Roman concrete was used to construct the magnificent pantheon, which has endured for two millennia.

Researchers discover secret recipe of Roman concrete that allowed it to endure for over 2,000 years

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Ancient Rome’s concrete recipe is an impressive feat in architectural history. Some Roman buildings are so spectacular in their construction and beauty that modern builders would never attempt something similar, even with today’s technology. Now engineers are beginning to understand why ancient Roman concrete was so revolutionary.

Rome built many of its buildings and monuments with concrete made of lime, volcanic sand, and volcanic rock. The ancient Romans’ buildings and structures, some of the most spectacular in the world, have withstood chemical and physical onslaught for 2,000 years and are still standing.

An advanced concrete recipe allowed the Romans to constructed magnificent structures that no builder would dare to attempt today

An advanced concrete recipe allowed the Romans to constructed magnificent structures that no builder would dare to attempt today. Source: BigStockPhoto

Previous research has already found that Roman concrete was far superior to our own modern concrete, which is made to endure about 120 years.

It’s been known for a while that the volcanic sand used in Roman concrete and mortar made their buildings last for so long.  Now a new study by a group of engineers and engineering researchers has discovered the precise recipe that made the Roman concrete endure much longer than concrete used today.

The researchers used an ancient recipe written down by Roman architect Vitruvius to mix a batch of mortar. The engineers let it harden for six months and looked at it with microscopes. They found that clusters of a dense mineral form through the Roman process. These strätlingite crystals, formed by the volcanic sand as it binds with limestone, prevented the spread of cracks by reinforcing interfacial zones. Interfacial zones are weak links inside the concrete.

A magnified piece of Roman concrete consisting of lime, volcanic sand, and rock

A magnified piece of Roman concrete consisting of lime, volcanic sand, and rock ( Wikimedia Commons )

It isn’t just that Roman concrete is more lasting. It is also not as bad for the environment in the manufacturing of it because the mix only needed to be heated to 900 Celsius as opposed to the 1,450 of modern concrete.

“Stronger, longer-lasting modern concrete, made with less fuel and less release of carbon into the atmosphere, may be the legacy of a deeper understanding of how the Romans made their incomparable concrete,” Ancient-Origins.net wrote in 2013 . Heating the limestone in 19 billion tons of Portland cement made annually accounts for 7 percent of human-released carbon into the atmosphere, according to the new study .

Ceiling in the Pantheon, made entirely from Roman concrete

Ceiling in the Pantheon, made entirely from Roman concrete. Credit: Giulio Menna / flickr

Rome is situated between two volcanic regions, Monti Sabatini to the north and the Alban Hills to the south. When Augustus became the first emperor of Rome in 27 AD, he initiated a building campaign. After builders settled on using Pozzolonic ash from the Alban Hills’ Pozzolane Rosse ash flow, Augustus decreed that Pozzolonic  mortar be the standard in Roman buildings. That decision cemented Rome’s enduring architectural legacy. Roman architects found that this mortar substantially improved the margin of safety in buildings, which were becoming more daring in their design.

The prototypical example of this may be the awe-inspiring Roman Pantheon, a huge concrete building capped by 142-foot dome. It was built in the second century AD.

The Roman Panethon, a huge concrete building that has endured for nearly 2,000 years

The Roman Panethon, a huge concrete building that has endured for nearly 2,000 years. Source: BigStockPhoto

“Made entirely out of concrete, without the reinforcing support of structural steel, no modern engineer would dare attempt such a feat, says David Moore , author of The Roman Pantheon: The Triumph of Concrete . ‘Modern codes of engineering practice would not permit such mischief,’” Smithsonian.com says .

Featured image: Roman concrete was used to construct the magnificent pantheon, which has endured for two millennia. Source: BigStockPhoto.

By Mark Miller

Comments

An elderly cousin was an engineer for the Golden Gate bridge. He told me that the concrete used in the structure was designed was formulated to last for centurie. Final hardening would take decades. I'm puzzled by the comment that modern concrete would last only 120 years.. Maybe the foundation of a taco stand is not destined for long life, but bridges and dams should endure for millenia with the proper maintence.

These buildings lasted this long, and the concrete is still just as hard as ever, through centuries and centuries, WITHOUT the proper maintenance. Civil engineering fell off pretty drastically after the fall of Rome. If our own structures were built with this knowledge, we could be assured that the abutments of our bridges could withstand the test of time, with MINIMAL maintenance.

That, aside from the fact that the process is less energy-intensive and therefore more efficient and achievable by folks at low levels of technology, to build lasting things. A total win. I want to use this admixture in my own foundations and buildings on my farm.

Indeed :) a great article with excellent information. There is also a find of ancient chinese mortar, using rice, either in the great wall of china or some other wall I cannot recall the documentary name or story. But I do remember reading about it late 2015. That chinese rice was mixed in, and it still has not diminished in bond strength.

We have lots of different grades of concrete, depending on the application desired. One of the great hazards to concrete is that it is porous and freeze/thaw cycles damage it as well as thermal expansion and contraction. Modern concrete is better than ever. The Pantheon has never had hundreds of thousands of vehicles cross it each day.
The facade of St. Paul's in Macau was made of concrete whose lime came from sea shells. It has withstood hurricanes, earthquakes, fire and the bombs of WWII.
Everyone can find something to point to, to pretend that we are now unworthy compared to those of ancient times. It just isn't so.

And none of our concrete does what you say either. All the modern situations you are talking about are steel rebar reinforced concrete, not JUST concrete There is a metal lattice that enables it to flex and withstand vehicle movement, so its inaccurate to say our modern concrete formula does it, our modern construction methods do it. If we were to use steel rebar inside the roman concrete there is no reason to think it would perform as well or better based on its performance with out that reinforcement. Bottom line, comparing a building to a road/bridge isn't a comparison. Additionally, the aqueduct system and all these building from rome for the most part still stands where it hast been pillaged for rocks, in spite of innumerable earthquakes. How long would our concrete last (again without rebar) in the same conditions?

Many bridges today need to be replaced, they crumble, from prolonged traffic vibration and weather. ancient roman concrete has been subjected to earthquakes and time and their well, primitive, enduring recipes. some ancient concrete dont last because its mixture was simply not handled properly. and some of what we see today is fallen apart because it was taken apart for other projects, by other rulers, and war.
The pantheon and parthenon both could not be replicated today with our concrete methods. I would say those may be the only two roman buildings that out do our tech.

Your analogies are strange? How about "Vermeer painted with oils that have held their brilliance for centuries, mind you, they wouldn't last 5 minutes on the keel of a North Sea trawler!"
Yeah right.
The item is telling of the wonder of Roman architecture and its building materials, it does not strive to call Lord Norman Foster a pratt, does it. Jeez.

Um... I realize this post is a couple of years old, but thought it prudent to mention: the article stated that modern concrete lasts about 120 years. Your "friend" claims that the cement used in the SF bridge would last a century. But you seem puzzled...?

A century = 1oo years, so if the article claims roughly 120 years, it would seem to be within the margin of error and corroborate your friend's claim.

So... again, why are you puzzled?

But bridges in the united states are lucky to last 50 years. Add in all the traffic and chemicals put on the roads and some last less. Maybe the golden gate,( but it has impeccable upkeep and great weather),. but most bridges in this country dont even have a 75 year lifespan.
Its a serious problem in our country (road infrastructure)along with the opioid epidemic

Also, salt water of any kind is modern concretes worst nightmare

Whether concrete, steel or stone, bridges will always need maintenance because of the action of the water, specifically in undermining them. Modern concrete also gets harder for decades and if properly mixed and cured, will endure for centuries. However, it's remarkable that concrete has been around so long.

Very interesting.

This resolution may be that the 'cement' they used in the concrete is material that has already been subjected to great heat and is actually pre-cooked. Hence the strength.

Only the ash was "pre-cooked". It's the limestone that needs to be cooked to make it work. In their cement and in modern cement.

cool

please look into the works of Hannibal Pianta, he attended the Milan Institute of technology in 1888 and conducted work in concrete from 1902(chicago) till his death in 1937(san antoonio). His works are still standing without much restoration work, to include Nel-stone blocks exposed to the elements.

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