The amount of concrete poured into a pile wall as part of the vast Transpennine Route Upgrade was not particularly impressive. Over 12 weeks, about 150 cubic metres was due to be poured – a tiny fraction of the 22 million cubic metres used across the UK every year, according to trade body the Mineral Products Association.
But the concrete used in the capping beam at Shipley Depot in West Yorkshire was more unusual for what was missing. The material used Ecocem’s Act cement technology, which substantially reduces the amount of clinker required, the carbon-intensive ingredient at the heart of conventional cement. Construction company Murphy Group, which is doing the work with Breedon and Ecocem, says it was the first time Act has been used in a permanent works project in the UK.
“This latest pour is both an example of innovation utilised for the good of the engineering industry, and a further demonstration of our commitment to creating a greener Murphy, becoming net positive by 2050,” said Kyle Stott, engineering manager at Murphy.
The work has implications beyond Murphy, offering an opportunity for the entire construction industry to help in the battle to decarbonise. About four billion tonnes of cement are produced globally every year, making it the most widely manufactured material on Earth after clean water. Researchers at the University of Leeds put cement's share of global carbon dioxide (CO₂) emissions at about 8%.
“Because there are four billion tonnes of cement produced every year, just shaving a couple of percent off the emissions per tonne can have a significant impact,” said Leon Black, professor of infrastructure materials at Leeds, who researches low-carbon cement.
The problem is that much of cement’s carbon footprint is from its chemistry. Just over half of conventional cement's emissions come from breaking down calcium carbonate in the kiln, according to Black. Roughly 40% comes from the fuel needed to heat it, with the remainder associated with processing.
Alternative fuels, more efficient kilns and cleaner energy can tackle part of that. But reducing the amount of limestone that has to be turned into clinker in the first place is where the biggest gains can be had.
For decades, cement producers have blended clinker with materials such as fly ash from coal-fired power stations and ground granulated blast furnace slag from steelmaking. “As we’ve decarbonised electricity, that’s no longer available,” Black said of fly ash. Steelmaking is changing too, with the growth of electric arc furnaces producing a different form of slag that cannot be swapped in for blast furnace slag in cement.
That has pushed researchers to test alternative materials, among the most promising of which is calcined clay. Rather than heating clinker to about 1,400°C, clay can be activated at roughly 800°C, making its carbon footprint only 100-300kg per tonne, compared with about 840kg for conventional cement.
Calcined clay is not a silver bullet, and could only replace 20-30% of cement on its own. But combine it with limestone and replacement rates of about 50% become possible, Black said, with carbon reductions of 35-40%.
Those advantages come with some new challenges. Changing cement chemistry can change its setting time, flow and workability. Calcined clay mixes are generally stiffer and set more quickly, for instance. Differences like those become more challenging when put into production processes and onto building sites.
“A contractor doesn't want to have any change,” Black said. “They want to be able to keep pouring concrete, just as they've been doing for many, many years.”
Ecocem’s Act uses only about 20-30% clinker, replacing much of the rest with limestone and supplementary materials used in cement while being designed to work with existing plants and construction practices. At Shipley, Murphy expects a saving of 145kg carbon dioxide equivalent per cubic metre against its benchmark concrete mix. A new Act production facility under construction in Dunkirk is expected to have capacity for 300,000 tonnes a year when fully operational at the end of 2026.
Clinker substitution is not the only technology leaving the lab. Heidelberg Materials opened the world's first industrial-scale carbon capture facility at a cement plant in Brevik, Norway, in 2025, designed to capture about 400,000 tonnes of CO₂ annually – about half of the plant's emissions – for permanent storage beneath the North Sea. Marley’s new Edgemere 2.0 concrete roof tile uses locally produced Heidelberg cement, while verified emissions reductions from Brevik are allocated to the product through an environmental attribute certificate, rather than shipping Norwegian cement to Britain.
Neither approach is likely to solve cement's carbon problem alone. Reducing clinker can remove emissions before they occur; carbon capture offers a way of dealing with the emissions that remain when clinker is still required. But it is becoming increasingly possible to make those changes without asking contractors to radically change how they work. “Yes, there are issues at the moment, but within the next few years, those issues will diminish,” said Black.
Extracted from IMechE website, read more here