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Roman Concrete: 2,000 Years Of Strength

The secrets of the cement that joined a nation together


What's going on?

Throughout history, the Romans have constructed many buildings, some of which still stand today such as the Coliseum, the Pantheon, and the aqueducts. One of the enduring mysteries is how those structures are still standing despite minimal maintenance for most of their lives, compared to modern buildings which require frequent maintenance. The most significant example is the Roman piers. While current concrete piers require maintenance every 50 years or so, the ones built by Romans have lasted nearly 2,000 years with zero maintenance. Not only have they endured through the years, they instead became stronger over time.


A study conducted by researchers from the University of Utah found that the cement in their respective constructions makes the difference. Modern concrete is made of portland cement; a mixture of silica sand, limestone, clay, chalk and other ingredients which are melted together. However, when used to bind substances, the substances have to be chemically inert as otherwise, the chemical reactions that occur will weaken the concrete. Conversely, Roman concrete takes advantage of chemical reactions between its constituents to make it stronger. The main ingredient, in this case, is pozzolana: a type of volcanic ash.


Unfortunately for modern engineers, although we know the contents of Roman cement, the recipe has been lost to time. Not just that, the ash used in the ancient days is not commonly found around the world, and a substitute would be needed to reproduce the same result. However, if the puzzle could be solved, modern marine engineers could use a substance that is more environmentally friendly and can last for centuries with minimal reinforcement.


Why 2,000 Year-Old Roman Concrete Is So Much Better Than What We Produce Today