News (Ancient) New Research Shows How Natural Chemistry Strengthened Ancient Roman Marine Concrete

 

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While modern marine concrete structures crumble within years, ancient Roman piers and breakwaters endure to this day, and are stronger now than when they were first constructed. New research led by the University of Utah has found that seawater filtering through the concrete leads to the growth of interlocking minerals that lend the concrete added cohesion.

Romans made concrete by mixing volcanic ash with lime (the product of baked limestone) and seawater to make a mortar, and then incorporating into that mortar chunks of volcanic rock, the ‘aggregate’ in the concrete.

Around 79 CE, Roman naturalist and natural philosopher Pliny the Elder wrote in his 37-volume encyclopedia Naturalis Historia about the natural capacity of volcanic ash to react with water: ‘as soon as it comes into contact with the waves of the sea and is submerged becomes a single stone mass (fierem unum lapidem), impregnable to the waves and every day stronger.’

The combination of ash, water, and quicklime produces what is called a pozzolanic reaction, named after the city of Pozzuoli in the Bay of Naples. The Romans may have gotten the idea for this mixture from naturally cemented volcanic ash deposits called tuff that are common in the area.
image_5011-Roman-Concrete.jpg


http://www.sci-news.com/archaeology/roman-marine-concrete-05011.html?utm_source=feedburner&utm_medium=email&utm_campaign=Feed:+BreakingScienceNews+(Breaking+Science+News)
 
 

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Pozzolanic reaction of volcanic ash with hydrated lime is thought to dominate the cementing fabric and durability of 2000-year-old Roman harbor concrete. Pliny the Elder, however, in first century CE emphasized rock-like cementitious processes involving volcanic ash (pulvis) “that as soon as it comes into contact with the waves of the sea and is submerged becomes a single stone mass (fierem unum lapidem), impregnable to the waves and every day stronger” (Naturalis Historia 35.166). Pozzolanic crystallization of Al-tobermorite, a rare, hydrothermal, calcium-silicate-hydrate mineral with cation exchange capabilities, has been previously recognized in relict lime clasts of the concrete.

http://ammin.geoscienceworld.org/content/102/7/1435
 
 

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Regarding Roman concrete - apparently it could help reduce global warming:

If the cold reaction of Roman marine concrete could be recreated, the cement manufacturing industry’s contribution to global warming would be dramatically reduced. This is the goal that Jackson, alongside others, including the US Department of Energy, are working toward. Although they have produced experiments in similar conditions, using water from the San Francisco Bay and volcanic materials from the west of the United States, the concrete they obtained does not possess the essential Roman characteristics. While the once secret ingredients have now been disclosed thanks to modern technology, Jackson acknowledges that they still have yet to determine the “preparation of the raw materials and the processing.”
https://elpais.com/elpais/2017/07/05/inenglish/1499249854_569819.html
 
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