A "concrete solution" for the building industry's ecological transition

Every building specialist knows the strengths and weaknesses of concrete. Since ancient Greece, mankind has been building its foundations, literally and figuratively, using concrete. So, yes, there were different mixes, notably lime- or clay-based, but the principle was the same: build strong, resistant structures. Modern concrete is advantageous because it resists very well to a force that compresses it: it won't break. This is less true when subjected to tension or bending. Concrete doesn't deform or bend, it just breaks.

Systems and processes were invented to strengthen the structure and make it more resistant to movement. For example, there's the rebar you often see on a building site, hundreds and hundreds of meters of steel that stabilizes and strengthens the concrete structure. Then there's the welded mesh, again made of steel, which is inserted into the concrete. The concrete forms a sort of waffle mould around these meshes. This is where the situation is no longer ideal. True, the concrete is strengthened and becomes able to withstand material tension, but over time the meshes and bars lose their ability to withstand cracks, and deterioration can occur. Bekaert, a partner of the Solar Impulse Foundation, has certified the Dramix solution, which involves integrating steel fibers directly into the concrete design. These fibers, which look like fine, elongated staples, are present by the thousands in a block and consolidate it, creating many more points of resistance than traditional solutions. So, when concrete comes under stress and cracks, the fibers will restrict the impact of the crack as much as possible, thus prolonging the life of the concrete and the construction itself. They don't prevent cracking, they don't make the material harder but more resistant, keeping it compact and healthy for much longer.

Dramix is also much more environmentally friendly. As the fibers are arranged homogeneously, the contractor needs less material for his concrete, reducing CO2 emissions by up to 35%. This optimization also means that less concrete is used during construction, as the slabs are thinner, reducing steel consumption (by up to 50%!) and water consumption (5.5% per cm less concrete). All this while increasing durability by 25%, which of course reduces operating and maintenance costs, again by up to -50%. This is the choice made by Grand Paris, which is building around 4km of the new Paris metro using this system.

I often talk to you here about new, emerging solutions that are looking to establish themselves in their sector. Steel fibers have been around for over 40 years, and Bekaert aims to produce over 323M tonnes by 2027. So it's an established, cost-effective, logical and simply more efficient solution. But the construction world remains conservative, sticking to what has 'always worked well'. It's not new, nor is it unique, but we need to take time to explain the benefits, present them and, above all, change mindsets. It's the only way to build...better.

*This article is taken from Les Echos/Investir, where Bertrand Piccard writes a monthly column*.