Recycled Cement Cuts Emissions Without Strength Loss, Says Study
Experts from Brazil and Princeton collaborate, bringing their expertise in cement chemistry and material characterisation.
The aim is to adopt a circular economy model in the cement and construction industry.
A group of researchers from the University of São Paulo and Princeton has developed a new way to reduce waste from demolished buildings, creating a low-carbon alternative to traditional cement.
Their process gives construction materials a second life without reducing their strength, equivalent to that of standard Portland cement. The analysis says this method will significantly reduce carbon emissions in the cement and concrete industry, which now accounts for around 8% of global emissions.
According to researchers, a key advantage of this method is its ability to reduce landfill waste by repurposing demolished concrete. In the U.S., in 2018, waste generated from construction and demolition was more than double the amount of household waste. Usually, concrete waste is either dumped or used in low-grade applications like pavement construction. The research found that recycled cement could instead be used in high-quality applications, making it more sustainable.
READ MORE: Concrete Buildings in Japan Act As Carbon Sinks: Study
What process do researchers use?
After collecting pulverised or crushed concrete, it will be heated at 500°C. This temperature is sufficient to bring back the cement's binding properties without emitting additional carbon dioxide. But when the recycled cement is used alone, it will give rise to weaker concrete due to high porosity. To resolve this problem, the researchers blended it with small amounts of finely ground Portland cement or limestone.
If we could widely adopt this method, the researchers say, the cement industry can reduce emissions by up to 61%, much higher than the 9% reduction predicted by other methods.
Recycled cement is expected to emit between 198 and 320 kilograms of carbon dioxide per metric tonne, up to 40% lower emissions than some existing low-carbon types of cement, including limestone calcined clay cement (LC3).
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However, there are challenges to be dealt with. For instance, efficient sorting and processing of demolition waste play a larger role in scaling this technology. Also, current building codes have to be updated. So far, only some countries in Europe and Latin America have started implementing such standards.
For a detailed analysis of the research, click here.
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Source: Princeton Engineering
