Sustainable Solution for Sprayed Concrete in Underground Tunnel Projects

The tunnelling industry is at a tipping point where sustainability and decarbonization are at the top of executives’ agendas. To achieve a 1.5°C climate-change target by 2050, the tunnelling industry will need to reduce direct CO2 emissions to net zero.


Currently, too few countries and infrastructure projects are “walking the talk” and taking the initiative to reduce carbon. Perhaps, Norway is one country leading the way, and, as with their domestic electric vehicle market, electric drive construction equipment is being increasingly employed, with major cities to have carbon neutral construction by 2025.

The tunnelling industry is a contributor to global CO2 emissions and has a role to play in carbon reduction. The industry is facing increasing pressure from policy makers, investors, and customers to decarbonize operations. Figure 1 shows the approach to tackling carbon at an early stage.

Whilst some believe that low carbon tunnelling equates to higher project costs, currently, the best practices in carbon management in the construction industry suggest otherwise. Via a holistic approach throughout a project’s lifetime, with engineers focused on carbon saving, this intrinsically delivers an overall project cost saving too! This is certainly the ethos behind the standard PAS2080 of Carbon Management in Infrastructure and is well worth employing on projects for those keen on decarbonization.

Given this growing ambition and need for decarbonization, the three key aspects that would accelerate decarbonation efforts are: build clever, build efficiently, and build for a lifetime.

Build Clever: Start with innovative and considerate design

The biggest decarbonisation gains in tunnels come from decisions at the planning and design stages. In the design stage, the key differences are made, and in tunnels it is the design where the largest proportion of savings in carbon can be made. The modern sprayed concrete systems available today, combine high levels of Portland Cement replacement, polymer fibres, and innovative waterproofing technologies, offering possibilities to achieve over 50% reduction in carbon in tunnel linings. But again, these ‘Build Clever’ solutions must be captured and implemented at the early design stage to maximise carbon savings.

Build Efficiently: Smart equipment, people, and digitalisation

An example of sustainable offering is the SmartDrive battery electric vehicles that provide improved performance with zero local emissions. They also eliminate fuel and fuel transportation costs and have lower equipment maintenance costs. Norwegian tunnel contractors are already operating towards 2050 carbon net zero targets by using SmartDrive Spraymec 8100 SD spraying robots which are charged using hydropower grid electricity.

Virtual reality training platforms for key operators are becoming established in our industry and Normet’s VR Sprayed Concrete Simulator, endorsed by the international EFNARC C2 certification scheme, is the latest example allowing nozzle operators to hone their skills in the classroom environment. These simulators encourage safe and sustainable ways of spraying, and highlight areas for improvement, contributing to the trainees developing the right attitude and practice needed in underground spaces.

Figure 2 defines a holistic approach to tunnel design and construction to decarbonise the industry combining the build clever and build efficiently appraches.

Build for a Lifetime: Recycled materials for new equipment

We need to be less of a throwaway society, even in our tunnelling life. Normet builds equipment to last, and wherever possible, it recycles and re-purposes components and materials to build new equipment and new construction materials.

Finally, let’s promote the use of low carbon sprayed concrete technologies to build more sustainable infrastructure and support a better life for our current and future societies. High societal value is already measurable with the re-invigorated interest in underground green energy storage schemes, such as pumped hydro and prospective hydrogen storage, but also low project cost tunnel solutions to permanently connect our remote communities.

In a nutshell, multiple efforts on various fronts are needed to accelerate decarbonation efforts. It’s not just about low carbon concrete. We’ve all got some work to do, so let’s get to it and have fit “low-carb” tunnels.