In a bid to reduce the carbon dioxide (CO₂) emissions produced by the construction industry, researchers at the University of Córdoba have developed a paving block derived from mollusk shells.

Traditionally, building materials used in the construction industry tend to be composed of nonrenewable resources such as sand and gravel. As such, the researchers sought to develop low-carbon-footprint materials.

Specifically, the team replaced traditional mortar and concrete aggregates with a shell-based material made from Acanthocardia tuberculata, an edible saltwater clam commonly canned and sold commercially.

"The canning industry generates tons of this waste, which ultimately piles up in landfills," explained the researchers.

To accomplish this, the team crushed the shells of this mollusk to create a calcareous aggregate to replace the natural aggregates in mortar and concrete.

Further, beyond replacing the aggregate with one derived from mollusk shells, the team replaced the remaining components to develop a paving block composed entirely of recycled materials. For instance, the team replaced the cement with waste from a spoil heap at the Guadiato Valley mine and fly ash. When the mix underwent a process known as alkaline activation, which occurs via contact with a highly alkaline solution with a very high pH, new compounds similar to cement were produced.

The final product, according to the team, was a durable paving block that meets the mechanical, durability and safety criteria necessary for such materials that only uses the leftovers and waste of other industries and not a single natural ingredient.

An article detailing the material, “CO₂-cured alkali-activated pervious paving blocks incorporating seashell sand,” appears in the journal Materials and Structures.