In the 2nd century BC, Roman engineers created a groundbreaking innovation in construction technology called opus caementicium. This was not just a building material; it was a long term investment in the infrastructure of the empire and a way to protect valuable property. Unlike modern concrete that degrades, this ancient mixture was designed for incredible longevity, securing the future success of Rome. The secret was a special mix of volcanic ash and lime which, when exposed to seawater, spark