The works of the Paris 2024 Games at the forefront of the city of tomorrow

As part of the construction of the 70 Olympic structures, Solideo placed emphasis on the environmental requirements of the buildings. The public establishment claims a reduction in carbon footprint of 47% compared to a traditional project. It also leaves several technical and regulatory advances to the construction sector.

The legacy so vaunted by the promoters of the Paris 2024 Olympic and Paralympic Games (JOP) does not only concern the inhabitants of the territories where the 70 structures of the Olympic Works Delivery Company (Solideo) were built. Through its environmental requirements, the public establishment wanted to show that “the dense city still has a future in the 21st century”, according to Nicolas Ferrand, executive general director of Solideo.

“We can respond with today’s solutions to four major issues: the question of reducing the carbon footprint of our activity, that of climate change, the question of material savings and the question of biodiversity,” he says. Thus, Solideo pushed companies to propose and experiment with innovations. The Caisse des Dépôts, CDC habitat and Icade group thus built, in the Quinconces sector, a building called “Cycle” capable of achieving 60% savings in drinking water thanks to on-site wastewater treatment. Like 33 other projects, this building benefited from the Solideo innovation fund, endowed with 36 million euros.

Of the 18,000 m3 of concrete that Vinci construction had to pour in the Universeine sector,
12,000 m3 were used with an ultra-low-carbon cement-free product. © Dorine Bouteiller

To make its Olympic works and in particular the Athletes’ Village a “showcase”, Solideo indicates that it wanted to develop two types of innovations. First test “prototypes in real conditions”, in the words of Nicolas Ferrand, who takes the example of the “Cycle” building and recalls the failure of the printed concrete bridge stopped in 2022 because it “folded” . The institution has also focused on the generalization of more mature technologies: “Typically, the carbon issue in the Olympic Village has led us to make ultra-low-carbon concrete and wood with 17 Atex (technical assessment of experimentation, editor’s note ) of wood,” explains the general director of Solideo. After the official delivery of the Athletes’ Village on February 29, the public establishment estimates having reduced its carbon footprint by 47% compared to a traditional project. The performance of the operation is also based on the use of the heating network and surface geothermal energy developed with the support of Ademe to the tune of 2.7 million euros.

Use of wood

To achieve this, the use of wood as a construction material has been popular in several works, whether for floor surfaces or structures. Solideo thus established a partnership with the wood industry, which materialized in the creation in 2018 of the France Bois 2024 project to support the use of this low-carbon solution. The wood used on the Olympic works sites had to come 100% from eco-managed forests, certified PEFC or FSC, including 30% from French forests. It made it possible to create the facades and certain frameworks of the buildings of the Athletes’ Village. Solideo also highlights the fact that all housing buildings less than 28 m high “integrate wood into the structure”. Wood was also used on structures such as the Olympic Aquatic Center, next to the Stade de France.

In the Universeine sector of the Athletes’ Village, whose client is Vinci Immobilier, wood was combined with the use of a low, very low and ultra low-carbon concrete solution. “The whole challenge is the mix of low-carbon concrete and wood materials to reduce the carbon footprint of constructions,” explains Bruno Paul-Dauphin, director of Exegy low-carbon concrete solutions at Vinci construction. Among the techniques developed by Vinci construction, there was “an ultra-low-carbon solution without cement which left its mark because it completely transformed the concrete material”, he continues.

Low-carbon concrete from “laboratory to industrial solution”

Of the 18,000 m3 of concrete that Vinci construction had to pour in the Universeine sector, 12,000 m3 were poured with an ultra-low-carbon cement-free product and 6,000 m3 with low-carbon concrete based on blast furnace slag. . This innovation was partly financed by the fund set up by Solideo. “The Athletes’ Village allowed us to move from the experimentation carried out at Vinci headquarters to an industrial deployment on site of our ultra-low-carbon solutions,” indicates Bruno Paul-Dauphin.

Bruno Paul-Dauphin, director of Exegy low-carbon concrete solutions at Vinci construction. © Aurélie Coudière

Concretely, low-carbon and ultra-low-carbon concrete only represents between 70 and 90 kg of CO2 per m3, compared to 250 kg of CO2 for conventional concrete. The use of these innovations made it possible to save some 5,000 tonnes of CO2 equivalent at the Athletes’ Village. “The feedback is positive but these ultra-low-carbon solutions present an additional cost both in terms of materials and for implementation,” notes Bruno Paul-Dauphin. In the Athletes’ Village, for example, it was necessary to invent a system of heated gates to maintain a high temperature, as low-carbon concrete is less resistant to the cold. “To support the transformation towards low-carbon concrete, we must work on the material, adapt the methods in certain cases and possibly upgrade the equipment in cold weather,” underlines the director of low-carbon concrete solutions Exegy.

Vinci was able to renew the experience of ultra-low-carbon concrete on a housing project carried out by Immobilière 3F in La Celle-Saint-Cloud (Yvelines), with the pouring of 2,536 m3. For the company, the 2024 JOPs are support for pursuing its objective, by 2030, of using low-carbon concrete on 90% of its sites. “We did not wait for the Olympic Games to launch into low-carbon concrete but the Athletes’ Village confirmed that the direction taken in 2020 was the right one,” specifies Bruno Paul-Dauphin.

70% reuse of materials used

The Weber company, owned by the Saint-Gobain group, also had to comply with the requirements set by Solideo and develop products as part of the Games projects. “We have solutions that can be adapted to wood construction but they must also adapt to the low-carbon strategy, so we went with air lime coatings,” explained Jean-Claude Giraud, prescription marketing manager. at Weber, during a presentation of the Saint-Gobain group’s innovations in the Athletes’ Village on October 19, 2023.

The Olympic works also allowed the company from the same Placo group to stand out in terms of reuse, with the deployment of 60,000 m2 of removable and reusable partitions. “We were looking at the subject of re-employability in standby mode because we were working on the recovery of building waste in our research and development (R&D),” recalls Manel Ben Saad, director of prescription at Placo. In its specifications, Solideo imposed on developers a reuse rate of 70% of the materials used.

The use of wood as a construction material has been popular in several projects. © Solideo

Placo partitions are placed in the athletes’ accommodation to create separations between spaces, which will disappear in the legacy phase. These white partitions, fitted like a puzzle in the middle of the athletes’ apartments, are made up of already existing materials: frames, plasterboard or screws. “What changes is the assembly,” explains Manel Ben Saad. The major innovation is the fixing of the partition, because we no longer drill the floor and ceiling to ensure clean dismantling. »

The beginnings of reusable partitions

This reusable product is the culmination of a year of R&D but is part of a longer-term strategy of the company. “For us, it’s not a parenthesis,” maintains Manel Ben Saad, who explains that several project owners are now interested in this product. In October, most of the Athletes’ Village partitions will have to be redeployed on other sites. The question that will have to be resolved is also that of the insurability and performance of these reusable partitions. Manel Ben Saad draws a parallel with the use of recycled material in the design of certain materials. “20 years ago, we said to ourselves that it was impossible to certify its performance and yet, today, we can integrate more than 50% of recycled material into a plasterboard while guaranteeing performance,” explains -she.

Today, Placo is considering developing new reusable partitions, more aesthetic and “even better” eco-designed. “The JOP 2024 allowed us to go further,” enthuses the director of prescription, who congratulates an experience which “had the benefit of getting manufacturers moving, accelerating our internal processes and having shown what can be done.” The Olympic works and the objectives of Solideo have thus enabled companies in the construction sector to show their know-how to adapt to the standards of the city of 2050 and encourage the massification of these solutions.