Researchers at the University of Córdoba have developed a paving block made entirely from industrial waste. The innovation replaces both natural aggregates and conventional cement with recycled materials. The result is a more circular and potentially lower-carbon construction material for urban surfaces.

Shell Waste As A New Construction Resource

The construction industry contributes significantly to global CO₂ emissions and consumes large amounts of non-renewable resources such as sand and gravel. Because demand for construction materials continues to grow, the sector is actively exploring alternatives with a smaller environmental footprint.

A research team from the Belmez Higher Polytechnic School at the University of Córdoba addressed this challenge by creating paving blocks from recycled waste streams. Their approach replaces natural aggregates with crushed mollusk shells from Acanthocardia tuberculata, an edible saltwater clam widely used by the canning industry.

Large quantities of these shells are discarded during food processing. They often end up in landfill because they have little industrial value. By crushing the shells, the researchers produced a calcareous aggregate suitable for mortar and concrete applications.

Mining Waste As A Cement Alternative

The research team also replaced conventional cement in the paving block. Cement production is responsible for considerable CO₂ emissions, making it a key target for decarbonisation in the construction sector.

Instead of cement, the researchers used waste from a spoil heap in the Guadiato Valley mining area, combined with fly ash. They then applied a process known as alkaline activation. In this process, the materials react with a highly alkaline solution and form compounds similar to those found in cement.

This method creates a strong binding matrix without relying on traditional cement production.

Circular Opportunities For Urban Design

The resulting paving block contains no natural raw materials. Instead, it uses waste streams from both the food processing and mining industries. Laboratory tests show that the blocks meet mechanical strength, durability and safety requirements for paving materials.

For architects and landscape architects, the material demonstrates how industrial by-products can become valuable resources for urban infrastructure. Recycled paving solutions could help reduce landfill waste while lowering the environmental impact of public space design.

The researchers note that further development is still needed. Future work will focus on improving manufacturing processes such as compaction and demoulding. The team also plans to explore greener chemical activators to further reduce environmental impact.

Even so, the study highlights the potential of fully recycled construction materials within a circular building economy.

Source: EurekAlert! / University of Córdoba
Photo: Wikipedia