Turning CO2 into Sustainable Concrete

Innovation created by: UCLA

Presentation written by: Nazih Al Lababidi, n_lababidi@hotmail.com

Presentation supervised by: Assoc. Prof. Dr. Elena M. BARBU, elena.barbu@univ-grenoble-alpes.fr

 

1. Impact of cement production

A single industry accounts for around 5% of global carbon dioxide (CO2) emissions. It produces a material so ubiquitous it is nearly invisible: cement. Cement is the primary ingredient in concrete, which in turn forms the foundations and structures of the buildings we live and work in, and the roads and bridges we drive on.

The production of cement releases greenhouse gas emissions both directly and indirectly: the heating of limestone releases CO2 directly, while the burning of fossil fuels to heat the kiln indirectly results in CO2 emissions. [1]

2. Innovation by UCLA

To avoid catastrophic climate change, the world needs cleaner energy and CO2-neutral building materials. UCLA’s team is on the path to create just that. It turns one of the most harmful greenhouse gases into a sustainable resource, reducing the emissions from concrete production and putting the carbon dioxide we already have to good use. CO2NCRETE is fabricated using 3D printers supplied with carbon captured from smokestack flue gas in a process known as “upcycling.”

UCLA has brought together researchers from the fields of chemistry and biochemistry, materials science, mechanical, civil and environmental engineering, and economics. Their breakthrough technique of Carbon upcycling is based on the integration of several technologies into a closed-loop, to fabricate CO2NCRETE™. The process is designed to efficiently utilize flue gas exhausted from point source emitters (e.g., power plants and cement plants), by efficiently recovering waste heat and enriching CO2 present in the gas stream. A novel binder system based on calcium hydroxide (hydrated lime) is mixed with aggregates and admixtures to form a shape-stabilized CO2NCRETE™ building element. The final, and key step lies in combining the captured CO2 with CO2NCRETE™ element via a carbonation reaction (i.e., CO2-mineralization) to form a new type of CO2-neutral building material that can be used as a solid building component.

These elements can be used like Lego® to rapidly assemble buildings, bridges, and other infrastructure traditionally constructed with concrete.

The process for carbonating portlandite using captured carbon dioxide

Source: phys.org/news/2016-03-carbon-dioxide-sustainable-concrete.html

In fact, power plants are the largest source of carbon dioxide on the planet. The current approach to dealing with the CO2 they produce is to simply capture and store it. Upcycling goes a step further with UCLA by finding a use for that captured carbon.

By removing CO2 from power plant smokestacks this technology reduces the largest single source of greenhouse gas emissions. By creating a CO2-neutral building material it also displaces cement. Once commercialized, this technology offers a much lower-CO2 emissions trajectory for the construction and power sectors across the globe while promoting environmentally sustainable growth.

Conclusion

The future of construction needs advanced material systems to enable leaps forward in constructability, structural efficiency, and resilience. As a material, CO2NCRETE™ is designed to meet these goals with its adaptability to a wide array of forming and manufacturing techniques, rapid strength development, and Lego®-like assembly. While CO2NCRETE™ may be hand-molded similar to traditional concrete, its unique reaction mechanism makes it readily adaptable to additive manufacturing techniques (i.e., 3D-printing). The accelerated strength gain by carbonation, coupled with the tight quality controls and efficiency of the CO2NCRETE™ prefabrication paradigm will accelerate construction timelines, while reducing labor intensity.

References

Rubenstein, Madeleine. “Emissions from the Cement Industry.” State of the Planet Emissions from the Cement Industry Comments, May 2012, blogs.ei.columbia.edu/2012/05/09/emissions-from-the-cement-industry.

“Researchers Turn Carbon Dioxide into Sustainable Concrete.” Phys.org – News and Articles on Science and Technology, phys.org/news/2016-03-carbon-dioxide-sustainable-concrete.html.