We’ve all heard the saying, “Rome wasn’t built in a day.”, but as it turns out, Rome was built to last. As evidenced by the famous Pantheon (completed in 125 C.E)—which boasts the world’s largest unreinforced concrete dome—the Romans were onto something over 2,000 years ago. Thanks to a recent discovery by scientists who analyzed ancient Roman concrete samples from the walls of Privernum, what has been an enduring mystery to archaeologists has now been revealed. The Romans’ biggest engineering secret? A combination of lime and hot mixing.
Scientists used to believe that Roman concrete was able to heal when cracked because it was made of volcanic ash and water. Recently, researchers at MIT and Harvard used Advanced Light Source and scanning electron microscopy with energy disbursement spectroscopy to dig deeper. The researchers noticed that relic limestone chunks were the largest in Privernum’s concrete matrix, and didn’t buy the often-misattributed explanation of “just poor mixing.” They discovered that these chunks were calcium deposits (called “lime clasts”), and could have only formed at extremely high temperatures. It became clear that this combination of material and process—quicklime and hot mixing—is responsible for Roman concrete's self-healing and regenerative capabilities.
If you’d like to learn more about the granular science behind this, check out this paper on Mechanistic insights into the durability of ancient Roman concrete published in the journal of Science Advances.
We’ve known all along that if you want to build something cheap you can use an unproven solution. For instance, one popular cost-cutting method of soil stabilization in present day are cheap alternative liquid stabilizers. If you want to build something that lasts, you’ve got to use a solution that has stood the test of time. That’s where Lime comes in. Let’s do as the Romans did.