Wonder if any scientific entity has ever done an in-depth analysis of the concrete used to build the Pantheon in Rome...I hear it has held up for a pretty good stretch of time.
Oh yeah. BIG time. Still haven’t quite figured out the Roman’s secret yet. (Although volcanic ash and mild climate seem to be factors.)
Stories come up from time to time about someone rediscovering the Roman formula.
The Secrets of Ancient Roman Concrete
http://www.history.com/news/the-secrets-of-ancient-roman-concrete
There’s no doubt that the ancient Romans were master builders. Many temples, roads and aqueducts constructed during Roman times have held up remarkably well, despite the wear-and-tear—in the form of military invasions, tourist mobs and natural disasters such as earthquakes—they’ve had to endure. In particular, geologists and engineers have long been fascinated by Roman harbors, many of which stand almost intact after 2,000 years or more, despite constant pounding by seawater. Now, a team of researchers from Italy and the United States has analyzed a sample of concrete taken from a breakwater in Italy’s Pozzuoli Bay, at the northern tip of the Bay of Naples, which dates back to 37 B.C. Their findings, reported earlier this month in the Journal of the American Ceramic Society and American Mineralogist, may revolutionize modern architecture.
By analyzing the mineral components of the cement taken from the Pozzuoli Bay breakwater at the laboratory of U.C. Berkeley, as well as facilities in Saudi Arabia and Germany, the international team of researchers was able to discover the “secret” to Roman cement’s durability. They found that the Romans made concrete by mixing lime and volcanic rock to form a mortar. To build underwater structures, this mortar and volcanic tuff were packed into wooden forms. The seawater then triggered a chemical reaction, through which water molecules hydrated the lime and reacted with the ash to cement everything together. The resulting calcium-aluminum-silicate-hydrate (C-A-S-H) bond is exceptionally strong.
By comparison, Portland cement (the most common modern concrete blend) lacks the lime-volcanic ash combination, and doesn’t bind well compared with Roman concrete. Portland cement, in use for almost two centuries, tends to wear particularly quickly in seawater, with a service life of less than 50 years. In addition, the production of Portland cement produces a sizable amount of carbon dioxide, one of the most damaging of the so-called greenhouse gases. According to Paulo Monteiro, a professor of civil and environmental engineering at the University of California, Berkeley, and the lead researcher of the team analyzing the Roman concrete, manufacturing the 19 billion tons of Portland cement we use every year “accounts for 7 percent of the carbon dioxide that industry puts into the air.”
(more at link.)
They have and it is a synthetic zeolite type which was also used in other ancient structures. The sea wall at Herculeum is still whole near Pompei. We could use it now but it costs 7x normal concrete today. Back then they didn’t have the cheap stuff.