Tough stuff – that suits her. Karen Scrivener is a renowned expert on the world’s most widely used building materials: concrete and cement. But cement as a binding agent has fallen into disrepute as a “climate killer”. The professor disagrees. The head of the Laboratory for Building Materials at EPFL’s School of Engineering in Lausanne can point to more than just pioneering research into more energy-efficient concrete production. She also has her eye on global construction activity – and has big plans.

Karen Scrivener has been passionate about concrete for 40 years. The materials scientist is often asked how she came to be interested in concrete in the first place. “I always wanted to deal with real life. And when I was looking for a research topic, I looked around at various universities. When it came to metals, the most exciting developments were 100 years ago. A professor at Imperial College in London finally brought the subject to my attention. There was potential: it sounded interesting.”

Knowledge gaps closed

For her, it remains unbelievable that we build so much with concrete and yet know so little about it.

“It looks so simple: We mix a gray powder with water and a stable building material is ready. But complex chemical reactions take place here,” explains the scientist. Compared to the life sciences, there are still plenty of gaps in cement research.

In her long career in science and in the cement industry, Karen Scrivener has done much to close these gaps. The British researcher is working on how to improve concrete production processes with regard to the mechanical and, above all, the environmental properties of the building material. In view of the global efforts to reduce greenhouse gas emissions, this is more important than ever.

This is because the central components of concrete are cement and various aggregates such as gravel, sand, chippings or pumice. Today’s so-called Portland cement is obtained by burning limestone at very high temperatures to form clinker. This leads to high emissions in two ways: on the one hand, due to the energy input, and on the other hand, because the limestone is broken down into calcium oxide during burning. This chemical reaction is responsible for 60 percent of these emissions. However, according to Scrivener, it is technically almost impossible to completely eliminate these emissions.

Search for substitutes

One way of reducing CO2 emissions is to reduce the proportion of clinker and replace it with other materials such as fired clay. In the search for ideal substitutes, the scientist and her interdisciplinary team of around 30, together with other research and industrial partners, have made a real breakthrough with “Limestone Calcined Clay Cement”. This calcined clay can be fired at only 800 degrees Celsius instead of 1450 degrees Celsius, and does not emit CO2.

“Every year, we produce 30 billion tons of cement-based material,” released by the chemical process. LC3 technology makes concrete production cheaper, less capital-intensive and saves up to 40 percent carbon dioxide. At an estimated 400 to 800 million tons per year, the potential leverage for global CO2 reduction is enormous.

The scientist is aware that concrete is nevertheless considered by many today to be universally hostile to the environment. “But that’s wrong,” she disagrees in a firm tone. In itself, concrete has the lowest CO2 footprint per kilogram compared to all other materials. Concrete lasts a long time, so the life cycle is positive. The professor also sees the ecological problem not primarily in the building material itself, but in the gigantic quantity that is used every day. “Every year, we produce 30 billion tons of cement-based material (concrete, mortar) worldwide, which is huge and significantly more than all the other materials that humans use together”.

Concrete house with wooden floor

This unimaginable quantity – and it poses a real dilemma – demonstrates how huge the demand is worldwide.

“Stopping concrete construction is not an option for emerging economies,” says Karen Scrivener. After all, more than a billion people still live in slums today. When it comes to building new houses, concrete is cheap, easy to transport and always available – the raw materials are abundant in the earth’s crust.

Replacing concrete completely with wood is not a solution for Scrivener. Wood can supply a maximum of five to ten percent of the global demand for building materials and is not a solution for the Global South. “It’s a perfect material, but there’s just not enough area for the forest that would be needed – and we don’t have 30 years to grow enough trees either.” She herself lives in the country in a house made of concrete. “But at least it has a nice wooden deck,” she says with a laugh.

The professor advocates realistic solutions and always has her sights set on translating research into “real life”. It is no coincidence that she once turned her back on academia to work for six years in industry, at Lafarge in Lyon.

Global partnerships

“We can’t do without concrete altogether,” explains the professor, “and will have to use many different materials. In the climate debate, it’s crucial not to miss opportunities to reduce energy consumption in existing technologies by making them absolute.” For concrete, she calculates that up to 30 percent emissions could be saved at the level of cement production alone, another 20 to 30 percent in reducing the amount of cement in concrete, and as much as 50 percent in the amount of concrete used in buildings. That would be enormous progress.

The big challenge, says Karen Scrivener, is to get everyone involved in the construction process around the table – worldwide. Her major new project is a “Center for Worldwide Sustainable Construction,” which cooperates closely with industry and trains doctoral students, mainly scholarship holders from poorer countries. The aim is for them to take the latest solutions to their countries. “Such global partnerships are important because climate change affects the whole world.”

Author: Cornelia Glees

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