The Romans’ self-healing concrete

One of the secrets to the success of Rome: self-healing concrete:

Photo by Life Of Pix on

Now, an international team has discovered ancient concrete-manufacturing techniques that incorporated several key “self-healing” properties. For years, researchers believed the key to the ancient concrete’s durability was one ingredient: pozzolanic material, such as volcanic ash from the area of Pozzuoli, on the Bay of Naples…

Historians say this specific kind of ash was shipped all across the Roman empire for use in construction projects, being described as a key ingredient for concrete at the time. After closer examination, these ancient samples also contain small, distinctive, millimeter-scale bright white mineral features. They were common component of Roman concretes. The white chunks — often called “lime clasts” — come from lime, another key ingredient in ancient concrete mix.

Masic adds that, during the hot mixing process, lime clasts develop a characteristically brittle nanoparticulate architecture. This creates an easily fractured and reactive calcium source, which could provide a “critical” self-healing ability for building materials. As soon as tiny cracks start to form within the concrete, they can preferentially travel through the high-surface-area lime clasts.

Prof. Masic explains that the material can then react with water, creating a calcium-saturated solution. It then recrystallizes as calcium carbonate and quickly fills the crack, or reacts with pozzolanic materials to further strengthen the material.

What I often wonder about inventions and techniques of the ancient world is how exactly they came about. How did Romans discover that a particular component – pozzolanic material – made concrete better in the long-term? I would guess there is evidence to suggest when this emerged and how it was dispersed but we may not know exactly how this formula developed.

If this could be incorporated into modern materials, could this make concrete even more important? I remember reading about the importance of concrete in How the World Really Works. Could this mean roads that do not need to be repaired as often, buildings that last longer, and numerous other applications?

This is also a reminder that infrastructure mattered for ancient empires and continues to matter today for modern everyday life. Even small improvements to basic materials or processes could have a tremendous effect given the scale and speed of today’s world.

Discovering underground Roman aqueducts

A group of amateurs have been tracing portions of Roman aqueducts hidden from view:

The group, which has been exploring underground Rome since 1996, has completed about 40% of its mission to map the aqueducts.”The famous arched, over-ground aqueducts we see today are just the tip of the iceberg; 95% of the network ran underground,” says Marco Placidi, head of the speleologists group, which is sharing its results with Italy’s culture ministry…

Dropping into the hole, Baldi disappears down the Anio Vetus aqueduct, a 3-foot-wide, 5-foot-high tunnel lined with pristine Roman brickwork. As frogs, spiders and grasshoppers scatter, Baldi reaches a maintenance shaft, complete with good-as-new footholds dug into the bricks that lead up to a narrow opening in the woods 10 feet above. Beyond him, the tunnel vanishes into the darkness…

“We have found Roman dams we didn’t know about, branch lines taking water to waterfalls built in private villas, and even aqueducts driven underneath” streams, Placidi said. “We are able to get up close and [feel we are] right back at the moment the slaves were digging.”

As the article notes, the level of construction here is quite amazing to survive roughly 2,000 years. But, without such underground aqueducts, the city of Rome may not have survived long.

What might happen to these infrastructure marvels? Perhaps they could be turned into tourist opportunities like the tunnels under Paris.

The highest-paid athlete of all time: a Roman charioteer

There is some discussion these days about the high salaries of modern athletes: are they worth it? Do these salaries demonstrate that society thinks these people are more or most valuable compared to others?

According to a new study, these high salaries are not just a feature of the modern era: a Roman charioteer is considered to be the highest paid athlete of all-time:

According to Peter Struck, associate professor of classical studies at the University of Pennsylvania, an illiterate charioteer named Gaius Appuleius Diocles earned “the staggering sum” of 35,863,120 sesterces (ancient Roman coins) in prize money…

Although other racers surpassed him in the total number of victories — a driver called Pompeius Musclosus collected 3,599 winnings — Diocles became the richest of all, as he run and won at big money events. For example, he is recorded to have made 1,450,000 sesterces in just 29 victories.

Struck calculated that Diocles’ s total earnings of 35,863,120 sesterces were enough to provide grain for the entire population of Rome for one year, or to fund the Roman Army at its height for more than two months.

“By today’s standards that last figure, assuming the apt comparison is what it takes to pay the wages of the American armed forces for the same period, would cash out to about $15 billion,” wrote Struck.

It sounds like Roman society was quite willing to make stars out of its athletes/competitors. I would be curious to know: what it is about societies that causes them to confer celebrity status and vast sums of money on people who compete (and win) in games or events?