What did the Romans ever do for us? They didn’t, however, teach us how to produce their remarkable concrete, which continues to astound material experts as it withstands the test of time.
Structures over 2,000 years old do not exhibit the same problems as modern structures do. The material’s secret has long eluded us, but experts believe they have finally discovered it. They reproduced concrete in the lab with strikingly identical qualities, which could lead to the development of better and more sustainable concrete today.
Pozzolan, a reactive volcanic powder from the city of Pozzuoli, just outside Naples and near the notorious Mount Vesuvius, is an important element in Roman concrete. A popular method for making concrete is to mix calcite with water to get hydrated quicklime, which is then mixed with pozzolan and more water.
A different method, known as hot mixing, involves mixing quicklime immediately with pozzolan and water without first hydrating it. This results in some suspended chunks known as lime clasts. These constructions have been discovered in concrete throughout the Roman Empire.
Members of the Massachusetts Institute of Technology’s Masic Lab were intrigued by their appearance. They can undoubtedly emerge in various ways when the concrete is not correctly mixed, but their pervasiveness suggests that they were intended features rather than accidents.
And this is a fantastic find. Concrete cracks and water permeate those cracks over time. Cracks in this form of concrete preferentially travel through lime clasts and begin to recrystallize in the presence of water. The concrete prepared in the lab using the hot mixing process was able to self-heal, and water was no longer running within the crack after two weeks.
Concrete production accounts for around 7% of total global carbon emissions. There is a lot of study being done on ways to reduce this, including employing new manufacturing methods. This hot-mix concrete would do this simply by being more durable.
“Imagine having a construction material that is extremely durable, lasts a long time, and reduces the amount of maintenance required on a structure.” It decreased the cost of rebuilding a structure,” lead scientist Dr Linda Seymour told IFLScience. “First and foremost, that reduced the use of material.”
The Masic Lab is also working on several types of sustainable concrete, ranging from concrete that can store power to concrete that can actually absorb carbon dioxide.
