March 4th, 2015
Worldwide, we use a lot of concrete—19 billion tons a year, to be exact. This material is used to create everything from apartment buildings to bridges to hydroelectric dams. It also generates a lot of greenhouse gases that contribute to global warming.
But a team of researchers at the University of California, Berkeley and Lawrence Berkeley National Laboratory found a better way to make concrete—thanks to an ancient Roman recipe.
The researchers compared modern concrete to Roman concrete ruins that have lain at the bottom of the Mediterranean Sea for 2,000 years. They discovered that the ancient concrete was made with volcanic ash and lime. When that mixture was submerged in seawater, a chemical reaction occurred that solidified the mixture into concrete. What’s significant is that the process required less lime than today’s processes, and only needed heating of just 900˚ C (1,652˚ F), which is much lower than current methods.
Today, the “glue” that makes concrete solid and strong is Portland Cement, made by mixing limestone and clay, and heating the mix to 1,450 degrees C (2,642 degrees F). Heating to that degree releases carbon-based greenhouse gases (about 7 percent of carbon dioxide that’s introduced each year comes from making Portland cement. The Roman way shows that you can make concrete that’s just as good (maybe better) with less heat, and therefore, less greenhouse gas.
Today’s concrete technology is designed to make buildings to last maybe 100, 200 years. It seems that 2,000 years later, the Romans weren’t just creating buildings that lasted longer, they were kinder to the planet.
Sources: University of California, Berkeley; Lawrence Berkeley National Laboratory
Jackson, m (2013). Unlocking the secrets of Al-tobermorite in Roman seawater concrete American Mineralogist
how romans built, ancient roman architecture, how to build with concrete