increasingly becoming popular for both residential and commercial construction projects.
Notably, steel framing and in particular CFS is commonly comprised of recycled steel and leaves minimal impact on sites where it is used.
While many construction materials can only be downcycled into a lower-quality product, steel can be continually recycled and remade without any loss in quality.
A 2022 article published in Buildings posited that CFS was considered the most sustainable and increasingly popularmodern building product in the construction industry, and was mainly used in the commercial sector where entire buildings were constructed.
The authors said: “CFS is necessary for the modern construction industry, which requires maximum safety and strength embedded in a supporting structure.
“It is very beneficial for achieving thermal performance of nearly-zero-energy buildings because it can be easily combined with other components as the main structural system.”
CFS, also known as light gauge steel, has common construction applications including framing for buildings, roof trusses, flooring systems, and bridges, while also bringing several advantages to construction projects, including its strength, cost-effectiveness, versatility, speed of construction, safety and fire-resistance, and sustainability.
For these reasons, CFS is increasingly being used in Australian housing construction, particularly as framing for residential buildings, as steel framing members are lightweight, easy to handle, and are fabricated into desired shapes and sizes and assembled onsite.
Structural steel components are more durable and lighter than those of weight-bearing wood or concrete, with typical weight-bearing steel fabrication being 30 to 50 per cent lighter than its hardwood equivalent.
Due to its structural strength allowing greater innovation, steel framing enables architects to produce designs that are difficult to achieve with other materials, such as longer spans for open-plan living and homes on unusually shaped blocks of land and sloping sites.Moreover, steel framed buildings are safer due to their resistance to explosions, collisions, and fire.
This is achieved by substantially reducing the amount of flammable material used, making it an ideal choice for buildings in bushfire-prone areas – steel frames are already used in high-safety structures such as schools and aged care facilities.
