Recycled Cement: A Low-Carbon Alternative to Cut Emissions in Construction

The cement industry produces about 8% of global carbon emissions. But a new study suggests recycled cement can significantly reduce emissions without affecting structural stability. Researchers at the University of São Paulo and Princeton designed a method to recycle crushed concrete from demolished buildings, reducing landfill waste and greening construction.

Recycling Cement to Reduce Carbon Footprint:-
The construction industry generates massive amounts of waste, particularly from building demolition. Construction and demolition waste in the United States alone in 2018 was more than double the quantity of household waste. The waste is typically sent to landfill or used for low-grade applications such as road construction. The new study shows that waste concrete can instead be converted into high-quality cement, a green alternative.

The process entails heating crushed or pulverized concrete to 500°C. This is carried out in order to restore its cementitious property without releasing much carbon dioxide emissions, as opposed to the normal cement production where limestone is heated to 1,450°C. Nevertheless, recycling cement alone would result in the deterioration of concrete via porosity. To address this, scientists mixed it with Portland cement or limestone ground into fine particles, enhancing its strength and equal to that of regular Portland cement.

High Potential for Substantial Emissions Reduction:-
The recycling of cement has the capability of cutting down on carbon emissions significantly. Recycled cement, the research found, emits 198 to 320 kilograms of carbon dioxide per metric tonne—up to 40% lower than some of the existing low-carbon cements such as limestone calcined clay cement (LC3). Were this measure to be applied on a large scale, the emissions in the cement industry would be cut by up to 61%, more than double the anticipated 9% reduction through other means.

Besides emissions, the process also presents solutions to waste disposal through reuse of demolition waste that would otherwise cause landfill overflows. This is in line with circular economies, where materials are recycled and reused instead of being discarded.

Challenges in Adoption:-
Despite its potential, the large-scale use of recycled cement is encumbered by several challenges. One of the greatest challenges is the proper sorting and processing of demolition rubbish. Ensuring consistent quality in the recycled cement will require improvements in infrastructure and processing technology. Building regulations and building codes also need to be updated to allow for the use of recycled cement in traditional construction work. To our knowledge, only a few European and Latin American nations have begun introducing such standards.

Future Outlook:-
The cement industry has been under growing pressure to reduce its environmental footprint. With global construction needs projected to rise, sustainable options like recycled cement can play a crucial role in reducing emissions. Additional research, investments in technology, and policy reforms will be necessary, however, to roll this solution out on a broader scale.

If they can be overcome, recycled cement could be a low-carbon alternative to regular cement, putting the building industry on a more sustainable path.

Source: Princeton Engineering
Credits: Princeton and University of São Paulo researchers