Researchers from the University of São Paulo and Princeton University have developed a method for repurposing cement waste into a low-carbon alternative with properties comparable to traditional Portland cement.
How does recycled cement technology work?
The key to the new process is applying heat at 500°C to the pulverized concrete waste, restoring its binding properties without emitting as much CO₂ as other processes , then mixing it with a little Portland cement or limestone to strengthen it.
According to the article published in ACS Sustainable Chemistry & Engineering , this reclaimed cement can form mixtures with up to 80% recycled content and maintain the structural strength demanded by the industry.
Claire White, a professor of civil engineering at Princeton, noted that combining recycled powder with smaller amounts of conventional cement or limestone improves porosity, reduces water demand, and increases the mechanical strength of the final material.
A cleaner approach to cement
The production of this recycled cement is estimated to generate between 198 and 320 kg of CO₂ per tonne, representing up to 40% less emissions than other low-carbon commercial solutions such as calcined clay cement.
Furthermore, the use of demolition waste contributes to the circular economy by reducing the volume of waste sent to landfills and recovering materials for new construction. Sérgio Angulo, a professor in São Paulo, emphasizes that it’s a direct way to close the loop on urban infrastructure materials.
Barriers and next steps for concrete recycling
Despite its benefits, scaling up this technology will require improvements in construction waste sorting and treatment. It will also require updating building codes, which are still based on traditional Portland cement-centric recipes rather than performance standards.
Several countries have already begun to adopt more flexible standards. In Brazil, for example, performance requirements are being implemented for nonstructural elements. This regulatory liberalization could allow for broader adoption of recycled cement and other sustainable solutions .
An alliance to innovate in construction
The collaboration between Princeton and São Paulo has allowed for the combination of expertise in materials characterization and practical application. This synergy has facilitated advances in both the atomic understanding of the thermoactivation process and the validation of mechanical properties.
Researchers believe this development could lay the groundwork for a new generation of building materials : more sustainable, with a lower carbon footprint, and ready to meet the demands of a planet in need of long-lasting solutions.
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Source and photo: Princeton University
