Roman Concrete May Be Key To Protecting Cities From Rising Sea Levels
Everybody who is not part of the Trump administration knows that rising sea levels are a danger to many of the world’s principal cities. Building barriers to keep the oceans from inundating population centers will be part of the solution, albeit a temporary one.
Sea walls and barriers built by the Romans have endured for 1,500 years — far longer than anything made with modern concrete, which relies almost exclusively on Portland cement. A group of scientists was curious about what made Roman concrete so durable. Instead of breaking down when in contact with the sea, the Roman concrete actually gets stronger with time.
After considerable research, the scientists think they have discovered the key. The Romans used a mixture of volcanic ash, lime, seawater and volcanic rock to make concrete piers, breakwaters, and harbors. They think the seawater reacts with the volcanic material to make new minerals that reinforce the concrete as it ages.
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Marie Jackson, a geologist at the University of Utah, is one of the authors of the study. She says the Romans “were very, very intelligent people. They spent a tremendous amount of work on this.” Writing in the journal American Mineralogist, Jackson says she and her colleagues analyzed samples of Roman concrete and made a new discovery.
“I went back to the concrete and found abundant tobermorite growing through the fabric of the concrete, often in association with phillipsite,” she wrote. Over time, these two minerals crystallize inside the concrete, reinforcing it and preventing any cracks from growing.
She notes the Romans were well aware of the properties of the concrete they made. No less a personage than Pliny the Elder admired rhapsodically about how Roman concrete was “impregnable to the waves and every day stronger.” Sounds like a 21st century commercial.
Regarding the potential for new versions of Roman concrete, Jackson says, “There’s many applications but further work is needed to create those mixes. We’ve started but there is a lot of fine-tuning that needs to happen. The challenge is to develop methods that use common volcanic products and that is actually what we are doing right now.”
In addition to its strength and durability, concrete made the Roman way with volcanic materials does away with the climate impacts associated with making Portland cement, the modern choice for concrete structures. ConcreteThinker says cement production accounts for about 5% of annual carbon emissions worldwide.
Rising sea levels will lead many coastal cities to invest in seawalls and other structures to ward off the advance of the tides. It makes little sense to build them out of concrete if they won’t last long enough to fulfill their purpose and if making cement contributes significantly to the process that causes rising sea levels in the first place.
Source: The Guardian | Photo by Bernard Gagnon (some rights reserved)
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