Ancient Roman Concrete Could Self-heal Thanks to “Hot Mixing” With Quicklime
upstart writes:
Mysterious lime clasts, dismissed as defects, turn out to serve a useful purpose:
The famous Pantheon in Rome boasts the world's largest unreinforced concrete dome-an architectural marvel that has endured for millennia, thanks to the incredible durability of ancient Roman concrete. For decades, scientists have been trying to determine precisely what makes the material so durable. A new analysis of samples taken from the concrete walls of the Privernum archaeological site near Rome has yielded insights into those elusive manufacturing secrets. It seems the Romans employed "hot mixing" with quicklime, among other strategies, that gave the material self-healing functionality, according to a new paper published in the journal Science Advances.
[...] In his treatise De architectura (circa 30 CE), the Roman architect and engineer Vitruvius wrote about how to build concrete walls for funerary structures that could endure for a long time without falling into ruins. He recommended the walls be at least two feet thick, made of either "squared red stone or of brick or lava laid in courses." The brick or volcanic rock aggregate should be bound with mortar composed of hydrated lime and porous fragments of glass and crystals from volcanic eruptions (known as volcanic tephra).
[...] For this latest study, Masic wanted to take a closer look at strange white mineral chunks known as "lime clasts," which others had largely dismissed as resulting from subpar raw materials or poor mixing. "The idea that the presence of these lime clasts was simply attributed to low quality control always bothered me," said Masic. "If the Romans put so much effort into making an outstanding construction material, following all of the detailed recipes that had been optimized over the course of many centuries, why would they put so little effort into ensuring the production of a well-mixed final product? There has to be more to this story."
Read more of this story at SoylentNews.