Rock stars: the academics answering the construction sector’s hardest question

Our assistant editor talks to the PhD students on a mission to crack low carbon cement.
Image by Oliver Ulerich
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“The Eureka moment doesn’t exist. At most, you get an accidental success”, says Barney Shanks, Chief Technical Officer of new start up Seratech which he co-founded with CEO Sam Draper. As PhD students who sat beside each other in the labs, they realised that combining their research could help solve a problem with which the whole world is wrestling: how to get production emissions from concrete down to zero? And Urban development is synonymous with concrete.

When God created the world in six days, he probably could have got it down to three (and at a fraction of the cost) if he’d used concrete. Yes, bio-based materials like wood and straw – hemp included – are becoming more serious tools in the architect’s arsenal, but they’re still not concrete. And Cement is to concrete as milk is to ice cream, with no oat alternative. The big question for the construction sector then, is how can we decarbonise cement? Cement is cheap, it’s fast, you can pour it into any shape you like, and it’s available everywhere. A trendy statistic from urban studies is that the material equivalent of an entire New York City needs to be built every month for the next 40 years to meet current trends. Try telling a government in the Global South that they have to meet the demands of population growth without concrete. Try telling a government in the Global North that they have to meet the demands of population growth without concrete.

The standard cement-making process breaks down limestone (calcium carbonate) into calcium oxide and CO2. Concrete suppliers are experimenting with substituting part of the limestone component with slag, a low value by-product of steel production. Cement plants in the UK currently import slag from mainland Europe to hit decarbonisation targets. If this is raising eyebrows over transport emissions, it probably should. Another hackneyed stat: if the cement industry were a country, it would currently be the third largest emitter in the world.

But innovation in the field is growing. Canada-based Carbicrete, for example, combines low carbon-concrete with carbon capture and storage (CCS) technology. They replace a percentage of the cement in concrete with steel slag. Carbicrete’s product comes as pre-cast cement blocks which are through CO2 injection, sequestering CO2 from the atmosphere. This has limitations: the product’s longevity is in question, and steel production is itself currently a carbon intensive process. With most countries’ decarbonisation agendas including plans for massively increasing the recycling rates of steel, slag supplies will become limited. And pre-cast cement blocks also further raise construction and design issues; one of cement’s advantages is that it can be poured into any shape.

"People aren't taught to think about things like colour in academia."

Seratech’s innovation is to claim to offer a cement-making process which involves CCS, makes workable cement, and does not emit CO2 in the process. Almost two years ago, Barney was looking into the chemistry of silica-based cements. Beside him, Sam was working on limestone replacement in cement systems. One day Sam turned to Barney and said, “Would that silica work in a normal cement system? And Barney said, “I don’t see why not.” They looked at the clock, saw it was gone midnight and went to the pub to talk.

Seratech’s carbon neutral concrete is not photogenic. Right now, it is a grey powder in a zip-loc bag in Imperial College, London. Their process works by taking CO2 from a cement kiln or flu gas stream, and combining the CO2 with olivine, a magnesium iron silicate. This forms silica and carbonate – crucially CO3, not CO2 – and the silica can then be used as an additive to cement. Currently, they are working on a basis of mixing cement with 35% of their own additive, and 65% traditional Portland cement. There’s potential to scale up the amount of additive used, meaning their product would not just be zero carbon, but carbon negative. As we look towards a circular economy, the carbonate could also be returned to the supply chain and used in construction or agriculture projects. They cannot say too much about the applications of the carbon as they are looking to patent these uses.

Imperial College’s engineering faculty is a peculiar place. While we are talking, a young man in an attitude of total distress sprints across the room, bearing a Dell laptop aloft and furiously pressing the backspace.“We’re both very, very sad people.” Sam says, shaking his head. “We like science. Well, you like science” nodding towards Barney, “I like concrete…more than either of us actually should.” Photogenic or not, Seratech could be an answer to a sustainable development dilemma.

Like many business partnerships, Barney and Sam come at the problem from different angles. “I’m a sucker for science generally”, Barney says. “I’ve downloaded a biology textbook on Audible and I’ve listened to 70 hours of it. I just like having a solid understanding of the natural world and stuff that’s going on around you.” Sam is eyeing him sideways. “Yeah. I have a much less romantic view of it. I would be a terrible academic. I can’t do science for the sake of science. For me it has to be, relentlessly, “How can we translate this into the actual world? But I like exposed concrete faces. Brutalism. Funnily enough, the guy who loves concrete loves concrete.”

There’s a neatness to their partnership. They’re aware of what the other knows more about. “It’s more like we’re aware of what we don’t know.” Barney says. “So he has to know the stuff that I don’t.” Neat.

But none of the innovators is looking to “break the mould”. Disruptive technologies can’t be too disruptive. The cement that arrives on site has to look and behave just like the traditional stuff. To fit any mould. In Barney and Sam’s initial trials, their concrete test blocks were coming out purple. “People aren’t taught to think about things like colour in academia.” Barney says. ‘But when we go and speak to designers and architects, one of their first questions is “What’s it going to look like?” That’s the kind of thing people actually care about.’

If decarbonising concrete were easy, the cement industry valued at $313.6billion in 2020 would have done it by now. Three months into Sam and Barney’s joint venture, their trials yielded little. “It’s the hope that kills you.” “I did throw a chair across the room once.” Sam says. “Surface area.” They shudder. But then, four months into their experiments, the material started exhibiting excellent properties. “Until then we’d been playing around.” Barney said. “That was the moment for me when it went from a bit of fun to, like, we have to take this seriously now. We have to make it work.”

“Does that feel emotional, then?”


There will come a point when cement companies will have net zero targets to reach. And many have argued that point should have come many years ago. (Cement companies are still given free emissions allowances under the EU Emissions Trading System, for example, which was first launched in 2005).

Carbon capture facilities are hugely expensive, around £200 per tonne of cement produced. In 2021, cement production was at 4.4billion tonnes worldwide. Let’s imagine there were enough CCS facilities to capture and store all that carbon – that would run into the hundreds of billions. It is in the cement giants’ interests to listen to people like Barney and Sam. They project that if the whole cement industry moved to their additive, three gigatonnes of CO2, or about 65% of the USA’s total annual emissions, could be sequestered in a year. This would bring total global emissions down by 8%. Seratech are currently in talks with global cement plants, and have received funding for a pilot factory, their first opportunity to make their product at an industrial scale. Barney seems unconcerned. “It’s just bigger buckets.” Sam chuckles. “Optimistic.”

Lauren is an Assistant Editor at LCR. Her work has focused on geopolitics & climate policy, emissions solutions in the buildings sector, and reviews of new environment titles. Find her LinkedIn here, or email her at

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