SUSTAINABILITY & CIRCULAR ECONOMY | INSIGHT


that also contains conventional steel reinforcement. The conference paper presents various scenarios and illustrates their impact on the sustainability performance of tunnel linings. The combination of innovative binder and


reinforcement concepts offers great potential for the realisation of sustainable and robust bored tunnel linings. The following conclusion has been presented in based on testing realised with Dramix®


fib congress7


4D 80/60BGP: ● Deflection hardening: The tested SFR AAC shows a substantial deflection-hardening and post-cracking flexural tensile strength. The observed COV for the test data lies within reported results for beam bending tests of traditional SFR concrete;


● Structural feasibility: The presented results show that it is possible to produce a structural feasible Portland cement-free concrete in regard to three- point beam bending tests. It is expected that a sufficient steel fibre class in accordance with EC2/fib MC is achievable. This enables the use in structural applications.


● Impact of mixing sequence on fibre distribution: The mixing sequence had a strong impact on the fibre distribution for the used fibres and mix design. Adding the activator solution after fibre addition led to a clear improvement of the fibre distribution. A significant impact on other measured properties was not observed.


As has been stated, literature suggests a better


bond behaviour between AAC and steel fibres in comparison to Portland cement systems. Future research aims to investigate this for the presented mix design with high content of low-kaolinitic clay. Indeed, the total mass of CO2eq is what we want


to minimise from environmental product declaration and by decreasing the total mass of material. An Environmental Product Declaration (EPD) is a


document that transparently communicates the key environmental performance indicators of a product over its lifetime. A third-party verification ensures that data relating to environmental aspects of Dramix®


has been


validated by an external organisation. This declaration is the Type III Environmental


Product Declaration (EPD) based on EN 15804:2012+A1 and verified according to ISO 14025 by an external auditor. It contains the information on the impacts of the declared construction materials on the environment. Their aspects were verified by the independent body according to ISO 14025. Basically, a comparison or evaluation of EPD data is possible only if all the compared data were created according to EN 15804:2012+A1. The environmental impact of Dramix®


product


(cradle to gate with options) is largely dependent on the energy intensive production of steel (half product) on which the manufacturer has only a limited influence.


Traditional Reinforcement


0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0


Copenhagen Metro


Steel fibres


OPC Tons CO2 11% 44% 61% 72% 82%


OPC + supp AAM eq. per m3 Concrete


Westernscheide Green Heart Tunnel


STEP


Abu Hamour Doha Metro AAM Azenario AMM case


The carbon impact of steel production (Wire Rods)


in the product stage A1 is as high as 85%. The impact of the production line largely depends on the amount of electricity consumed by manufacturing plant (0.34 kWh/kg of product). There are no significant emissions or environmental impacts in the A3 production processes alone (partly gas combustion). The production process itself does not have significant environmental impacts in the life cycle. The use of steel fibre reinforced concrete will help


to meet the aims of producing low carbon lining by concrete consumption and steel reinforcement saving, respectively. If ductility and durability have been the key words the last 40 years, then sustainability will be the key driver for further FRC lining development in the coming years. In the meantime the new level of quality control


from product specification, FRC testing , introduction device and non-destructive method provide additional peace of mind. We all believe that tunnels should use smart and


sustainable construction materials. The future of tunnelling is choosing these materials today.


REFERENCES ● 1


● 2 ● 3 Above:


Carbon performance evolution across time for tunnel projects PHOTO CREDITS: COWI


FIB (2010) Model Code 2010 – First complete Draft. Bulletin 55-56.


(2017) ‘Precast tunnel segments in fibre reinforced concrete’ fib bulletin 83.


EN 14651 (2005) ‘Test Method for metallic fibre concrete. Measuring the flexural tensile strength’.


● 4‘A leap forward for SFRC segmental linings in France’. Tunnel Tech (2022).


● 5


‘Sustainable Tunnel Linings Using Innovative Binders and Steel Fibre Reinforcement: Practical Experience and Research Findings on CO2 Reduction’. STUVA 2025, Hamburg


● 6


‘Advancing Sustainable mobility; design and construction innovation in Lot 1 of the Fortezza Ponte Gardena section of the new Brenner Railway’. Gallerie E Grandi Sotterane, N155 September 2025.


● 7


Glissner, M. & Edvardsen, C (2025) ‘Portland cement-free steel fibre reinforced concrete for structural tunnel applications’. Technical University of Denmark & Cowi.


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