Emission of Carbon in Cement Production

Cement is a fundamental building material used around the world. Approximately 2.35 billion tons are produced every year and this production accounts for 5 to 10 percent of the carbon dioxide emissions around the world. A simple 10% reduction in the amount of carbon dioxide produced would meet 20% of the Kyoto Protocol greenhouse gas reduction goal.

Research Work                                                                                                                                                            Getty Images/VGI-H

Cement is a major component in one of the oldest and the worlds most widely used construction material, concrete. Researchers from around the world with backing by cement manufacturers are examining the nanostructure of concrete with an eye to reducing CO₂ output.  The research work has shown that the key to the strength and durability of concrete comes from the organizational structure of nanoparticles.

How Cement is Made?

Cement is made by crushing limestone and clay into a powder and then by heating to around 1500°C in a kiln. When the cement powder is mixed with water calcium-silicate-hydrate (C-S-H) is produced that acts as a glue to bind together the other components in concrete, sand and gravel. Most of the problematic CO₂ is produced as part of the heating process.

“Concrete and cement needs to lose colossal carbon footprint”

Research Advancement
With samples taken from all around the world, researchers used a nanoindentation technique to measure strength at the nano level. They found that all the samples showed a unique nanosignature for the C-S-H material regardless of the sample origin. This is known as the material’s genomic code and means that the strength of cement paste is not a function of specific minerals but relates to the way the nanoparticles are arranged.

“If everything depends on the organizational structure of the Nanomaterials that make up concrete, rather than on the material itself, we can conceivably replace it with a material that has concrete’s other characteristics–strength, durability, mass availability and low cost–but does not release so much CO₂ into the atmosphere during manufacture.”

Nanostructure of Concrete

Recently researchers found that the nanostructure of cement is organised into a pyramid like shape, the most densely packed structure for spherical objects. Now that the secret behind the strength of concrete has been revealed the next step involves turning to nanotechnology to nanoengineer a material for use in the cement paste. This replacement material will be required to have the same packing density but not require the high production temperatures needed to produce standard cement. Advance­ment in the emerging field of nanoengineered concrete. urgently needed which can be readily applied in a more sustainable construction industry to achieve the carbon neutrality. 

Replacement Material

Depending upon global distribution of the new material it could reduce world carbon dioxide emissions by up to 10 percent. Additionally, depending upon the material used, the amount of carbon in the atmosphere could be reduced even further. Current research is investigating the replacement of calcium in cement with magnesium. Technological changes can be accelerated through regulation and legislation. Magnesium based nanomaterials incorporated into cement will also solve other environmental problems. Magnesium is an industrial waste product that requires managed disposal. A cement incorporating magnesium has already been developed in Australia. Marketed as Eco-cement, this material is a composite of the magnesium compound, magnesite, recycled industrial waste and ordinary cement.As Eco-cement sets and hardens, it absorbs CO₂ from the atmosphere and the magnesite converts it to carbonate. This process continues for roughly a year, before the power of the porous magnesite to convert CO₂ is exhausted.