Researchers have solved the riddle of how structures built with ancient Roman concrete have survived millennia
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Spotted: The ancient Romans were master builders. While many modern concrete structures have crumbled in just a few decades, many Roman structures are still standing, including the Pantheon, which has the world’s largest unreinforced concrete dome and was completed in 128 CE. Roman concrete has been known to withstand earthquakes and harsh weather, and certain variations could even set underwater. Until now, exactly what made Roman concrete so durable has remained something of a mystery.
Now, a team of researchers from MIT, Harvard University, and laboratories in Italy and Switzerland, has discovered some of the ancient concrete-manufacturing strategies used by the Romans. They found that Roman concrete contains ‘lime clasts’ – tiny minerals originating from lime that give the concrete the ability to self-heal. Spectroscopic examination also suggested that the Romans used lime in its more reactive form – quicklime.
The researchers concluded that the process of incorporating quicklime, known as hot mixing, was key to the concrete’s durability. During hot mixing, the lime clasts develop a ‘nanoparticle architecture’. When cracked, this reacts with water to create a calcium-saturated solution, which then recrystallises as calcium carbonate and quickly fills the crack.
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Written By: Lisa Magloff