The cement industry, fundamental for the construction and responsible for around 8% of global CO₂ emissions, faces a critical challenge in its transition towards more sustainable practices.
Engineers from the University of São Paulo and Princeton have developed an innovative technology to recycle cement waste, offering a low-carbon alternative with performance comparable to traditional Portland cement.
## The problem with Portland cement
The production process is highly polluting. It generates large amounts of waste, with 1 Gt annually, exceeding the availability of supplementary cementitious materials (SCM).
The cement waste is heated to 500°C to recover its reactivity. However, this technology has limitations due to the high water demand of the recycled thermoactivated cement (CR).
## Engineered Recycled Cement (eCR)
Study proposal: Use CR as the dominant component (>75% by weight), combined with small amounts of finely ground Portland cement (<20%) or limestone.
Performance: This recycled binder demonstrated early and late strength properties comparable to ordinary Portland cement (OPC).
Emission reduction: Emits between 198 and 320 kg of CO₂ per ton, significantly less than conventional Portland cements. Mixes with up to 80% recycled cement equal the strength of Portland cement while reducing the carbon footprint.
## Potential Impact
If this technology is widely implemented along with other strategies, such as CO₂ capture through carbonation of cement waste, it could mitigate 61% of projected emissions for 2050 (2.31 Gt of CO₂/year). This advancement surpasses the 9% reduction projected by the Global Cement and Concrete Association with traditional methods.
## Reuse of waste towards sustainable construction
In addition to reducing emissions, eCR offers a solution to reuse construction and demolition waste:
– In 2018, in the United States, construction waste doubled household waste.
– With this technology, materials from demolished infrastructure can be transformed into resources for new projects, promoting more circular cities.
## Challenges for implementation
Despite its benefits, researchers identify obstacles for large-scale adoption:
1. Waste classification and processing: Requires advanced infrastructure to ensure material circularity.
2. Application in specific contexts: More viable in established cities with old buildings than in rapidly developing areas.
3. Updating building codes: Migration from recipe-based standards to performance-based requirements is necessary.
## International Advances
In some countries in Europe and Latin America, performance-based standards are already being adopted, which could facilitate the integration of recycled cements like eCR and other low-carbon alternatives.
Do you already know our YouTube channel? Subscribe now!
