Most promising decarbonisation routes for clinker, cement and concrete?

Question

Clinker is a major component of cement, which is a major component of concrete. Which means the production of clinker, globally, is huge.

But currently, clinker production releases very large amounts of carbon dioxide.

I know Stuart Licht's group at George Washington University, and others, have been looking at alternative production methods for clinker that would decarbonise the production of cement and concrete; others are looking at substitutes for clinker.

What are the most promising routes for decarbonising this sector, in terms of preserving the best qualities of cement and concrete as much as possible, including the economics and scalability?

Answer 1

Magnesium Oxide based cements are interesting.

Here are the downsides when compared to portland cement:

• They cure extremely fast so transporting pre-mixed cement doesn't work out.

Here are all of the upsides when compared to portland cement:

• They are produced at a lower temperature and release less CO2 during the process than when compared to portland cement. MgO cement can be produced in lower temperature processes and as part of seawater desalinization operations.
• It is cellulose-philic, meaning that it will get sucked up into and penetrate into cellulose fibers. Portland cement is cellulose-phobic and will be repelled by cellulose.
• Magnesium Oxide cement when combined with cellulose fibers will create an extremely strong matrix (stronger than steel reinforced portland cement). This allows for direct sequestration of Carbon in the form of cellulose fibers. When combined with an annual fiber crop such as hemp the resulting hempcrete blocks would be extremely strong and economical.
• Magnesium Oxide continues to absorb CO2 over time, and as it does it gets stronger. There are Magnesium Oxide buildings that are thousands of years old that are still standing, while portland cement starts decaying in a mere hundred years.
• Magnesium Oxide cement breaths water vapor but repels condensed water. This gives it the same phase change material properties that you get with adobe and rammed earth resulting in passive cooling and heating. Portland cement does not breath at all.
• The fast cure time is beneficial when manufacturing prebuilt sections in an assembly line. Also, note that it is also suitable for small batch mixing.