Concrete Technology that Reduces Carbon Emissions

Cement production significantly contributes to CO2 emissions, accounting for 7% of the total global emissions in 2018.

Cement is the binding element in concrete and indispensable to its production; it also accounts for 80 per cent of concrete production emissions. 

Reducing emissions is the construction industry’s dilemma as it tries to reduce its carbon footprint to prevent climate change. Concrete production is not expected to slow down after at least two decades.

An article from “The Conversation” discusses the issue and shows studies on various concrete technologies and designs that can reduce emissions.  

The article says the new US administration’s promise to invest in big infrastructure projects while simultaneously slashing emissions served as an added impetus to these innovations.

The new concrete technology includes making CO2-infused concrete that locks up greenhouse gases. The engineer claims the concrete is more robust and even bendable.

Below are example studies on the new concrete technology that has the potential to slash carbon emissions.

• A study by Vijayaraghavan, J. et al., titled “Effect of copper slag, iron slag and recycled concrete aggregate on the mechanical properties of concrete,” says that reducing the amount of cement by replacing it with industrial products like iron slags and coal fly ash will reduce carbon emissions and produce concrete with higher mechanical strength.
• A study, “Calcined clay limestone cements (LC³)” by Scrivener, K., et al. finds that using alternative binders like limestone calcined clay reduces cement use, 20% emissions, and production cost.

Another study, “Review on carbonation curing of cement-based materials,” examined using CO2 as a curing agent. It finds that using carbonation for curing improves the physical performance and better resistance to freeze-thaw cycles and sulphate salts and acids, which are the usual causes of concrete degradation and cracking. This method is already used by concrete manufacturers, either at construction sites where concrete is poured directly or in precast concrete plants.

The University of Michigan is also working to produce bendable concrete. Thinner and ductile concrete needs less steel reinforcement, which can reduce emissions. Bendable cement can also significantly reduce fractures and thus avoid costly repairs.

According to the article, bendable concrete can absorb more CO2 because the small particles added react to CO2, turning it into minerals. Bendable concrete was used to make Japan’s 61-storey building for earthquake resistance and Ypsilanti, Michigan’s roadway bridge slabs.

The article says that life cycle emissions need to be further examined before the construction industry can fully implement these technologies to reduce the emissions problem.

The study “Carbon dioxide utilization in concrete curing or mixing might not produce a net climate benefit” examined the lifecycle emissions from infusing CO2 into concrete during curing and mixing. The study says that carbon capture and utilization in concrete production can sequester between 0.1 and 1.4 gigatons of CO2 by 2050.

Still, these estimates do not account for the CO2 impact from the capture, transport, and utilization of CO2 and the change in the compressive strength in carbon–infused concrete—data showed that CO2 curing decreases a concrete’s compressive strength compared to conventional concrete.  

Researchers proposed remedying these barriers by developing a standard CO2 curing protocol, as various curing procedures and concrete mixes exist. Research can also improve the curing process to increase concrete’s performance. The use of electricity during curing—which is also a significant source of emission—can be reduced through streamlining with the possible use of waste heat.