Scientists uncover the secret to the strength of Roman concrete

The ancient representatives of Roman culture were masters of engineering and construction, as their aqueducts, buildings and ports in many cases survived for two centuries. A group of scientists have studied specific they used, and he thinks he’s found the key: quicklime.

Researchers have been trying for decades to unlock the secret of this super-strong ancient building material, especially in structures that endured particularly harsh conditions such as piers, culverts and dams, or those built in seismically active locations.

A new study published in the journal Science Advances and signed by researchers at the Massachusetts Institute of Technology (MIT), Harvard University and labs in Italy and Switzerland has uncovered ancient manufacturing strategies. specific which included several key features.

For many years it was believed that the key to the longevity of this specific It was based on an ingredient, pozzolanic material, volcanic ash from the Pozzuoli region in the Gulf of Naples (Italy), which was referenced in the stories of architects and historians of the time.

However, these ancient specimens also contain small, characteristic, millimeter-scale, shiny white minerals that have long been recognized as a ubiquitous component of mineral deposits. concretes the Romans.

lime chips

Often referred to as “chips of lime”, these white chunks come from lime, another key component of the ancient limestone mixture. specific.

Such leftovers have so far been considered mere evidence of careless mixing or low-quality raw materials, the Massachusetts Institute of Technology explained in a statement.

However, a new study suggests that these tiny pieces of limestone gave specific hitherto unknown self-healing ability.

One of the participants in the study, Admir Masic of the Massachusetts Institute of Technology, emphasized that if Romans They put so much effort into creating an exceptional building material, why did they put so little effort into ensuring they produce a well-blended end product?” so I thought there must be a reason.

After further characterizing the limestone clasts using high resolution multi-scale imaging and chemical mapping techniques, the researchers gained new insight into the potential functionality of these limestone clasts.

Historically, it was thought that when lime was added to Roman concrete, it first mixed with water to form a highly reactive pasty material in a process known as slaking, but this process alone could not explain the presence of lime chips.

So the team wondered if the Romans could have used quicklime, which is a more reactive form of the material. By studying samples of old concrete, they determined that the white particles were indeed composed of various forms of calcium carbonate.

“Key of super-strong nature”

Spectroscopic examination showed that they were formed at extreme temperatures, as would be expected from the exothermic reaction caused by the use of quicklime instead of or in addition to the slaked lime in the mixture.

Hot mixing, according to the team, was actually “the key to the ultra-strong nature” of the material. specific due to two factors, Masic explained.

On the one hand, when specific generally heated to high temperatures, this allows chemistry to be carried out that would not be possible if only slaked lime was used, producing compounds associated with these temperatures that would not otherwise be formed.

In addition, raising the temperature significantly reduces the curing and setting time, as all reactions are accelerated, allowing for much faster construction.

The team set out to prove that this mechanism is responsible for durability. specific Roman, producing samples of hot mixes incorporating ancient and modern recipes, cracking them open and running water through them.

After two weeks, these holes were completely healed and water could no longer flow, however, an identical piece specific made without quicklime, never cured and water continued to flow through the sample.

Masic believed that “it is interesting to think about how these formulas specific stronger formulas can extend not only the life of these materials, but how it can improve the durability of 3D printed concrete.”

(As reported by EFE)

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