Not unsuccessful. It looks mathematical. Every six months the world rediscovers Roman concrete and marvels at the durability of a material that has allowed Agrippa’s Pantheon to stand for 2,000 years (whereas modern concrete cracks after a few decades). Meanwhile, with almost the same regularity, there is a scientist or engineer who claims to have found the key secret that makes it so. Now it’s the Massachusetts Institute of Technology’s turn, and as usual, history is not quite what it seems.

What does the study say? MIT researchers studied tiny bits of lime commonly found in Roman concrete: ‘calcium oxide crumbs’. This type of structure has been extensively studied in Roman infrastructures in the maritime context and has been associated for years with a certain ‘self-renewal’ capacity of the material.

According to some scientists, water that would enter through cracks in the concrete would carry calcium ions from the clasts in a process that would result in the formation of calcite and sealing the cracks. MIT’s recent work also examines these cullet in terrestrial concrete, and theorizes that they were a result of the Romans adding quicklime to the concrete mix (instead of slaked lime — calcium hydroxide — the key to pozzolanic reactions).

Beyond that, the researchers made various blends with quicklime and confirmed their theory that limescale (and crack-repairing calcite) formed in these new mixes. As Brian Potter said, the discovery is historically interesting. But despite attempts to sell it to us as revolutionary, it is potentially useless.

Useless? Yes, it doesn’t work. Many mistakes are made when talking about Roman concrete, but there are two recurring mistakes: First, the “survivor bias,” as Manuel F. Herrador, professor of Structural Concrete at the University of A Coruña School of Roads, always reminds us. The idea of ​​the exceptional quality of Roman concrete comes from fully examining the best structures they have made, the best preserved. Instead, much of what the Romans built is now completely gone and cannot be studied.

The second mistake is that we are comparing “cherries with menas” on a functional level. Frankly, we cannot do with Roman concrete one-tenth of what we do with modern concrete. The most obvious example is reinforced concrete (i.e. a mixture of concrete with reinforcing steel). These materials allow us to solve many of the structural problems that concrete presents (in fact, they allow us to build buildings like existing structures with long and relatively narrow “pieces”, something impossible with Roman construction techniques), but for these advantages, we have to pay a cost. The most obvious: structures rust earlier.

We make the concrete we want to make. This is perhaps the most important thing to keep in mind when talking about Roman concrete: We don’t do it because we don’t want to make “Roman concrete”; because it’s not worth it for what we want to achieve. Potter himself gives examples (“Hindu and Buddhist temples built to last over 1,000 years”) that show that current science and technology allows for real fancy stuff. The question is, do we want to make them in a world that is changing so fast, and no, we don’t like the Romans as much as we love them. Good thing: it allows us to go much further.

Image | Dimitry B.