The construction industry is one of the world’s biggest sources of pollution, largely because it relies on materials like cement, sand, and gravel.
Producing these materials requires large amounts of energy and natural resources, contributing significantly to global carbon dioxide emissions.
As cities grow and construction demand increases, researchers are searching for new ways to build with fewer environmental impacts.
A research team from the Belmez Higher Polytechnic School at the University of Córdoba in Spain has developed a promising solution: a paving block made entirely from recycled waste materials.
Instead of using traditional natural aggregates such as sand and gravel, the scientists created a new material using crushed mollusk shells and mining waste.
Their findings were published in the journal Materials and Structures.
The researchers focused on shells from a type of edible saltwater clam called Acanthocardia tuberculata.
In Spain, these clams—often known locally as corruco or langostillo—are widely processed and sold in canned products. However, once the clams are removed, the empty shells become waste.
According to the research team, the canning industry produces large amounts of these shells every year, and most of them end up in landfills. Lead researcher Ágata González Caro explained that the team wanted to find a practical way to reuse this material instead of letting it go to waste.
To do this, the shells were crushed and processed into a type of calcareous aggregate. This material can perform a similar role to the natural aggregates normally used in mortar and concrete.
But the team did not stop there. Their goal was to create a paving block made entirely from recycled materials. To replace cement—which has a particularly high environmental footprint—they turned to other industrial waste products.
The researchers used waste from a mining spoil heap in the Guadiato Valley along with fly ash, a fine powder produced during coal combustion.
These materials were combined and treated through a chemical process called alkaline activation. When exposed to a highly alkaline solution, the mixture forms new compounds with properties similar to those of traditional cement.
By combining crushed mollusk shells with these recycled binding materials, the researchers produced a paving block that meets important performance standards. Tests showed that the blocks have the necessary strength, durability, and safety characteristics required for construction materials.
What makes the innovation particularly notable is that the paving blocks contain no natural raw materials at all. Instead, they are made entirely from industrial and food-processing waste that would otherwise need to be disposed of.
The project demonstrates how different industries can work together in a circular economy, where waste from one sector becomes a useful resource for another. In this case, seafood processing and mining by-products are being transformed into construction materials.
The researchers note that further work is still needed to improve certain aspects of the manufacturing process, such as compaction and the removal of molds during production. They are also exploring greener chemical activators that could reduce reliance on conventional chemicals.
Even so, the study offers an encouraging example of how creative recycling could help reduce the environmental impact of construction while giving new life to materials that would otherwise be thrown away.
