MIT, Harvard, Italian, and Swiss scientists re-discover why Roman concrete structures last millennia while modern concrete doesn’t

Visiting the Pantheon, one of Rome’s premier tourist sites, it’s hard not be humbled by the knowledge that this building has lasted 1900 years and still stands as the world’s largest unreinforced concrete dome, while modern concrete structures deteriorate. Take a look at the magnificence of the Pantheon.

Photo credit: CC BY-SA 4.0 license

Photo credit: Macrons CC BY-SA 4.0 license

Photo credit: Anthony Majanlahti CC BY 2.0 license

The Romans’ concrete technology was lost for almost a millennium as the Dark Ages unfolded, and Europe regressed technologically and economically. The discovery of Roman manuscripts on making concrete in 1414 sparked gradual reintroduction of concrete as a building material, eventually including the use of reinforcing materials like iron bars that enabled feats that the Romans could not accomplish.

Yet for all our scientific and technical sophistication, Roman concrete resisted cracking and eventually crumbling far better than ours.

Now, as MIT News reports, scientists from MIT, Harvard, and 2 European research institutes have discovered the secret to Rome’s concrete recipe. We may finally be ending the Dark Ages for concrete. David L. Chandler writes:

The findings are published today in the journal Science Advances, in a paper by MIT professor of civil and environmental engineering Admir Masic, former doctoral student Linda Seymour ’14, PhD ’21, and four others.

The Romans used:

…volcanic ash from the area of Pozzuoli, on the Bay of Naples. This specific kind of ash was even shipped all across the vast Roman empire to be used in construction, and was described as a key ingredient for concrete in accounts by architects and historians at the time.

But moderns disregarded the presence in Roman concrete of:

…white chunks, often referred to as “lime clasts,” [which] originate from lime, another key component of the ancient concrete mix. “Ever since I first began working with ancient Roman concrete, I’ve always been fascinated by these features,” says Masic. “These are not found in modern concrete formulations, so why are they present in these ancient materials?”

If anything, the lime clasts were attributed to low quality, perhaps sloppy mixing practices, but they turned out to be the key to durability. Using quicklime a more reactive form of lime, the Romans reached high temperatures while mixing the concrete:

This is exactly correct. The quality of construction in this country is an international joke. Well at least for houses.

I’ve heard people from other countries say American homes are called “Canadian houses”, “paper houses” or “stick houses” depending on the country they’re from.

On the flip side why make something last if the neighborhood will invariably be a ghetto in a few decades after it’s built?

So they have discovered NOTHING. The use of pozzolan in concrete as a beneficial additive has been know for ages in the modern era.

Pozzolan / fly ash have been used in oilfield cements before began in the business nearly 50 years ago. It both decreases the permeability and somewhat lightens the mix. The benefit is dependent on the grind, the finer the better. Workability is also improved.

The only “discovery” in this is for Masic. Harvard tends to be a little slow on the uptake I guess.

99% of FReepers lack even a basic understanding of concrete. Doesn’t stop them from displaying their ignorance, however.

The Romans lacked both the knowledge about reinforcing steel and the ability to economically produce and transport it. Without it, the only path available to building the Pantheon was to use a super concrete.

Getting engineering info from a political blog is a serious mistake. And celebrating high temp mixes ignores all the risks that come along with it. I’m sure almost nobody commenting has ever heard of a flash set.

Typical FReepers getting their typing practice in.

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