2000-year-old Roman engineering could solve colossal climate problem

As the saying goes, all roads lead to Rome. And as the construction industry grapples with concrete’s climate problem, some engineers think a technology dating back to Roman times might hold the answer.

Durability engineer Miles Dacre from consultancy AECOM, speaking at the Climate Smart Engineering conference in Melbourne, says emissions associated with concrete are increasingly under the spotlight. 

Dacre works on major infrastructure projects, which generally involve a lot of concrete. 

Demand for concrete has doubled in the last 20 years, he says. “It’s our number one building material that our whole civilisation requires to function the way it does,” Dacre says. 

But concrete accounts for about 5-8% of global greenhouse gas emissions, according to the Rocky Mountain Institute, and a key contributor to those emissions is cement. Producing cement involves heating limestone, a process that releases greenhouse gas emissions directly, as well as indirectly from burning fossil fuels to heat the kiln. 

Dacre offers a low carbon alternative to traditional Portland cement called calcined clay: “ probably the same concrete that the Romans used … going back 2000 years”.

“We need to change to that material as quickly as possible,” he says.

Recently a paper published in Applied Clay Science argued that environmental and emissions problems can be minimised by switching to the ancient Roman concrete. 

Calcined clay is made with a blend of clinker, calcined clay (a heat treated clay), limestone and gypsum.

“In addition to the environmental considerations, Roman concrete also represents the epitome of extremely durable cement-based materials,” the paper says. “Roman concrete exposed to harsh maritime environments remains in a remarkable condition even 2000 years after construction, while modern ordinary Portland cement concrete shows degradation within 32 weeks of exposure to seawater,” the authors write.

Dacre says anyone working in the engineering and construction industry who doesn’t know about calcined clay needs to educate themselves. The cement alternative has the potential to reduce emissions by roughly 40% compared to ordinary Portland cement. 

“We’ve just got to prove it as quickly as possible; it’s going to take everyone in the engineering business to do that.” 

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