Engineers at the University of São Paulo and Princeton have developed an innovative method for recycling cement waste that produces low-carbon, sustainable cement instead of traditional cement. This process not only reduces the carbon intensity of the cement and concrete industry but also opens up new applications for construction and demolition waste, particularly concrete, which is a major component of this waste. In this study, the researchers demonstrated that mixtures containing up to 80% recycled cement are as strong as conventional Portland cement while emitting significantly less carbon dioxide.
The recycling method is based on heating recycled cement powder to a temperature of 500°C, which restores its binding properties without causing carbonate decomposition that would lead to CO2 emissions. Although recycled cement alone performs poorly in concrete mixes, combining it with some Portland cement or limestone improves its strength and performance, bringing it closer to industry standards.
The researchers estimated that if this process is fully implemented, it could reduce greenhouse gas emissions from the cement industry by up to 61%, which is significantly higher than the reductions predicted by alternative low-carbon cement methods. This approach, by reusing construction waste, contributes to the realization of a circular carbon economy and produces fewer carbon emissions than other low-carbon cement alternatives.
However, for the widespread adoption of this technology, the researchers noted that changes are needed in how construction waste is processed and updates to building codes. In this regard, some countries, such as Brazil and European nations, are implementing performance-based standards instead of specifying particular cement compositions, which could help facilitate the broader acceptance of this technology.