Michelle Starr, in her Science Alert article, talks about lumps of lime in Roman concrete. For centuries this was dismissed as “sloppy mixing.” And as you might imagine, that isn’t quite the story, or I wouldn’t be writing this article.
MIT civil engineer Linda Seymour and her team determined that these lumps made the concrete “self-healing.” They have reverse-engineered the process for creating those lumps and have documented the mechanism. A mere couple of millennia after the original methods were forgotten, we are on our way to having commercially viable self-healing concrete.
Beyond just giving us the possibility of making structures with little incremental cost that will last millennia rather than decades, there are promising applications to 3-d printing.
Presumably, the latter of these was unanticipated by the ancient Romans.