The people of the Roman era gave many relics, both cultural and historical, to a number of buildings. One thing they don't tell you is how they can make such incredibly strong concrete.
The strength of Roman concrete has amazed scientists, as this material has been tested for its durability. Some buildings from the Ancient Roman Era still survive today.
The structure, which is more than 2,000 years old, appears to show no problems compared to modern structures. This secret material has eluded us for so long, so researchers investigated it.
As quoted from IFL Science, the researchers recreated concrete in the lab with very similar properties and it might even lead to the manufacture of better and more sustainable concrete today.
An essential ingredient for making Roman concrete was pozzolan, a reactive volcanic powder that originated in the city of Pozzuoli, just outside Naples and near the famous Mount Vesuvius. To make concrete, a common approach is to mix the calcite material with water to make hydrated quicklime, then mix it with pozzolan and more water.
An alternative method, called hot mixing, mixes the lime directly with the pozzolan and water, without pre-hydrating it. This leaves a few chunks suspended in it. These structures have been found in concrete throughout the Roman empire.
Members of the Masic Lab at the Massachusetts Institute of Technology find the existence of this material interesting. This material can definitely form by other methods when the concrete is not mixed properly.
"In every country that the Romans built, we will find these fragments. Maybe these clasts are not just the product of errors in the process. Maybe the technology led to the formation of consistent clasts," said senior author Professor Admir Masic.
"This clastic is incorporated into cement construction and can then serve as a source of calcium for the 'healing' process of cracked buildings," he said.
According to the researchers, this is an extraordinary discovery. Over time, the concrete cracks and water penetrates into the cracks. In certain types of concrete, the cracks move uniquely through the lime clast, and in the presence of water, the cracks start to recrystallize.
Concrete produced in the lab by the hot-mix method is self-healing and within two weeks water is no longer seeping into the cracks.
To note, concrete production contributes about 7% of global carbon emissions. There has been a lot of research on how to reduce it, including using different production methods. Hot mix concrete has the potential to do just that and make it even more durable.
"Imagine having construction materials that are extremely durable, which reduces the amount of maintenance you have to do to a building structure. It reduces how much you may have to rebuild a structure," said the study's lead author, Dr Linda Seymour.
Masic Lab also works on a variety of sustainable concretes in a variety of ways, from storing electricity to concrete that can actually absorb carbon dioxide.