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