We officially launched our new STEM Spotlight Luxembourg webinar series on Monday, 29 June. The inaugural speaker was Prof. Numa Bertola, Assistant Professor at the University of Luxembourg, who delivered a presentation entitled « Sustainable Maintenance of Concrete Structures. »
Before handing over to the speaker, Anne-Marie Solvi, Vice-President of the Association of Engineers and Scientists in Luxembourg, introduced the STEM Spotlight concept, a new webinar series organised by our association. Its objective is to offer regular, accessible presentations on scientific and technical topics in order to spark interest in STEM among a broad audience.
Our members are encouraged to suggest topics they would like to see covered or even volunteer as speakers to share their own expertise. While this first webinar was held during the lunchtime break, other time slots may also be considered for future editions.
From Singapore to Luxembourg
Now an Assistant Professor at the University of Luxembourg, Numa Bertola is a civil engineer by training. He studied at EPFL (École polytechnique fédérale de Lausanne) before completing his PhD at the Singapore-ETH Centre, the research centre established by ETH Zurich in Singapore. He then returned to EPFL for a postdoctoral fellowship before joining the University of Luxembourg, where he now leads a research group dedicated to the sustainable maintenance of concrete structures.
Keeping existing structures
Concrete is responsible for around 10% of global CO₂ emissions, with cement production alone accounting for approximately 8%. As the built environment generates around 40% of global CO₂ emissions, resource consumption and construction waste, reducing the environmental impact of existing infrastructure has become a major challenge.
Prof. Numa Bertola explains that extending the lifespan of existing structures is one of the most effective ways to improve sustainability. Since 99% of the buildings and infrastructure that will exist next year already exist today, preserving and upgrading existing assets can significantly reduce the need for new construction and the associated consumption of materials and energy.
The presentation focused on three complementary research directions developed at the University of Luxembourg.
Smarter maintenance through sensors and data
The first approach uses advanced sensing technologies and data analysis to better understand how structures actually behave. Rather than relying solely on conservative design assumptions, engineers can monitor bridges and buildings using distributed fibre-optic sensors capable of detecting extremely small deformations and crack openings.
Combined with data science and physics-informed artificial intelligence, these measurements allow engineers to detect damage at an early stage, optimise maintenance planning and, in many cases, demonstrate that structures are performing better than expected, allowing their service life to be safely extended.
The research team is also developing innovative colour-changing coatings that visually indicate the formation and growth of cracks, providing inspectors with a simple way to identify structural damage.
Extending bridge life with Ultra-High Performance Concrete
The second research area focuses on Ultra-High Performance Concrete (UHPC), an advanced material that is several times stronger and more durable than conventional concrete.
By applying a thin UHPC layer to existing bridges, engineers can both strengthen the structure and protect it from water infiltration and reinforcement corrosion. Experience in Switzerland, where more than 500 bridge rehabilitation projects have already been completed using UHPC, shows that this solution is often four times less expensive than replacing a bridge while reducing CO₂ emissions by approximately 80%.
A nationwide Swiss study suggested that strengthening bridges instead of replacing them could save around €10 billion and 2.5 million tonnes of CO₂ over the coming decades.
Reusing structural concrete instead of recycling it
The third research topic explores a more circular approach to construction. Instead of demolishing buildings and crushing concrete into recycled aggregates, Prof. Bertola proposes reusing entire structural elements such as floor slabs and beams.
Many buildings are demolished not because they are structurally unsound but because they no longer meet current functional needs. Their structural components often remain in excellent condition and could therefore serve in new buildings.
Experimental projects have demonstrated that reusing concrete elements can reduce the environmental impact of new construction by 80 to 95%, while maintaining the same structural safety and user comfort as conventional buildings. The main scientific challenge now is developing reliable methods to assess the long-term performance and safety of reused structural components.
A new approach to infrastructure management
Prof. Bertola concluded that future infrastructure management should combine continuous monitoring, targeted strengthening and the reuse of structural components. Together, these strategies can considerably extend the lifespan of existing structures, reduce waste and carbon emissions, preserve natural resources and lower construction costs.
Rather than viewing ageing infrastructure as a liability, the research demonstrates that existing buildings and bridges can become valuable assets in the transition towards a more sustainable and circular construction industry.
