Cement production is a significant contributor to CO2 emissions, accounting for 7 per cent of the total global emissions in 2018.
Cement is the binding element to concrete and indispensable to its production; it also accounts for 80 per cent of concrete production emissions.
Reducing emissions is the dilemma that the construction industry faces 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” talks about the issue and shows studies on various concrete technology and designs that can reduce emissions.
The new US administration’s promise to invest in big infrastructure projects while slashing emissions simultaneously served as an added impetus to these innovations, the article says.
The new concrete technology includes making CO2-infused concrete that locks up the greenhouse gas, which engineer claims are 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 amounts of cement by replacing it with industrial products like iron slags and coal fly ash will reduce carbon emissions 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 titled “Review on carbonation curing of cement-based materials” examined the use of CO2 as a curing agent. It finds that the use of carbonation for curing improved the physical performance and better resistance to freeze-thaw cycles and sulphate salts, and acids which is the usual cause 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. Concrete that is thinner and ductile and 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 of the small particles added that 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.
But before the construction industry can fully implement these technologies to reduce the emissions problem, life cycle emissions need to be further examined, the article says.
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 the concrete during curing and mixing. The study says that carbon capture and utilization of concrete production can sequester between 0.1 to 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 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 to remedy 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.