June 18, 2013

A Concrete Example of the Modern Benefits of Ancient Technology

I will never forget the disbelief I felt when my undergraduate art history professor mentioned that civilization had lost the recipe for concrete. This seemed preposterous. I've walked on a sidewalk before, skipped down the paved path as a child, watching diligently to not step on cracks for fear of “breaking my mother’s back”, as the old saying warned. We have concrete!

What she went on to explain was that the original recipe for the highly durable Roman concrete had been lost to history. For thousands of years, people have tried to reverse engineer this seemingly simple technology. It has been quite a challenge. Though we have concrete now, it is not the same as the concrete used by the Romans. The concrete we use in modernity is actually pretty poor in comparison to the Roman concrete of the past. Think about it for a moment. Roman concrete roads, aqueducts, and structure are still doing well considering there antiquity. Consider all the times you've driven down a road of potholes or walked down a sidewalk with pits and cracks and questioned, “Didn't they just pave this a few years ago?” 

While some of this may be seen as planned obsolesce, it is still testament to the relative inefficiency of modern concrete, most of which lasts only decades. Commonly, what is used is Portland cement. We have been using this recipe for over 200 years, not a bad recipe, but compared with the durability of Roman concrete, it falls flat, especially when exposed to salt water. 

After years of research, scientists in the US and Europe have finally figured out the recipe to Roman concrete. The findings are published in this month's issues of the Journal of the American Ceramic Society and American Mineralogist, a publication to which I’m sure you all subscribe. ;)

According to the scientists, "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." It is because of this lime and volcanic ash mixture that Roman concrete has such tremendous binding ability. 

It gets better, though. Not only is this concrete far superior in durability, but unlike modern concrete, it is more environmentally sustainable. The manufacturing of most modern concrete accounts for 7% of greenhouse gas emissions. With these new, ancient methods, we have the potential to make amazingly durable structures and live in harmony with the environment. 

I wonder what other lost technology we may find and for use in modernity? It is my belief that ancient civilizations possessed a number of technologies that we may never fully understand. Since they used the natural resources around them, a lot of evidence of such “green” technologies may have simply decayed or been lost to history, though some have not. 

Between the pyramids, Baghdad Battery, and the Antikythera mechanism, just to name a few, there is little doubt that the ancients were far more advanced than they are commonly depicted. 

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