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Towards a “sustainable” concrete?

To support its research and development policy on carbon-free concrete, the Holcim cement group offers a range of innovative solutions for today’s and tomorrow’s buildings. From design and intelligent systems that rethink the building of structures (Striatus Bridge), floors (Rippmann Floor System) to green roofing, when it is not the construction of the house itself in 3D!

Sustainable development and energy saving issues are confronting the major construction groups with major new challenges. This is particularly true of the cement group Holcim, the world leader in construction materials and solutions (particularly since its merger with the French company Lafarge), which has embarked on a global strategy of innovative projects aimed at decarbonizing concrete, both in its production (green construction solutions, recycling principles) and in the development of a new generation of technologies. “We build the equivalent of a New York City every day,” says Edelio Bermejo, director of Holcim’s R&D department. “And 60 percent of the urban development needed to house the future population is still to come. So we have a huge need for concrete, and for that supply to be consistent, that concrete has to be increasingly sustainable.”

What is “sustainable” concrete?

In concrete terms, a “sustainable” concrete is first and foremost a concrete that is more focused on the local products, stones and aggregates, that are used in its composition, for understandable reasons of short circuits. Research on new compositions and manufacturing processes carried out in Holcim’s R&D department in Lyon, in partnership with an innovative ecosystem of start-ups and leading schools (MIT, Ecole des Ponts, Paris Tech), and through the sustainable concrete and cement ranges ECOPact and ECOPlanet, is another option. It allows the creation of constructions with concrete that is less CO2 and with a carbon footprint reduced by 30 to 100% (as is the case for the Seattle Spheres, green domes integrating a vast office complex built in the heart of the city). The possible increase in the cost of concrete that would result is not a concern. Currently, the average cost of concrete represents only 4.7% of the price of a building (although it constitutes 73% of its mass). A simple 20% increase in its cost would therefore represent only 6% of the total price of the building, which is largely amortizable provided that it is decarbonized.

Another promising solution lies in research into the recycling of existing concrete: a circular construction principle that automatically reduces the carbon impact of making new concrete and involves little energy cost to transform the recovered concrete, without loss of technical quality. “ The main cost is transportation,” says Edelio Bermejo, who concedes that a “change of mentality” is needed among customers. In Switzerland, many people already seem convinced, and Susteno cement, the first cement in the world made with 20% recycled materials, is already available on the Swiss market.

If you add to this a whole range of technological research (capturing and storing the CO2 released by concrete production – for example to produce synthetic kerosene; connected concrete or magnetizable concrete, allowing you to charge the battery of your telephone or even that of a bus; hydromedia concrete, for floors that absorb rainwater, as is already the case in a park in Aubervilliers), the myriad of tracks under development or already operational makes you dizzy.

New intelligent building systems


However, this overall strategy for sustainable and low-carbon concrete is not based solely on the material itself. Holcim has also chosen to use design to promote new, intelligent construction systems that can facilitate assembly and reduce the amount of material needed to produce the desired surface. A reflection that goes through all aspects of the building, from the roofs to the floors of the buildings, and even the urban furniture.

Landprocess Panoramic Studio

For roofing, Holcim offers a range of green roof systems under the Firestone brand name, which are particularly interesting for cooling and insulating homes in cities where the weight of urban development has been very high in recent years, particularly in Asia. The 22,000 square meters of roofs of the Tammassat University, near Bangkok in Thailand, are home to a system of cascading farms that naturally absorb rainwater, reduce the effect of urban heat, offer a short circuit of agricultural production and fight against energy loss through the roofs (on average 60% loss).

On the flooring side, Holcim has partnered with Block Research Group (BRG) of the ETH-Zurich to develop an innovative floor system that is very light in weight and easy to install/dismantle. The Rippmann Floor System is easy to assemble due to its geometric appearance in arch blocks, all of the same shape and modular. This system avoids the addition of integrated steel reinforcement, which promotes recycling. The shape of the blocks used allows them to be less dense, incorporating empty parts that make the structures both lighter and more ecological. The use of materials is reduced by half and thanks to the use of ECOPact green concrete and ECOPlanet green cements, the carbon footprint is reduced.

ETH Zurich, Digital Building Technologies © Andrei Jipa

In terms of structure, the Striatus Bridge was particularly noted at the last Venice Architecture Biennale. Like the Rippmann Floor System – which was also designed in collaboration with ETH Zurich, among others – it is based on an assembly of single blocks (53 in this case), specially designed to hold together thanks to compression and gravitation points. It does not use any glue or joints. Each element is placed at the precise location to allow for minimal use of decarbonated concrete. This extremely precise calculation and its very technical manufacture results there again from the use of 3D printers. An astonishing approach that allows Holcim to imagine production/marketing schemes… and to open up new perspectives.

3D printer builders


Indeed, Holcim is placing the use of 3D printers at the heart of several architecture and intelligent building systems projects conducted internationally and particularly in Africa through its 14trees business. In Malawi, an entire school was designed in 2021, using this fast and material-saving technology site system. The images are impressive. Imagine a giant printer tracing back and forth, then all around a rectangular shape, the stacking of concrete wall infrastructures necessary to build a real house!

Bennie Khanyizira

18 hours were necessary for this record-breaking design, which will obviously require others. In Kenya, to help meet the demand for rapid housing construction, Holcim has just launched an ambitious project of 52 housing units built using 3D printing. One more stone in the garden of sustainable and decarbonized concrete.

Laurent Catala