Rebuilding the Future with Recycled Concrete

The construction industry—responsible for the buildings we live in, the bridges we cross, and the harbours we sail from—is under pressure to shrink its carbon footprint without compromising material quality. Two recent technological breakthroughs suggest that a more sustainable, circular model is within reach. One key lies in the use of recycled concrete — but also in a shift in perspective, where the entire life cycle of a building, including its second life, comes into focus.

Recycled concrete: lower emissions, same performance

A significant share of the sector’s carbon emissions comes from concrete—especially the cement it contains, which is notoriously energy-intensive to produce. While efforts are underway to develop greener concrete mixes, researchers are also exploring how recycled cement could play a key role. That is the approach taken by a team from Princeton University, working in collaboration with the University of São Paulo.

Their innovation involves a method for reclaiming cement from demolition waste. By applying thermal activation at 500°C and combining the result with small amounts of Portland cement or limestone, they have created a mix that retains the strength and workability of conventional cement—but with up to 40% lower CO₂ emissions per tonne produced.

This advance not only cuts emissions but also supports a more circular approach to construction, where materials from old structures are reused in new urban developments. However, scaling this up depends on better systems for sorting construction waste. That is where another recent project comes in.

HISER: a circular approach to construction

As with any recycling system, success hinges on efficient sorting. In the case of municipal waste, technologies such as robotics and artificial intelligence are already being explored to boost sorting performance.

Construction waste, however, brings added complexity: it contains a wide range of materials—wood, plastics, glass, cement, metals—and buildings are usually demolished at the end of their lifespan, often without prior preparation. A project that takes these challenges into account may help change the game.

That is the goal of the European initiative HISER (Holistic Innovative Solutions for an Efficient Recycling), which has developed integrated strategies to maximise the recovery of raw materials from construction and demolition waste (CDW), including recycled aggregates. Its achievements include:

• The development of tools like BIM-SD for inventorying and classifying materials during demolition.
• Advanced separation and recycling technologies capable of recovering raw materials with 80 to 100% purity.
• New sustainable construction materials, such as low-emission cements, green concretes, and plasterboards and bricks made with high levels of recycled content.

These solutions have already been successfully tested at scale—notably by ACCIONA in Madrid, where the technologies were applied to gypsum and stone waste streams, boosting the circular use of materials and reducing the demand for virgin resources.

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Sources:

• Princeton University