Concrete built and used by the ancient Romans has weathered the elements for thousands of years, proving to be one of the most durable man-made materials. Now, researchers have found out why, and are looking into how this could possibly be used today.
Old sea walls built by the Romans were constructed using a mixture of lime and volcanic ash to bind rocks together. Scientists say that the elements in the volcanic material used reacted with seawater over time to make the walls virtually indestructible, the BBC reports.
This discovery could lead to more environment-friendly building materials. Unlike modern-day concrete, which erodes over time, these walls have long baffled researchers. Instead of eroding, especially since they are in seawater, the walls seemed to become stronger.
Previous samples from the ancient sea walls and harbors showed that the concrete contained a rare mineral named aluminum tobermorite. This substance is believed to have crystallized in the lime as the concrete generate heat when exposed to seawater, making it stronger.
Researchers have conducted a more in-depth examination of the samples using an electron microscope, X-ray micro-diffraction and Raman spectroscopy. Along with tobermorite, they found a porous mineral called phillipsite. According to them, the long-term exposure to seawater helped the crystals grow over time, reinforcing the concrete and preventing cracks from happening.
Marie Jackson from the University of Utah, lead author on the study, said, “Contrary to the principles of modern cement-based concrete, the Romans created a rock-like concrete that thrives in open chemical exchange with seawater.”
It’s a very rare occurrence in the Earth.
Jackson is testing new materials using seawater and volcanic rock from the western USA, and has said that the planned Swansea tidal lagoon should be constructed using this ancient Roman technique. “Their technique was based on building very massive structures that are really quite environmentally sustainable and very long-lasting.”
However, there are limiting factors that make this approach challenging. First, there appear to be no suitable volcanic rocks. Second, there is no way to tell that the exact mixture is that the Romans used; it might take years of experimenting before scientists can hit on the right formula.
The study was published in American Mineralogist.