"Ancient Roman concrete has proven to be far more durable than most modern-day concrete. Unlike modern mixtures that degrade over time, Roman concrete is known for its ability to actually strengthen when exposed to seawater, a quality found in structures like the Pantheon and coastal piers that have stood for nearly two millennia. The secret lies in a unique blend of volcanic ash (often collected from Mount Vesuvius), lime, and seawater. These minerals react chemically over time to form new crystalline structures, fortifying the strength and durability of the concrete itself. This “self-healing” property allowed Roman marine structures to endure and even thrive despite millennia of weathering, leaving modern scientists studying its composition as they seek to replicate its strength for future construction."