Ancient Roman Concrete Was Inspired By Volcanic Chemistry

In 1982 , the footing beneath the historic embrasure metropolis of Pozzuoli began to rise like a patty in the oven . Within two years , the swell had exceeded 6 human foot . Then the earth jump shaking — first , a horde of microquakes . When the first magnitude 4 quake hit , Pozzuoli became a touch township overnight .

Tiziana Vanorio , a geophysicist at Stanford University , was a stripling when the seemingly apocalyptic outcome force her family to flee Pozzuoli along with the urban center ’s 40,000 other residents . Now , over thirty year later , Vanorio seems to have discovered what caused the 1982 phenomenon that first spark off her interest in geology : A fibre - reinforced , concrete - like rock , form in the astuteness of the nearby supervolcano Campi Flegrei .

It gets weirder . The ‘ natural concrete ’ Vanorio regain in Campi Flegrei is similar to the fabled concrete used by the ancient Romans to construct the Pantheon , the Colosseum , and numerous merchant vessels interface throughout the Mediterranean . It ’s so much of a happenstance , Vanorio now suspects the Romans contrive their concrete after observing the instinctive chemical reactions occurring around Pozzuoli .

Pozzuoli and Campi Flegrei both lie within a caldera — a great depression pockmark by craters from previous volcanic eructation . While ground protuberance is a common plenty at calderas around the earthly concern , including Yellowstone and Long Valley in the United States , the speed and size of the 1982 fop at Pozzuoli was unprecedented .

“ It usually requires far less uplift to trigger earthquake at other places , ” Vanorio said . “ At Campi Flegrei , the micro - earthquakes were delayed by months despite really turgid ground deformations . ”

To learn why the Pozzuoli caldera was able to withstand such incredible strain without crack , Vanorio and her colleagues test rock and roll CORE collected during a 1980s drilling excursion . Within these cores , they apace place the caprock — a hard , volcanic - ash tree rock layer establish near a caldera ’s Earth’s surface — and get word that it was full of tobermorite and ettringite , two fibrous minerals also found in manmade concrete . These minerals , the researchers say , are what makes Campi Flegrei ’s caprock so darn pliable .

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What ’s more , the researchers were able to show that these concrete - like mineral shape through a serial of reactions eff as decarbonation . That ’s what happens when hot , mineral racy water interacts with limestone , forming carbon dioxide and calcium hydroxide gases . The ancient Romans might have observed a standardized decarbonation process taking place near the surface surrounding Pozzuoli , and exploited it to work their famous concrete .

“ The Romans were acute observers of the instinctive earth and hunky-dory empiricists , ” Vanorio said in astatement . “ Seneca , and before him Vitruvius , sympathise that there was something special about the ash at Pozzuoli , and the Romans used the pozzolana to create their own concrete , albeit with a dissimilar source of slaked lime . ”

Vanorio believes that the same chemical substance reaction responsible for shape the caprock at Campi Flegrei probably activate the 1982 beau . If decarbonation find too quickly , excess CO2 and steam will rise toward the surface of the caldera , heating and swelling the rock . As before long as the ground begins cracking , these pent - up gasoline air into the ambiance and the swelling subsides .

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So there you have it , folks : A 2,000 - plus class sometime mystery and a 30 year quondam mystery , solved in one fell slide with a little geology . The ways in which nature can spark innovation never cease to amaze me . But the fact that complex geochemical response might have inspired one of the most iconic edifice materials in human history….well , I guess it ’s no wonder Romans conquered the ancient world .

[ Stanford News ]

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