“I don’t remember. It must have been in 2015 or around that time”, says Harald Justnes, who is a Chief Research Scientist at SINTEF.
“There are many stories about how it all happened – that the idea even came to me at a party. But that wouldn’t be true”, he says.
Justnes is speaking about his very own Eureka moment, when a light bulb went off in his head, turning his professional world of cement and concrete, as well as his career as a research scientist, upside down. Not only that, but also his perception of what concrete can be made of.
You might think that aviation is one of the biggest beasts among the sources of emissions causing global warming and acidification. But this is only partly true. While it is true that aviation accounts for two per cent of global greenhouse gas (GHG) emissions, concrete accounts for something between five and eight percent, more than the total biomass living on the planet.
Not least to blame is the sheer volume of concrete all around us. Concrete is everywhere, in all shapes and sizes. Imagine if you will a block of concrete covering one square kilometre and rising ten kilometres into the sky – a volume of concrete equivalent to that of Mount Everest added to the planet each and every year. This has made the cement industry into the third most prolific generator of GHGs on the planet.
But today, the world can thank Harald Justnes, who was thinking of nothing in particular as he walked home from work one summer’s day in in 2015 when suddenly a light bulb went on in his head.
Chief Research Scientist Harald Justnes asked himself a question that resulted in what was virtually a religious experience. Today, his Eureka moment has turned our approach to concrete manufacture completely on its head. Photo: Tone Anita Østnor
A stupid question
Let’s return to the summer of 2015. Harald Justnes is a Professor at NTNU’s Faculty of Materials Technology, and a Chief Research Scientist at the SINTEF division Building and Infrastructure. He is attending a meeting on the NTNU campus at Gløshaugen in Trondheim all about graphene, the thinnest and strongest material that has ever been manufactured. As soon as the meeting ends, Justnes is on his way out of the door and starts chatting with a colleague working with aluminium.
Little passes between them – only that it might be an idea to use aluminium instead of steel to reinforce concrete. A simple and almost trivial suggestion, really. But mostly a stupid one, especially for a chemist like Justnes. He dismisses the idea quite quickly, almost as a knee-jerk response.
And he has good reason. Concrete is basic in composition, with a pH of between 12.5 and 13. This high pH protects the reinforcing steel from rusting – at least for a given number of years. But sooner or later, of course, the reinforcement starts to rust. Concrete constructions can last for fifty, or up to a maximum of a hundred, years before they have to be demolished and rebuilt.
“The rusting process is the Achilles heel in concrete constructions”, says Justnes.
For instance, let’s look at a typical Norwegian parking basement. Cars move in and out, loaded with slush and salt from the roads. When the slush melts, everything permeates into the concrete.
“Salt is pumped into the concrete as part of a wetting-drying cycle much faster than you might think”, says Justnes.
This doesn’t mean that the construction will collapse immediately, but sooner or later something has to be done. One option is to apply cathodic protection by running an electrical current through the reinforcing steel.
“But this is an expensive process”, says Justnes. “The best and cheapest approach is to build the structure properly from the ground up”, he says.
So, what about aluminium? Well, this isn’t really very promising. Aluminium’s worst enemy is the concrete’s high pH. It can remain stable in environments with a pH of up to 9, but then the metal really begins to suffer.
The Norwegian alternative
So, with all this in mind, Justnes dismisses the whole idea and starts walking home in the direction of Persaunet, three kilometres north-east of Gløshaugen. While allowing his mind to wander, a new question arises, like a goods train passing in the night. Justnes recalls:
“Why not make a concrete with a lower pH? Asking myself this question brought about a virtually religious experience. The rest of my walk home continued on autopilot”, he says.
The further Justnes walks, the more he starts thinking about blue clay. What about throwing more clay into the equation? Because blue clay offers some clear benefits. First of all, you only have to heat it to 800 degrees. Cement clinker, which is made up of 80 percent limestone, requires 1,450 degrees. When the limestone decomposes, 60 percent of the total emissions are CO2. The remainder comes from the fuel used to heat the process.
As well as much lower energy consumption, blue clay has another advantage. It declines to take part in the entire CO2 equation for the simple reason that we can use biofuels, which emit net zero CO2 during combustion.
Aluminium tolerates both CO2 and chlorides. This gives it an infinite lifetime when compared to steel – hundreds, perhaps up to a thousand years.
Harald Justnes
But, and there is always a ‘but’.
Norwegian blue clay consists of a mixture of the minerals kaolin, illite and smectite, as well as crystalline quartz. Illite is blue clay’s Achilles heel. It is a grey, silvery mineral, also known as hydromica. Both illite and smectite have a reputation for being difficult to utilise in chemical processes.
Nevertheless, as he walks home, Justnes thinks that it might just be worth a try. In fact, his idea about blue clay did not come entirely out of the blue. Kaolin, which is also known as china clay, is used in the manufacture of porcelain, but is not very common here in Norway.
– By the way, what was the weather like that day?
“I don’t remember”, replies Justnes. It might have been snowing for all I know. But in my head the sun was shining and the birds were singing”, he says.
Concrete is the most utilised building material in the world and one of the worst sources of greenhouse gas emissions. Here we see some colourful concrete brightening up residential buildings in Genoa in Italy. Photo: Øystein Lie
The mysteries of concrete
Concrete has a long and complicated history, so here is a simplified version. Concrete cannot be concrete without cement. The cement serves as the ‘glue’ that holds the aggregate of sand and gravel together.
When the cement reacts with water, the entire aggregate solidifies. This technique has been used by human civilisations for three thousand years, perhaps even longer, although different binding materials have been used through the ages. In practice, they used whatever they had to hand. What we do know is that the ancient Egyptians used gypsum as a binding material when they built the pyramids.
This was in spite of the fact that gypsum dissolves in water, but then it didn’t rain very much in that part of the world. The Greeks and Romans combusted lime, and extracted a powder that solidified with the help of water and CO2.
“The Romans mixed ash from the Vesuvius volcano and found that this made the concrete much harder”, says Justnes.
It wasn’t until the 1800s when the British found out that it was possible to combust clay and lime together to make cement. After that, some smart people realised that it was useful to add reinforcement to the concrete, especially for bigger and taller buildings.
Concrete can withstand high pressures, but has a relatively low tensile strength. In fact, concrete’s tensile strength is only about one tenth of its compressive strength. This is why we use steel to reinforce concrete.
The big question in Justnes’ mind on this summer’s day nearly ten years ago was whether the days of steel were over. Perhaps it might really be possible to manufacture a ‘greener’ concrete? Could this be the beginning of the age of aluminium in the construction sector?
Cement and coffee
The day after he walked home, thinking of nothing in particular before his Eureka moment, Justnes was back at work. He didn’t waste any time. The first thing he did was to fetch three cups. The first he filled with cement and water. The second also contained cement, but made up of 55 percent burnt blue clay. The third, and perhaps the most important, was a cup of coffee for himself.
Then he dipped a fragment of aluminium into each of the first two cups and took a good look. In the first cup containing ordinary cement, hydrogen gas was bubbling from the metal. This is exactly what he expected. The aluminium didn’t like the high pH.
“But nothing was happening in the other cup”, says Justnes.
A quite sensational non-event.
“I took photos of the two cups, and immediately arranged a meeting with the company Hydro.
After seven years of discussions, which in all fairness Justnes calls research and, true enough, without PhD student funding because of the highly uncertain outcome and benefits linked to the project, you will now find a small bridge across the river Grødøla in Sunndal, completed only last summer.
At first glance, it doesn’t look like anything special. Barely twenty, and certainly no more than thirty, metres long, with its weight supported by four concrete piles. The new concrete forms the upper part of the bridge, with aluminium below. There is a little aluminium on the top as well, for aesthetic reasons. It would be unthinkable to have a steel structure exposed to the elements in this way. It is nothing short of sensational!
“Aluminium tolerates both CO2 and chlorides”, says Justnes. “This gives it an infinite lifetime when compared to steel – hundreds, perhaps up to a thousand years”, he estimates.
Blue clay is very common. You just have to dig it up and feed it to the kiln A further advantage of using clay is that the concrete doesn’t need to be as massive as in the past to prevent CO2 and chlorides from penetrating to the reinforcement.
And less concrete mass means fewer GHG emissions. Overall, we are left with locally-sourced blue clay containing pozzolan, which only needs to be dug up and heated to temperatures as low as 800 degrees, instead of the 1,450 degrees required by clinker. Then, add in the aluminium, which requires only half as much heat as steel, and the total CO2 emissions from concrete manufacture are dramatically reduced by anything between 60 and 80 percent.
And we can boost this even more by taking into account a more or less infinite lifetime with no maintenance requirements.
However, there are many other researchers who are in the process of making the global concrete industry more eco-friendly, and one of the key actors here also works for SINTEF.
Key facts
The first-ever skyscraper was built in Chicago at the end of the 19th century – the result of a coming together of capitalism and the steel industry.
The first skyscraper, called the Home Insurance Building, was built in 1885 and originally ten storeys tall. Two storeys were later added, raising it to 55 metres above ground level.
Today, such a building would be regarded as almost tiny, and hardly worth talking about. These days a building must be more than 150 metres high before it can be called a skyscraper.
At the time of writing, and according to the Council on Tall Buildings and Urban Habitat (CTBUH), a building has to be taller than 338 metres before it gets onto the list of the hundred tallest buildings in the world.
No excuses for not knowing the name of the world’s tallest building! It’s always turning up in pub quizzes – the Burj Khalifa in Dubai. When it was finished in 2010, it was 828 metres tall.
Source: snl.no and skyscapercenter.com
The art of replacing coal
It is one thing to talk about blue clay, pH reduction, the use of aluminium, a chemical process running at half the temperature and everything else that Justnes has been working to achieve. But there is always more that can be done. Of course there is! If concrete is to be made even more eco-friendly, there is yet another factor that has to be taken into account. This is energy.
Energy is the field of SINTEF researcher Kåre Helge Karstensen. He doesn’t work in a lab like Justnes, but out in the field and often very far from Norway.
“Humans have been using coal for thousands of years”, says Karstensen, who is also a Chief Research Scientist at SINTEF.
“In 1972 we witnessed the first major oil crisis”, he says. “When the oil price sky-rocketed because of political factors, the cement industry in the USA started to replace fossils fuels by combusting waste that had to be processed anyway. This is what so-called co-processing is all about”, says Karstensen.
Since the mid-1980s, Karstensen has been working in a hundred countries to promote the use and facilitation of co-processing technologies. He got the ball rolling here in Norway at Norcem, the country’s only cement manufacturers. Starting from scratch, Norcem started to feed everything from paper, forestry waste, poultry bones and plastics into a high-temperature cement kiln.
The kiln was also fed with hazardous waste, as well as coating materials, oils, paints and other chemicals. This was pioneering work that has now borne fruit. Today, the situation here in Norway is that the cement industry has replaced more than 75 percent of the coal it used to combust with waste.
“This is a win-win situation both for the cement industry and wider society – in fact for pretty much everyone”, says Karstensen about co-processing.
Karstensen is also the man that experts talk about when looking to use high-temperature cement kilns as a means of getting rid of hazardous waste and chemicals.
We’re now in the process of compiling a final report after a 14-year project in India, where on average they have replaced three percent of coal with waste. Do you comprehend what I’m saying? Do you see the potential?
Kåre Helge Karstensen
Last year, Karstensen was asked to serve as a consultant to the Technical Advisory Group linked to the UN Environment Programme, whose aim is to advise on how the world can achieve zero emissions by 2050. This is something of an uphill task, but there is always hope.
“When, in 2006, we launched a twelve-year project in China, the country had only a single cement factory that utilised waste as fuel in addition to coal. Today, hundreds of cement factories are operating with co-processing technologies, and the approach has become a principal strategy in Chinese waste management policy”, says Karstensen.
The same thing is happening in India, and this is good for the environment. Together, China and India are responsible for more than half of the cement manufactured on the planet.
“We’re now in the process of compiling a final report after a 14-year project in India, where on average they have replaced three percent of coal with waste. Do you comprehend what I’m saying? Do you see the potential?
Karstensen is ready with the answer to his own question.
“India produces hundreds of millions of tonnes of waste, but has barely begun to exploit the opportunity offered by the cement industry”, says Karstensen. “When we started in China, only 0.1 percent of waste was being utilised – virtually nothing at all. I don’t have the latest figures for coal replacement in China, but Europe is averaging 50 percent”, he says.
And, according to Karstensen, one thing is certain.
“China and India are right on our heels”, he says. “Some of the most ambitious cement manufacturers in India are aiming to be carbon negative as early as 2035 or 2040. Government policy is that the entire country will be carbon neutral in 2070”, says Karstensen.
But this won’t happen overnight. One reason is the economic cost. Innovative thinking is also a factor.
And then there is the jungle of legislation and regulations that have to be adhered to. However, Karstensen must do what he can to influence the outcome. In practice, this means working closely with governments, the UN system, the World Bank and, not least, the cement industry, to convince them all of the opportunities inherent in boosting waste management capacity and at the same time reducing CO2 emissions.
What about all that plastic, then?
Eco-friendly concrete uses blue clay as a key ingredient. Blue clay is very common, even on Norwegian beaches. This photo is taken from Hitra in Trøndelag. Photo: Øystein Lie
The problem of plastics
OK, here are some figures that will make your jaw drop to the floor. In the last 70 years, humans have achieved the master stroke of generating 6.3 billion tonnes of plastic waste. Nine percent of this has been recycled, while 12 percent has been used as fuel. The remainder has been dumped either in landfill or, even worse, directly into the oceans.
As part of a pilot project in Vietnam, Karstensen and his colleagues at SINTEF found out that the combustion of non-recyclable plastic waste was not the environmental catastrophe that many had expected. Dioxins, which are toxic to humans and other animals, are in fact not generated when these plastics are combusted in a high-temperature cement kiln. This means that such combustion processes are in full compliance with global emission limits.
And in some places, there is no time to lose.
“In Thailand there are as many as 2,500 so-called ‘dump sites’, which are essentially landfills containing in total 200 million tonnes of plastics”, says Karstensen. “These plastics are gradually being broken down into microplastic particles which will permeate first into the groundwater, then into the rivers and eventually out to sea”, he says.
According to Karstensen, this will be our future unless we tackle these issues without delay.
Combating opposition to change is part of Karstensen’s job.
“Obviously, you will always encounter people who are simply out to feather their own nests”, he says. “We meet a lot of opposition to our proposals simply because the solutions appear to be too good to be true. And in some ways, they are! Very straightforward and almost ingenious if you implement them properly”, says Karstensen.
Stupid questions
Harald Justnes will be 69 this autumn. At SINTEF he can keep on working until he is 72. There have been pats on the back, bouquets of flowers and SINTEF’s prize for outstanding research.
Just for the record, Justnes’ colleague Tobias Danner was also awarded a prize for creating the recipe for a more eco-friendly concrete – containing calcined clay as a substitute for cement.
With his PhD in catalysis, Justnes started working with concrete in 1985.
“I didn’t know the first thing about cement”, he says. “To me it was just a grey powder that solidified when you mixed it with water. I had no idea about what the issues were. But I got the job. Most people in the field of concrete hated ‘chemistry’, but I read all the books I could lay my hands on”, says Justnes.
“I asked myself all the stupid questions and I now realise that it was in fact an advantage not to have any education in the field”, he says.
