Concrete 2.0

29 / 10 / 21 - 8 minute read

Werner Sobek believes it is past time that we become concrete about concrete, one of the leading contributors to global carbon emissions. This internationally renowned architect and structural engineer has a solution. To ensure this 2,000-year-old building material meets the demands of a low-carbon society.

estatements: Werner, we cancelled the interview the last time we spoke as you had just received an important phone call. I hope it was good news.

Sobek: Yes, thank you. It was positive as our patent application

Sobek: Because we don’t have an energy problem, we have an emissions problem. If a carmaker wants to introduce a new car, European legislation asks them to show that the vehicle does not emit more than 95 grams of CO2 per kilometre. They don’t ask you to limit fuel consumption. In the building industry, they ask you to limit fuel consumption, that is heating energy.

Many politicians (supported by some scientists) believe limiting energy consumption for heating and warm water will reduce CO2 emissions. This is true in a certain sense. But it does not paint the full picture. My critique is the movement of energy efficiency covers only the ‘use’ phase of the building. It does not focus on the ‘production’ phase. And it does not focus on the ‘end of life’ phase.

If you look at the distribution of a building’s emissions over its lifetime, you will find that a new building emits 50% of its emissions in the erection phase, about 40% in the use phase and approximately 10% in the end of life phase (depending on the size of the building and the materials there can be minor variations of these figures). But currently policymakers only address the use phase. Moreover, they don’t take into consideration the timing of emissions. My research shows that with emissions, the production phase is dramatically more damaging to our climate than the use phase – about eight to 12 times higher! This is because the emissions related to the production phase are basically released all at once, whereas emissions of the use phase are produced over a much longer period.

To go back to today’s topic, how can we make concrete more environmentally friendly? What would concrete 2.0 look like?

There are three technologies that can be applied. The first is what I call graded concrete, which is the basis of the patent we just talked about. Here we deliberately shape the inner structure of concrete elements to reduce their weight. I have invented hollow bodies made from concrete with a very thin wall. These hollow bodies allow us to reduce the deadweight of a structure by 50% and more.

Why is concrete such a pollutant?

The chief culprit is cement, which is made by heating limestone and other materials such as clay in a kiln to almost 1,500°C. This creates a substance called clinker that is ground into a fine powder. As limestone heats, it releases carbon dioxide and changes its molecular structure. This chemical reaction accounts for up to 70% of the emissions from cement making, with the rest coming from the energy needed to heat the kiln.

Cement may make up less than a fifth of concrete. However, almost half of concrete’s carbon emissions come from the heating process that makes clinker, which relies heavily on fossil fuels. If the cement industry were a country, it would be the fourth largest carbon dioxide emitter in the world.

estatements: So, it doesn’t lose strength, just mass?

Correct. We only take away material from inside the building components where it is not structurally needed. In the end, the interior of the building components looks like a Swiss cheese or, in technical terms, a sandwich structure.

The second technique is to use gravel and sand to make concrete, put them in containers, and then flood the containers with liquid CO2. The CO2 typically comes from biofuel production or similar. This CO2 is usually released into the atmosphere, but you can condense and liquefy it and then bathe the aggregates of the concrete with it, so they take up a lot of the CO2. In this way, it’s bound chemically in the aggregates. And once you use the aggregates to mix the concrete, the CO2 is effectively stored away for good.

The third technology needs a bit of background. If you look at the combustion ovens used for producing cement, they burn either gas or oil in the primary heater. Now it is expensive to heat up that stony material to 1500 Celsius, the temperature required to turn the raw material into clinker, the basis for concrete.

In many cases, they fire cement ovens with old tires, with industrial waste and so on to reach this temperature. The material is often so toxic that the supplier pays the cement factory to burn it.

The emissions caused by the burning of cement are composed of two groups: one is the emissions caused by the flames of the fire combusting this toxic material, and the second is the chemical reaction of the sandstone while it is turned into cement. The chemical reaction is about 50% of the emissions and is unavoidable. But the emissions caused by burning waste could be avoided completely if you heat the oven with green hydrogen.

Now, let’s step through the mathematics: cement production accounts for 8% of all climate change gases – more than the entire aviation industry. If we fire the ovens with hydrogen, we save half of the emissions, which means 4% of all global emissions. If we then take my technology of graded concrete, where we use only half of the material, we save another 2%. And if we then take the aggregates for that 2% and bathe them in liquid CO2, then it’s close to 0%. This is what I’m proposing for producing carbon-neutral concrete.

estatements; It sounds logical when you explain it. However, one of the pushbacks you always hear from the business side regarding sustainability is expense. How would this stack up in terms of costs?

Yes, expense is often the overriding consideration, but the real estate industry will soon be running into the reality that the European Union and many other countries are underwriting a reduction in emissions of 50% in the upcoming ten years. If they adhere to this, then under the current processes, by the early 2030s you will not be able to build anything anymore – at least not the way we have been doing over the last 100 years. OK, there may be loopholes where people buy certificates for CO2 emissions. Still, these will come from developing countries in Africa who sell their allowances and consequently have no hope of ever becoming wealthy. Instead, these certificates will be used to build in Europe and North America. If the politicians follow the path they have outlined, this will dramatically influence industrial production, and it will dramatically influence the building industry.

You are saying that if we can get concrete emissions back to 0%, we can continue building.

Yes, exactly.

How optimistic are you that such innovative construction technology can be widely introduced?

The most important thing is the lack of general know-how. The effort of the media and politicians is insufficient to match the scale of the problem. Without the necessary background information, people cannot think about the situation we are in and the solutions needed to address our problems. The more research I do, the more outraged I am. What we face in the next twenty years is not only ‘global warming.’ This catchphrase is too nice a term for what is about to happen. It implies you don’t have to wear a coat outside anymore.

Rather the effect will be to create more and more areas that experience over-temperature phases. Take a place like southern Germany. Typically, in the summer, we have average temperatures of 25 to 27 degrees Celsius, and a few days with 33-34. But if the amount of these extremely hot days increases from four days with 34 degrees to eight days with 38, this will cause a dramatic reduction in food production. There’s plenty of research demonstrating that, for example, corn production will reduce by 20 to 40% if you have five, six or seven overheating days - because the plants are damaged and will not recover. If you have a reduction in worldwide food production of 20% to 40%, that means no food for up to 40% of the planet’s inhabitants. This is a simple calculation.

The Pantheon

For 2,000 years, the Pantheon has withstood weather, earthquakes and the onslaught of Barbarian invasions. It remains the largest unsupported concrete dome in the world (142 feet/43 metres high). One of the secrets to it longevity is the blend of volcanic ash and limestone used in the mortar. It is likely to remain standing long after many modern buildings where concrete made with reinforced steel (rebar) eventually corrodes and expands inside the concrete, which can cause the concrete to deteriorate.

estatements: That’s a bleak future you are painting.

We face not only thousands, but billions of people dying because of hunger. This is a clear fact. All the people dealing with that, the scientists and politicians, they know that. But they don’t speak out because the tendency is to shoot the messenger. It has happened to me. People have stood up and told me that I’m a pessimist, that I’m emphasising negative stories and so on. It is very difficult to state the truth without being smeared or portrayed as a whistle blower. However, I have been talking about this topic for 20 years. Now I am more or less permanently invited to discuss it because everyone realises that we are facing a huge problem and that there are no tools and no recipes available to address it.

Let’s try and end on a positive note. When will we see one potential tool, your concrete 2.0, in action?

Next year we hope to be involved in constructing two buildings in the dock area of Hamburg. One will be worth €40 million and the next €60 million. We will be pouring the first slabs in September (2021) to do further testing before it is implemented in the buildings next year. We are very optimistic about the outcome.

Werner, again, thank you very much for your time.

And you for yours.

Werner Sobek

Werner Sobek, through his company, has been involved in many prestigious architectural projects, including The Lakhta Center, the highest building in Europe, the National Museum of Qatar, the Shanghai International Financial Center, the Adidas World of Sports and the Ethiad Museum in Dubai. Werner is an Emeritus Professor at the University of Stuttgart, founder of the Institute for Lightweight Structures and Conceptual Design (ILEK) and an initiator of the German Sustainable Building Council (DGNB). He has always focused on the question of how to build more using less material and producing less emissions.