Lime Clasts and Heat: The Romans' Secret Sauce

In the second century A.D., Roman emperor Hadrian commissioned a temple dedicated to the gods. To this day, the Pantheon still possesses the largest unreinforced concrete dome in the world. How do these ancient Roman concrete structures withstand the test of time? Well, superior engineering for one. For example, skilled artisans used lighter aggregates higher in the Pantheon's dome. Roman seawalls owe their extreme longevity in part to their “self-healing” capacity. Exposure to seawater facilitated the continued growth of crystalline structures in the concrete. Researchers have also focused on volcanic ash as a secret to the durability of Roman concrete...