Inspenet, September 20, 2023.
A team of scientists from the United States and Europe has carried out an exhaustive study on the concrete used by the Romans and believe they have discovered the secret: a type of concrete with the ability to repair itself .
For decades, researchers have tried to unravel the mystery behind this extremely strong ancient building material, especially in structures that faced harsh conditions, such as docks, culverts and seawalls, as well as in areas prone to seismic activity.
Lime: possible key component
Until now, the durability of Roman concrete had been attributed to its relationship with volcanic ash from the Bay of Naples region, Italy, which was distributed throughout the Empire for construction purposes.
However, scientists are focusing their attention on identifying another peculiarity: tiny, shiny white fragments that originate from lime, another component used in making concrete.
“Since I began working on the topic of Roman concrete, I have always been fascinated” by the presence of these pieces of material, MIT professor Admir Masic, co-author of the study published in the journal Science Avances, said in a statement. “They are not found in modern concrete, so why are they in ancient concrete?” he asked.
Until now, specialists assumed that these tiny fragments were the result of a poor combination of ingredients or low-quality raw materials. However, when using advanced imaging techniques to examine the concrete of a wall in the city of Privernum, Italy, they discovered that these small white fragments originated from calcium carbonate, which formed at extremely high temperatures.
This investigation led to the conclusion that lime was not only incorporated into the mixture with water, as was believed, but was used in the form of quicklime, generating a “hot mix” responsible for the remarkable solidity of the concrete. When cracks occurred, rainwater that came into contact with the concrete generated a saturated calcium solution, which then crystallized again in the form of calcium carbonate, thus allowing the cracks to be filled , according to the researchers’ conclusions. .
Self-healing concrete: from theory to practice
To test their theory, the researchers carried out experiments using the same process on cracked walls and the results showed that in just two weeks, the walls were completely repaired when they came into contact with water .
This important finding opens the possibility of commercializing a new modified concrete formula. As some modern buildings deteriorate within a few decades, scientists are hopeful that this discovery will contribute to reducing the environmental and climate impact associated with concrete production, which generates significant greenhouse gas emissions.