What is low-carbon cement and how does it differ from regular cement?
When it comes to cement, the part that produces the most CO2 is clinker. Clinker is produced in huge kilns, which are essentially big, long tubes. It is usually ground to a powder, resulting in cement. Some clinker – the CO2-intensive part – can be replaced with other materials. The most common substitute is blast furnace slag, a by-product of iron production and fly ash, which comes from coal-fired power stations. The problem is that there is a relatively small amount of material available to replace clinker. We are talking about huge volumes: current worldwide cement production is around 4 billion tonnes.
As part of the project we developed a kind of cement that uses calcined clay to replace clinker. The clay is heated to between 700 and 800 °C, much lower than the temperature needed to make clinker. The lower temperatures involved and its chemical composition result in lower CO2-emissions.
Vast quantities of clay are available. The kind of clay you need contains the mineral kaolin which is widely available, particularly in developing countries in equatorial and subtropical regions of the world, for example in Southeast Asia as well as in large parts of Africa and Latin America. On mining sites, clay is often discarded as waste because it’s not good enough for purposes such as pottery or as an addition to paper to whiten it. But this waste clay can be re-used and mixed with clinker to make cement.
What’s so innovative about LC3?
Calcined clay has been used for some time now. The innovation lies in the two-part substitution: about half of the substitution for clinker consists of calcined clay, and half consists of limestone. Limestone is even more beneficial because it’s cheap and widely available. With this substitution we can go to a really low clinker content. This combination led to the name limestone calcined clay cement or LC3. It took about five or six years to come up with this two-part substitution.
Now we want to encourage the cement industry to adopt it, since doing so would have a significant impact on CO2 emissions. If cement and concrete producers around the world used this technology, it would be possible to reduce CO2-emission by more than 400 million tonnes per year. That’s roughly 1% of all the CO2 emissions in the world – or, to put it another way, about the same amount of CO2 emissions produced by a large European country, such as for France or Germany.
Why is the EPFL LC3 project leader and how is the collaboration with the Swiss Agency for Development and Cooperation?
This work was the result of research projects we had with Cuba. We had two of them which were financed by the Swiss National Science Foundation and the SDC. Since we were already involved with the SDC in this research, we went to speak with them and presented our new product to them. They encouraged us to apply for funding under the Global Climate Change Programme.
Can you explain why the geographical focus is on India and Cuba?
We worked with Cuba because that’s where we came up with the original idea. When we wanted to expand, India was the obvious place to look, because India is the world’s second biggest producer of cement after China. Even more importantly it’s in the very early stages of the growth cycle. The amount of cement used in China has grown incredibly over the last 10 to 20 years and now China produces about 60% of the world’s cement. India, which has roughly the same size as China, produces just one sixth the amount of cement. Over the next 20 years, India’s cement production will probably grow much as China’s did. They’ll need a lot more cement. That’s where this new technology can have the most impact.
What phase is the team currently working on?
We are coming to the end of the first three-year phase in our programme with the SDC. We are currently preparing for the second three-year phase.
In the first phase we worked a lot on feasibility and tried to figure out how the material behaved and whether or not it was durable. We also informed the cement industry about the technology.
We undertook multiple trials, for example on the northwest coast of Cuba, where cement blocks were exposed to rough weather conditions. We also have produced 150 tonnes of LC3 of in India. We have several demonstration projects there, for example a house built all of LC3. The new cement was used in the blocks for the new annex at the Swiss embassy in India.
We hope to secure funding for the second phase, during which we will focus on expanding awareness of our products in academia, industry and among policymakers in other countries.