What Makes Ancient Structures So Strong? 

From the Colosseum to the Pantheon, Rome is brimming with ancient wonders. In Spain, the ruins of a Roman jetty also remain standing, despite the fact that it was built more than 2000 years ago. Compared to modern architecture, these Roman relics are incredibly durable. So what makes them so robust?

According to experts, the engineering success of ancient Rome all depends on a ‘secret’ concrete recipe. The Romans didn’t hold back on building up an empire, which called for a huge amount of concrete. And despite the lack of modern technology they managed to perfect their blend.

The ‘secret’ recipe

To decipher the ingredients researchers at the University of California’s Lawrence Berkeley National Laboratory made micron-level X-ray studies of samples of used to construct piers, jetties and breakwaters during the Roman era.

The results were remarkable. While salt water is considered the downfall of modern structures, the Romans embraced it. By blending seawater with volcanic ash, lime and rock they pioneered a remarkable material that gains strength over time.

The power of minerals

When studying samples, the team found crystals of aluminous tobermorite, a multilayered calcium silicate hydrate mineral. It’s formed as seawater dissolves the volcanic ash, and plays an all-important tole in strengthening the concrete. The scans also revealed that the recipe triggered a second stage of phillipsite mineral growth, which also contributed to the strengthening process. Together, tobermorite and phillipsite mean that instead of crumbling as it ages, the concrete is able to form new minerals. These actively strengthen the concrete, and create structures that thrive in salt water.

“The Romans created a rock-like concrete that thrives in open chemical exchange with seawater,” explains geologist Marie Jackson from the University of Utah, who led the breakthrough study.

A new era of concrete

The findings were published in the journal American Mineralogist, and could mark an exciting new breakthrough for the concrete industry. Unlike the Roman recipe, modern concrete isn’t designed to change structure after it sets, which means that saltwater can cause cracks and breaks. IF a similar technique can be applied to modern concrete, the results could be remarkable.

While this study was conducted in California, the UK is also a global leader in research and innovation.  Now celebrating its 10th year, Diamond Light Source is the UK’s cutting edge synchrotron radiation facility. ‘Adding Electrons to Synchrotron Imaging Synergies’ offers an exclusive glimpse at the latest developments to come out of the facility, with a focus on how electron microscopy is helping researchers study samples at a large range of length scales.