Concrete has long been the backbone of modern infrastructure, but its limitations—brittleness, high carbon footprint, and labor-intensive reinforcement—have driven innovation. Enter Steel Fiber Reinforced Concrete (SFRC), a revolutionary material that’s transforming tunnel construction by combining strength, sustainability, and efficiency.

The carbon-saving revolution in tunnel linings

With urban spaces expanding underground to accommodate transit networks, utilities, and more, sustainable construction methods are critical. Traditional tunnel linings rely on steel rebar and thick concrete layers, contributing to 70% of a tunnel’s embodied carbon. However, Permanent Sprayed Concrete Lining (PSCL) reinforced with high-performance steel fibers like Dramix® is changing the game.

Key advantages of SFRC in tunnels:

50% less steel and concrete compared to rebar-reinforced linings.
Up to 75% lower CO₂ emissions by reducing material use and optimizing designs.
Thinner, stronger linings that maintain durability over a 100-year lifespan.

How steel fibers reinforce tunnel construction

Unlike conventional rebar, steel fibers are mixed directly into concrete, creating a 3D reinforcement network that:

Bridges cracks under stress, improving flexural strength.
Simplifies construction by eliminating rebar placement and formwork.
Enables sprayed concrete techniques, speeding up tunneling projects.

Project spotlight: West Connex M4-M5 Link Tunnels, Sydney

27,000 m³ less concrete (15% reduction in thickness).
830 tonnes fewer steel fibers (10% reduction).
33,000 tonnes of CO₂ saved—equivalent to removing 9,000 truck trips.

©West Connex M4-M5 Link Tunnels

The science behind high-performance fibers

Not all fibers are equal. Dramix® 4D end-hooked fibers, for example, deliver:

Higher residual strength (fR4k = 3.0 MPa) for load-bearing durability.
Optimal dosage rates (35–40 kg/m³) to prevent balling and ensure even distribution.
Certified sustainability with EPD-backed low-carbon production.

A global shift to sustainable tunneling

From Montreal’s REM Metro (featuring North America’s deepest station) to London’s Crossrail, PSCL is proving its worth:

Faster construction: No rebar installation or formwork delays.
Longer service life: 125-year designs for critical infrastructure.
Regulatory momentum: Standards like fib Model Code 2010 now support FRC-based designs.

©Edouard Montpetit (EMP) station. Photo credit: AECOM

The new frontier in tunnelling

The future of tunneling lies in low-carbon, high-performance materials. Innovations like recycled steel fibers, advanced binders, and thinner linings will push sustainability further. As cities dig deeper, SFRC ensures they do so stronger, smarter, and greener.

Ready to build the future? Explore with us how SFRC can elevate your next project.