Roman concrete has lasted a long time, and it may even be more powerful than modern-day concrete.
The reason? Seawater, according to a University of Utah geologist.
Marie Jackson, recently discovered that seawater helped the Roman building material last longer because it connects minerals together, giving it a stronger binding than modern concrete, according to a university press release.
Jackson and a team of researchers looked into Roman concrete to see why it held together.
To make concrete, Romans burned limestone to create lime, which is a key component in mortar. Roman builders then mixed the lime with volcanic ash from the Gulf of Naples and mixed it with salt water, according to NBC.
This mix of ash, water and quicklime created a "pozzolanic reaction," which is named after Pozzuoli, a city in the Bay of Naples, that naturally bonds the material, NBC reported.
According to the U. press release, the idea stemmed from naturally cemented volcanic ash deposits (which is called "tuff") that is common in the area.
Modern concrete is fairly similar, according to UPI. But there's one major difference: newer concrete won't have a reaction inside the mortar. If it does react with mortar, it can crack or expand, UPI reported.
“We’re looking at a system that thrives in open chemical exchange with seawater,” Jackson said in a statement. “No one has produced tobermorite (an exceptionally rare mineral) at 20 degrees Celsius. Oh — except the Romans!”
Jackson’s team of researchers found that seawater dissolved components of volcanic ash in the concrete, allowing new minerals to grow and replace what had been washed away.
And when they grew, they formed a more cohesive bond.
“We’re looking at a system that’s contrary to everything one would not want in cement-based concrete,” she says. “We’re looking at a system that thrives in open chemical exchange with seawater.”
Jackson said the recipe for such a building plan has been lost. She’s working with geological engineer Tom Adams to figure out a replacement, which would use modern minerals. They will use seawater from California, according to the press release.
Jackson said Romans took careful consideration into how they built their structures.
“Romans were fortunate in the type of rock they had to work with,” she said. “They observed that volcanic ash grew cements to produce the tuff (the name of the Roman concrete). We don’t have those rocks in a lot of the world, so there would have to be substitutions made.”
She added, “The Romans were concerned with this. If we’re going to build in the sea, we should be concerned with it, too.”
Jackson's previous research includes investigations in mineralogy, volcanism and the durability of structures. She also has worked to produce innovative and environmentally friendly masonry products and nuclear waste storage materials.
Jackson also recently weighed in on a proposal from Swansea, United Kingdom, to use a tidal lagoon to harness power. She said it would take 120 years to earn back the costs needed to build such a lagoon, according to BBC.