Sprayed Ductal®: at the EDF Campus for the first time
Ductal®, supporting the loftiest architectural ambitions
“Using Ductal® can take architecture in many directions,” says Pascal Pinet, Business Engineer in charge of Ductal® Europe’s iconic projects. Some take a “high-performance” route by building large overhangs, a highly technical expression of the capabilities of Ductal®. Others focus on Ductal®’s ductile properties to sculpt prefabricated monolithic façades of sophisticated and meticulous contours, “skins” where the possibilities for large dimension elements seem limitless.
Ecdm chose to focus on the material’s intrinsic finesse, precision, plasticity and watertight properties for the EDF building in Plateau de Saclay, in addition to taking advantage of the material’s flexibility, contraction and traction capacities.
The specific advantages of sprayed Ductal® give architects greater freedom to design innovative buildings. Using this material, the EDF Campus has been conceived as a compact urban neighborhood, and is true architectural feat.
Compact architecture, for a modular and unified urban neighborhood
Unlike the traditional American campuses designed as parks punctuated by blocks of buildings, EDF wanted to build a single, multipurpose building, open 24/7 and comprising training centers, reception and meeting areas, living and relaxation spaces and, of course, dorm rooms. With this in mind, the architects at ecdm imagined an ambitious project. “Using farmland to build buildings is no longer in step with the times,” says Emmanuel Combarel and Dominique Marrec, the agency’s founders. Using a contemporary approach that took into account the stakes tied to land use, ecdm turned the concept of an inhabited urban campus on its head. The agency organized the campus around a central courtyard, with glass viewing points throughout the 360° shaped campus that showcase the surroundings. In this way, the campus integrates and highlights the landscape.
A layered façade in Ductal®
The building concept uses distinct levels. “Everything is organized to create a campus that is easily understandable and navigable for people who need to quickly find their way around,” the architects say. For this reason, the hall, exhibition space and training areas are located on the three lower levels, while the private living quarters are located on the two upper levels, with dining spaces and areas for socializing or relaxation placed in between.
The division of the façade into three distinct layers of Ductal® and glass give the building a unique visual identity.
From the ground level to the third floor, prefabricated shells of sprayed, dark-brown tinted Ductal® highlight the structure of the building. These large shells offer a seamless visual appearance along the bottom layer, while optimizing use of material. A bicomponent stain in a 75% transparent brown hue reveals the extreme finesse of the UHPC mesh.
On the fourth floor, a partially reflective wall surrounds the dining and relaxation areas, which remain open to the landscape.
The building’s two upper levels appear to levitate above this partition. In the living quarters, large prefabricated shells of sprayed Ductal® encompass each of the 270 rooms in pairs, covering the blinds and exterior joints. A 25%-transparent gray stain caps off the crown of the concrete.
Given the capacity of sprayed Ductal® to meet the objectives of the EDF Campus façade, architects can now research new ways to use prefabrication techniques.
Spraying: the product of 15 years of research
Using sprayed UHPC is the result of 15 years of research into the use of Ductal® by LafargeHolcim and ecdm. This research also led to the construction of a Bus Center for RATP in Thiais outside of Paris, and the Budin daycare center in Paris.
The efforts led to an innovative prefabrication technique. Until now, Ductal® concrete had been poured to create façades. But this time, Ductal® concrete was sprayed into wood or elastomer molds. To do this, the formula for the cement matrix had to adapt to the spraying technique. The prefabrication process was developed in Lyon, at the LafargeHolcim Central Research Laboratory, the biggest R&D center in the industry. There, a special Ductal® team works continuously to develop new formulas for ever more innovative applications. For the spraying technique, the team focused on several challenges. “We had to thin out the formula to allow the material to flow through the spraying mechanism, including pump, pipe and nozzle, before it is sprayed as a mist of fine droplets. We also had to make sure the concrete would stick to the sides of prefabricated pieces, vertical walls measuring 60 cm,” explains Pascal Pinet.
This procedure, which makes it possible to produce ultrathin shells, shows the ductile qualities of UHPC. “The resilience and the capacity of the set concrete to deform and return to its original state made it possible to produce large single block elements,” says Pascal Pinet.
Spraying eliminates the need for backing molds. “It becomes possible to spray Ductal onto more complex shapes, which is difficult to accomplish without backing molds,” Pascal Pinet explains. “For even more complex projects, the procedure is much less costly because the pressure of sprayed material is less than its self-compacting equivalent. Molds and backing molds can be less resistant and impermeable than those used with traditional pouring methods; and can be made with cost-effective materials. In the field of UHPC, only Ductal® can be sprayed. This technique made the project possible.”
A multitude of benefits
Ductal® is a material known and appreciated by architects for its many properties including its resistance, ductility, durability, aesthetics, precision, low porousness, etc. Used for the first time at the EDF training center in Saclay, the spraying process expands on these advantages.
In Saclay, the façade elements in Ductal® form a seamless concrete skin. The Ductal® panels measure up to 8 meters in height, 2.70 meters in width and 60 centimeters in depth—all with a thickness reduced to 15 millimeters along the middle of the material.
The large panels give an appearance of astonishing uniqueness. “The façade shows only the meeting of glass and concrete,” conclude the architects. That is ample cause for satisfaction among the Ductal® teams. “Creating forms that have never been seen before is the reason we come to work,” says Pascal Pinet.
26.000 sqm floor surface
12.000 sqm façade, of which 4.000 sqm in
15.000 employees trained each year
70 training rooms
2 big modular rooms
One plenary hall
One 450 sqm show room
270 individual bedrooms
One 300 seat restaurant and 4 private lounges
One lounge bar
One fitness room
One rest room
One media library
One technical training hall of 3.000 sqm
One 450 space parking
One big garden
One outdoor electric poles pedagogical space
Sprayed Ductal® panels
Height: 8 m
Witdth: 2,70 m
Depth: 60 cm
Thickness: 15 mm
Delegated contracting client: Sofilo
Design assistance: Orénoque
Construction assistance: AIA Associates
Structural engineering consultant: JPM COFER
Façade engineering consultant: VP&Green Engineering
UHPC façade elements: Ductal®, LafargeHolcim/Betsinor/C&E Engineering
Certifications: HQE Excellent and Breeam Excellent
EDF Campus: winner of the Duo@work architecture prize
These innovations have earned praise. For the EDF Campus in Saclay, ecdm and LafargeHolcim took home the Duo@work first prize, an architecture contest recognizing projects combining architectural research and innovative industrial design. For the occasion, architect Dominique Marrec praised all the aesthetic and technical potential of the material, calling it “a new generation of UHPC that offers greater freedom in terms of the prefabrication process.”
Pascal Pinet reiterated that same industrial and architectural harmony, saying “The relationship between Ductal® and ecdm enabled us to evolve and innovate. For 15 years, we have worked together in continuous collaboration, with each project laying the basis for the next.”
In addition to the EDF Campus, other projects are also underway. The La Marseillaise tower is one noteworthy example, a skyscraper rising from the coast of Marseille, designed with architect Jean Nouvel. This project could soon push the envelope of the possibilities offered by Ductal®. “We went even further by adding exterior walkways intended for maintenance, designed as an integral part of the Ductal® façade… Just wait until you see it!" beams Pascal Pinet.
They talk about it...
In short: the benefits of sprayed Ductal®
Alongside the “traditional” properties of resistance, ductility, durability, aesthetics, precision, low porousness and impermeability of poured UHPC, sprayed Ductal® gives:
- a smoother aspect and texture,
- the thin finesse of large scale single block elements,
- extraordinary precision, eliminating the need for adjustments on the worksite and enabling regular joints with increased finesse,
- ability to produce complex architectural forms with greater ease,
- economies of scale with molds,
- and high-performance thermal insulation.