Technology usually insinuates development, improvement and a succession of great ideas. However, when it comes to building concrete, our concrete today is only built to last a mere 100 years compared to ancient Romans concrete which have withstood the elements for more than 2,000 years.
A research team from the University of California, Berkeley comprising of engineers and geologists, are turning back the clock and learning lessons on how to make more sustainable and environmentally friendly concrete, by examining slabs of concrete that have been amazingly preserved for 2,000 years at the bottom of the Mediterranean Sea.
"The Romans developed a huge harbor infrastructure in the first century B.C. and first century A.D., and they built the harbors so well that they didn't need to keep repairing them," explained Marie Jackson, a researcher at the University of California, Berkeley's civil and environmental engineering department.
"It's a beautiful material, it's used all over the world, but the weakness is we use too much of it. We cannot continue with business as usual," says Paulo Monteiro, a researcher at the U.S. Department of Energy's Lawrence Berkeley National Laboratory. "We have to find alternative ways to make concrete."
The research team may have discovered an alternative to today's concrete after learning that manufacturing Roman concrete leaves a smaller carbon footprint than modern concrete.
Around 7 percent of global carbon dioxide emissions every year is caused by creating "Portland" cement, a key ingredient in modern concrete. In order to make it, fossil fuels need to burn calcium carbonate (limestone) and clays at about 1,450 degrees Celsius (2,642 degrees Fahrenheit).
However, "Sea" concrete used by Romans for harbor installations in the Mediterranean is made with a different concentration of materials than its modern counterpart. Instead of using fossil fuels, it was baked at a much lower temperature, resulting in a stronger concrete that is also less harmful to the environment.
The recipe for Roman concrete was described around 30 B.C. by Marcus Vitruvius Pollio, an engineer for Octavian, who became Emperor Augustus. "The not-so-secret ingredient is volcanic ash, which Romans combined with lime to form mortar. They packed this mortar and rock chunks into wooden molds immersed in seawater. Rather than battle the marine elements, Romans harnessed saltwater and made it an integral part of the concrete," the researchers noted in a statement.
The researchers' findings are published in two papers, one in the Journal of the American Ceramic Society, and the other scheduled to appear in the October issue of the journal American Mineralogist.
