Circular Economy, Concrete and Cement. Where are we now?

Circular economy is a trending topic among some industries. However, many challenges are still going on with this system and it is a source of many debates…

For cement and concrete industries, circular economy is attractive for environmental reasons, because we know that the production of one ton of cement rejects between 0.8 and 1 ton of CO2.

What has been done so far ?

In previous decades, the cement and concrete industries have implemented some techniques and methods that can be considered to be part of the circular economy.

Supplementary Cementing Materials (SCM)

Nowadays, many types of concrete (almost all of them) have SCM like Silica Fume, fly ash or blast-furnace slag in their mixture. These SCM are respectively coming from silicon production, carbon combustion and cast-iron production. Furthermore, theses materials increase concrete’s mechanical properties and durability if they are used intelligently.

Other concrete mixtures are in development, such as glass powder or rice husk ash.

Cement Production

Cement producers need to reach 1450°C in their oven to be able to transform raw materials in the clinker to then have cement. Combustibles to heat the oven can change and waste can be used. It was the case with used tires in Quebec, Canada, and it is still in the news. When the mad cow disease epidemic took place in 2000, some authorities paid cement producers to burn meat and bone meal and sick cows for the combustion of their ovens.

Recycled Concrete

Recycling concrete is not a new topic. Concrete form demolition rubble is not considered as waste and is frequently reused. In Belgium, minimal mandatory quantities of demolition rubble should be used in road construction works.

Some laboratories are investigating how to incorporate the demolition debris from this rubble directly into the concrete mixture.

Startups

Startups decided to be part of the game too. This is the case with CarbonCure. Their idea is to inject CO2 into fresh concrete. CO2 is coming from neighboring polluting industries which is then liquefied and delivered to the concrete producer in partnership of the company.

The risk? To change concrete properties when it is already hardened. CarbonCure says the injection of CO2 does not affect concrete properties.

This is another example of closing the loop of circular economy.

What are the problems ?

Mediator

The first one is to say that many solutions are possible when a circular economy system is going to be set in an industry. That’s why some conflicts can be generated when it is necessary to choose between different solutions. This is what happened in Nova Scotia, in Canada. Lafarge Canada proposed the idea of burning used tires for their cement production to the Environment Minister. The other possibility was to recycle them.

“Burn or Recycle, that is the question”

We do understand why a complete study of cost and environmental impacts is necessary to take the best decision without creating a conflict of interest.

Profitability

To use materials considered to be “waste” by other industries can be more expensive than the initial solution. The price of Silica Fume is an example. However, the added value, mechanical improvements for example, brought by these products allows the quantity of the mixture to be reduced. It is a source of savings. Quality increases and maintenance costs are reduced.

But you need to convince shareholders.

The Wolf

Changes

Habits changing in a company or a public institution are a source of problems because they bring modifications and more work.

Here is a list of modifications that can take place:

  • Equipment
  • Employees (replace or training)
  • Methods and processes
  • Standards

Moreover, circular economy means that industries that initially did not work together must now work as one. The glass industry is an example.

Conclusion

The circular economy picture has for sometime been linked to a Stone Age economy. However, this vision is not true for cement and concrete industry. The performance of materials are increasing as we have already mentioned. Problems are still present at different levels, from small businesses to public authorities, but solutions are created everyday to solve them.

Innovation has quite often been serving growth despite environment. Nowadays, it can serve both.

Samuel Faucon

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