Innovate The unsustainable unsustainability of the concrete Research centres and start-ups team up with industry bigwigs to offer an alternative to this material, still so used in construction, however polluting it may be. Small, high-tech signals of a possible future revolutionCement is the world’s no. 2 commodity by weight after water. According to the Cement 2022 Report, global production of cement in 2022 was 4.37 billion tons, of which 4.27 billion tons were consumed (+6% over 2021), producing 14 billion cubic metres of concrete. A booming market (roughly $ 330 billion in 2021 and projected to grow to 444 billion cubic metres in 2027) for a material that is still indispensable for the construction industry, but one that costs the world a pretty penny: cement production contributes up to 7% of global CO2 emissions. To produce one ton of cement, the material is heated to 1,400°C, which releases close to a ton of CO2. This process, which has remained substantially unchanged since cement was first produced over 200 years ago, is the source of 70% of emissions, while the remaining 30% comes from the energy used to keep the processing kilns in operation. And if we add to this the CO2 produced by transporting, constructing, and post-demolition disposal, the paradox is clear: the obvious unsustainability of a material that is unfortunately indispensable since it “sustains” nearly everything we build in the world. Researchers at ETH Zurich have developed a system of 3D-printed formwork elements. London design studio Newtab-22 has developed a concrete-like material made using waste seashells from the food industry, which are ground up and combined with a patent-pending mix of natural binders such as aga. The University of Tokyo could produce cement from food waste. The Dutch start-up Claybens has developed the production of building materials derived from firing clay soil contaminated at very high temperatures, that makes it possible to clean up large quantities of soil.A spate of increasingly strict emissions regulations and equally stringent ESG policies guiding industrial finance, coupled with growing awareness and concern about these issues, drive the raw materials industry in the only feasible direction: not so much building less as building better, investing in technology and research to develop materials that can provide the same (or even better) performance and functions in infrastructure with a lower environmental impact. A utopia? Scanning the horizon of university research efforts, research consortia, and R&D centres of the big players, we observe a number of interesting experiments, small but highly technological signals of a possible future revolution.An interesting – and in some ways visionary – example is found at the Materials Research Center of the Department of Engineering of the University of Colorado-Boulder, where experimentation is underway on zero-emission concrete. The principle behind the study is the total replacement of the cement component with calcium carbonate produced by algae, a natural by-product of photosynthesis. According to the researchers, the resulting material is carbon neutral, in that the carbon dioxide released during the production of the new cement is equal to that removed from the atmosphere during the growth process of the algae. The research team has received a grant of 3.2 million dollars from the U.S. Department of Energy to continue its research. Of course, while it is unquestionably a very interesting “circular” solution, it is one thing if it works in a university laboratory, it is another thing to get it to work on a real-world scale: to meet demand for cement in the United States, four thousand square kilometres of wetlands dedicated exclusively to intensive algae production would be necessary. No simple matter. In the University of Colorado-Boulder, experimentation is underway on zero-emission concrete. The principle behind the study is the total replacement of the cement component with calcium carbonate produced by algae, a natural by-product of photosynthesis Wil Srubar, director of CU’s Living Materials Laboratory at University of Colorado-Boulder. With his team has found a way to make cement using limestone that was grown by algae through photosynthesis. Living Materials Laboratory at University of Colorado-Boulder has found a way to make cement using limestone that was grown by algae through photosynthesis. As part of the ACORN project, researchers from the universities of Bath, Cambridge and Dundee have developed a thin-shell vaulted flooring system, which can be used to replace traditional solid floor slabs while using 75 per cent less concrete to carry the same load. As part of the ACORN project, researchers from the universities of Bath, Cambridge and Dundee have developed a thin-shell vaulted flooring system, which can be used to replace traditional solid floor slabs while using 75 per cent less concrete to carry the same load.Another outfit focusing on the use of biomaterials is Newtab 22 in London, which is experimenting with a new product similar to cement produced using waste mollusc shells from the food industry. Ground up and mixed with natural binders, they produce a satisfactory alternative to cement, supplying the calcium carbonate that is necessary for the production of concrete. While the effort is certainly interesting, scalability is again an issue, with the magnitude of global demand tending to dampen enthusiasm. The production of this natural cement depends on supplies of resources which, while natural, are not renewable at the needed scale: the food industry produces only limited amounts of this waste. Construction materials on the public market require licenses and international certification that are unlikely to be granted to materials that—once the available waste materials have been consumed—would cause the depletion of marine fauna.A more conservative but equally interesting approach has been proposed by researchers at the universities of Bath, Cambridge, and Dundee as part of the Automatic Concrete Construction (ACORN) project. The principle here is the possibility of reworking cement not so much in its chemical composition as in its structure. Taking advantage of the high performance now achieved in parametric and computational design, it is possible to optimize the volume of material that is structurally necessary. The multidisciplinary team at the Department of Civil Engineering of the University of Cambridge has built a spiral vault using a very thin layer of cement. Exploiting the resistance of the material to compression, they were able to reduce the amount of concrete by 75% with respect to a traditional flat structure, which requires significant slab thickness to overcome concrete’s limited resistance to bending. In a vaulted structure, the weight is transmitted along the arc and there is no need for reinforcement, only a layer of standard flat raised-flooring panels. The idea is powerful for its simplicity and may have the potential to revolutionize infrastructure design. Hot mixing: the start-up from ancient RomeWhat is the most advanced technology to make structures and infrastructure stronger and longer lasting? It was invented more than two thousand years ago, and only rediscovered last December, when a study by chemist and researcher at MIT in Boston, Admir Masic, was published in the journal Science Advances. The secret that has kept spectacular structures such as ancient Roman aqueducts, bridges, and amphitheatres in excellent condition over centuries and millennia is called “hot mixing”. This technique for producing construction materials consists in adding quicklime to the concrete mix. The quicklime reacts with water and heats the cement, causing calcium granules to form, and these micro-granules are precisely what ensures the longevity of the structures. How does it work? Generally speaking, and for various reasons, tiny cracks can form in the structure, and water or moisture inevitably manages to penetrate. With seasonal heating and freezing, the water tends to enlarge the crack in normal concrete, eventually compromising the integrity of the entire structure. However, with the hot mixing technique, the calcium granules dissolve in contact with water and then the calcium ions recrystallize to fill the crack, beginning a natural self-healing process. Using this ancient knowledge, Admir Masic (Bosnian) and Paolo Sabatini (Italian) founded the deep tech company DMAT, which is now producing D-Lime, technologically advanced concrete using the hot mixing process, which produces more durable, higher quality concrete structures thanks to its self-healing capacity. This new generation concrete achieves a 20% reduction in CO2 emissions over its lifecycle and has been certified in Switzerland by the Istituto di Meccanica dei Materiali SA.A technology invented over two thousand years ago, which no one had ever discovered until December 2022 Geopolymer concrete made in NorwayNorwegian startup Saferock, in partnership with the University of Stavanger and architectural studio Snøhetta, is working on the development of geopolymer concrete, a type of inorganic polymers consisting of minerals, typically stemming from waste streams from mining industries and power plants. This new kind of concrete could represent an sustainable alternative to the product made of Portland cement that is in use today, and provides a unique opportunity where mining waste has previously posed an environmental threat. To date there has been no real use for the waste materials from mining: they have had to be dumped, thus representing a major hazard to the environment – partly because of the toxic matter emitted by this mixture of minerals. “The products of mining should be used as extensively as possible and for this to happen, we need to change our understanding of which materials we see as waste”, said Stian Alessandro Ekkernes Rossi (below and right), formerly an architect at Snøhetta, has now moved to Saferock. “Our multiplex solution is based on on-site production, eliminating both transport emissions and -time. This provides a unique opportunity where mining waste has previously posed an environmental threat. We aim for our technology and materials to be part of a circular ecosystem. This will truly impact the industry’s environmental footprint”. The production of geopolymers has a CO2 footprint that is at least 70% lower compared to the production of traditional Portland cement (reference values from the Norwegian Concrete Association). In addition, geopolymers have several properties that are favorable compared to concrete based on Portland cement for certain applications, such as higher temperature and chemical resistance and significantly lower permeability. Along with its chemical and physical characteristics, this cement substitute also demonstrates new possibilities in terms of design, with the color of geopolymer concrete varying depending on mineral composition – from reddish or yellowish to various anthracite hues. Buildings made of or restored with the material are thus furnished with their own geographic identity.by Alessandra Marino (from “DomusAir” n.7 – march 2023)Stian Alessandro Ekkernes Rossi, formerly an architect at Snøhetta back to top
