The search for construction elements that move away from classic materials such as steel, concrete or cement makes sense from different fronts ranging from economics to sustainability through technical limitations. Without going any further, we can already see skyscrapers made of wood and some even compete to be the tallest in the world. Yes, wood is proposed as a serious alternative, but you can also give a twist to cement as we know it with a new old acquaintance: the shells on the beach.
From waste to concrete ingredient. Seashells that are normally treated as waste can become a kind of substitute for the cement used for concrete, as a published study by the University of East London has concluded. in Construction Materials magazine.
In fact, they can act both as a filling material and as a partial substitute for cement. Thus, microstructural analysis revealed that the shells, which are rich in calcium, help refine the porous structure of the concrete and promote the formation of additional binding compounds, that is, it even provides additional benefits in terms of performance.
under the microscope. Scallop shells are composed by a range of 95 to 99% calcium carbonate (like limestone, the raw material for cement) presented in two crystalline forms, calcite and aragonite. The other 1-5% is the organic fraction, which serves as cement to bind the calcium crystals. The shells are a sort of biogenic limestone, chemically compatible with cement, which is still a hydraulic binder of limestone and clay.
Up to 36% less cement. The process is also quite “simple”: grinding scallop shells to turn them into a fine powder suitable to replace part of the cement mixture. How much? Up to 36% without substantially altering the characteristics of the concrete.
Why is it important. The partial replacement of cement with a natural waste material such as shells is an unexpected and novel solution to reduce the environmental impact of cement, currently responsible for approximately 7% of global carbon emissions. This percentage is so high not only because of the fuel required to heat the furnaces, but also because of the chemistry of the process itself. In fact, already has been experimented with ecological mortar.
The person responsible for the study, the associate professor of Structural Engineering at the UEL and doctor Ali Abass contributes more context: “Concrete is everywhere and, consequently, its carbon footprint is enormous.” Regarding its applicability beyond the study, Abass is optimistic: “At moderate levels of substitution, concrete performs very well, meaning this solution could be scaled in real-world environments.” In addition, two problems are solved at once:
“Millions of tonnes of shell waste are generated around the world every year, and most of it has no useful destination. If we can divert even a fraction into low-emission building materials, the environmental benefits could be significant. It’s a simple idea with real potential to transform part of the sector.”
A giant step towards more sustainable construction. In short, the use of shells would allow us to cut significant amounts of CO₂ from one of the most polluting materials in the world and move towards more sustainable construction. In the absence of future industrial trials to support large-scale reliability, its adoption potential is notable, especially at a time of increasing calls for stricter environmental standards and scrutiny over carbon footprint calculations.
Cover | Rodolfo Quiros and Pok Rie
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