Green Rebar - The Environmental Advantages of GFRP Reinforcement (over steel)
The Environmental Advantages of GFRP Reinforcement (over Steel)
The steel industry is one of the largest producers of carbon in the world. Every tonne of steel produced emits approximately 1.83 tonnes of carbon dioxide, equating to around 7-8% of global emissions. It is estimated that around half of all steel produced goes to the construction industry and 44% of construction’s steel consumption is used for reinforcement. This equates to a whopping 1.5% of global carbon emissions attributable to steel rebar alone. In addition, concrete spalling caused by steel reinforcement corrosion is a significant issue that often leads to structural deterioration and the premature end of service life of structures. In the US alone, corrosion of both steel and reinforced concrete infrastructure costs the economy an estimated US$22 billion each year.
The costs, emissions and waste associated with the maintenance, repair, demolition and replacement of structures further adds to the impact of steel-reinforced concrete on the environment. This presents an opportunity for decarbonisation of the industry through the use of more environmentally-friendly alternatives in lieu of steel reinforcement such as glass fibre reinforced polymer (GFRP).
Environmental Benefits of GFRP in Production
With advancements in material technology, steel alternatives such as GFRP can now provide sufficient structural performance for reinforcing concrete at comparable or lower cost than steel, according to a study by University of South Australia.
Another study, undertaken by the Malaviya National Institute of Technology, comparing the use of steel rebar with non-metal alternatives including GFRP show that GFRP produces far fewer emissions compared to steel per tonne produced. Furthermore, the study took into consideration the design capacity of the reinforcement and allowed for the actual volume of material needed for a real project. The results of the study show GFRP reinforced beams produce 43% less CO2 emissions compared with steel and reduce energy consumption by almost half (see Figure 1).
Figure 1: Parametric study results plot of emissions and energy consumption of steel rebar vs. non-metallic rebar alternatives. Source: ENVIRONMENTAL AND ECONOMIC COMPARISON OF FRP REINFORCEMENTS AND STEEL REINFORCEMENTS IN CONCRETE BEAMS BASED ON DESIGN STRENGTH PARAMETER by N Garg & S Shrivastava, (Malaviya National Institute of Technology (MNIT), Jaipur, India & Govt. Engineering College, Bikaner, India) https://ukiericoncretecongress.com/Home/files/Proceedings/pdf/UCC-2019-1051.pdf
Apart from emissions, GFRP also has benefits on the consumption of natural resources. Early studies show GFRP could allow the production of concrete using seawater, sea sand and sea aggregates, avoiding the consumption of scarce resources such as fresh water, river sand and crushed rocks. Seawater concrete has additional benefits such as lower cement content, less transportation and the ability to reuse the concrete’s constituents at the end of the structure’s life in new seawater concrete.
Environmental Benefits of GFRP in Transportation
Road freight is responsible for approximately 5% of total global carbon emissions, with construction freight representing around 12% of the total freight volume. This is another sector with the potential for substantial decarbonisation through more efficient construction practices and smarter materials selection. Steel weighs around 7,850 kg/m3; over 3 times that of concrete. Consequently, the weight of steel limits the volume of reinforcement that can be carried by a single truck.
GFRP is one quarter of the weight of steel, making transport more efficient by substantially increasing the volume of reinforcement that can be carried by a single truck. This could save several hundred or even thousand freight kilometres per project.
Environmental Benefits of GFRP in Service
Reinforced concrete used for infrastructure is designed to have a 100-year lifespan. For buildings, this is only 50 years. In reality, reinforced concrete structures often start to deteriorate much sooner, in as little as 10-20 years.
Poor quality control during construction can often undermine the design life of a structure due to factors such as insufficient cover depth on the steel reinforcing or cracking in the concrete beyond expected tolerances. These can expose the steel reinforcing to premature corrosion, substantially reducing the overall service life of the structure. The new concrete needed to repair and replace prematurely deteriorated buildings and infrastructure is estimated to cost trillions of dollars in the US alone and contribute significantly to both carbon emissions and waste.
The use of a non-corrosive reinforcing alternative such as GFRP, eliminates the biggest vulnerability of reinforced concrete: corrosion-induced concrete spalling; thereby improving the durability of reinforced concrete by a significant magnitude. This includes a substantial reduction in the need for repairs during the structure’s design life. Enhanced durability of our structures avoids the emissions and waste associated with 3 critical stages of a structure’s lifecycle: maintenance, demolition and replacement. Ultimately, this enhanced durability is needed to address both environmental challenges of climate change and waste.
As nations around the globe strive towards net zero, steel alternatives will represent an essential component of sufficiently decarbonising the construction industry. This is due to both a carbon-intensive mining and production process of steel as well as its vulnerability to corrosion which, consequently, causes premature deterioration of structures. A renewed and improved focus on the durability of structures beyond 50-year and 100-year lifespans is critical to the reduction of emissions and waste and ultimately preservation of our natural environment.