For the most part, we humans are better at things than we were thousands of years ago. But there are some things the ancients had down pat. Roman concrete, for instance, is just way better than anything we can whip up today. Finally, after some 2000 years, modern-day scientists have figured it out. And it's a secret worth knowing.
Concrete, while often not exactly pretty, is a super important tool of city-building today. We've been using Portland cement (an ingredient in concrete) as a binder for nearly 200 years as a building block of modern architecture, but it just can't hold a candle to that old Roman stuff. There are concrete harbours in Italy that are still doing pretty damn well after thousands of years. Meanwhile, a modern-day Portland cement structure is lucky to last 50 years when exposed to salt water.
Now, after years of research in labs across the US and Europe, scientists have figured out that the most robust Roman concrete is a specific mixture of lime and volcanic rock, the details of which have been published in this month's issues of the Journal of the American Ceramic Society and American Mineralogist.
The researchers described it this way in a press release on the subject:
The Romans made concrete by mixing lime and volcanic rock. For underwater structures, lime and volcanic ash were mixed to form mortar, and this mortar and volcanic tuff were packed into wooden forms. The seawater instantly triggered a hot chemical reaction. The lime was hydrated — incorporating water molecules into its structure — and reacted with the ash to cement the whole mixture together.
And it gets even better. Portland cement is environmentally messy to produce, accounting for some seven per cent of the C02 modern industry produces. Roman concrete? Much, much greener. There's still a lot of work to be done in adapting traditional Roman construction techniques to today's needs. But the recipe is as good as ever. We just have to get cookin'. [Bloomberg Businessweek]
Image: Carla Tavares/Creative Commons