The Pantheon of Rome, built about two thousand years ago, still continues to amaze for its extraordinary resistance. His unailed concrete dome, still intact after centuries, is one of the largest ever made. The ancient infrastructures of the Empire, such as the aqueducts and ports, made with the same material, have exceeded unscathed centuries of use and weather. But how did the Romans create such a resistant cement? And above all, is it possible to reproduce that material today sustainable?
The question is not only historical or architectural: it is climatic. Modern concrete is the backbone of global infrastructure, but its production is one of the main sources of CO₂ emissions to the world, responsible alone by about 8% of global emissions. In a context in which the decarbonisation is increasingly urgent, some researchers wondered if the Roman cement was not only more durable, but also more ecological.
The answer, however, is not so simple.
A more complex environmental balance than it seems
Both modern and Roman concrete are based on a common ingredient: limestone. However, the processing process of the Romans was much less energetive. While modern cement, known as Portland, is produced by heating limestone and clay at temperatures of about 1,450 ° C, the Romans obtained their mortar by heating the limestone at only 900 ° C. The limestone thus treated was then mixed with water and pozzolana, an abundant volcanic powder in the Pozzuoli area, near Naples, from which it takes its name.
This combination triggered a chemical reaction that gave life to an extremely stable and durable binder, capable of resisting centuries of mechanical and environmental stresses. An advantage that the modern concrete still manages to guarantee.
But how much is this ancient technique really “green”? To find out, the team of researchers led by Martinez led a detailed analysis, modeling the consumption of energy, water and the emissions necessary to produce different types of Roman concrete, using both ancient and modern methods.
Both modern and Roman concrete are based on a common element: limestone. However, the production processes differ deeply. The current cement, known as the Portland cement, is obtained by heating limestone and clay at very high temperatures, up to 1,450 ° C, a process that consumes a lot of energy and produces about 8% of the global CO₂ emissions.
The Romans, on the other hand, used a lime -based mortar: they warmed the limestone at a much lower temperature, around 900 ° C, and mixed it with water and pozzolana, a fine volcanic ash from areas such as Pozzuoli, near Naples. This ingredient gave rise to a particularly stable chemical reaction, responsible for the resistance over the time of the material.
A recent study led by Daniela Martinez, engineer of the Universidad of Norte in Colombia, has compared the environmental impact of the production of Roman cement with the modern one, using current technologies. The results? Disappointing for those who hoped in a low emission alternative. Roman concrete, also produced with modern technologies, generates similar quantities of CO₂ or even higher per cubic meter compared to the modern one.
However, there is a positive side. The Roman method produces less atmospheric pollutants such as nitrogen and sulfur oxides, substances linked to respiratory diseases. Based on the energy source used, these emissions can be reduced between 11% and 98%.
The true force of Roman concrete is in its incredible longevity
If the production process of Roman concrete is no longer “green”, its durability could be the real winning card. While many modern concrete structures require important maintenance or replacements after a few decades, the Roman buildings survived for centuries, if not millennia.
However, there is an important structural difference: the Romans did not use steel armor, a fundamental element today but subject to corrosion, one of the main causes of the degradation of modern concrete. As Paulo Monteiro, engineer of the University of California in Berkeley points out, compare the two technologies requires caution, because modern infrastructures are subjected to pressure and stresses very different from those of the ancient world.
According to the study, so that Roman concrete can be truly more sustainable, should guarantee a duration between 29% and 97% higher than the modern one in applications such as roads and bridges. Considering the longevity demonstrated by ancient structures, this goal seems plausible, even if it is not guaranteed at all.
In some specific situations, with certain production processes, Roman cement could be more advantageous in environmental terms. According to Martinez, the value of Roman concrete is not so much in the recipe itself, but in the constructive philosophy that accompanies it: a culture of permanence, of the construction designed to last centuries, not only decades.
Today, the most effective solution for sustainable construction may not be to blindly imitate the Romans, but rather to combine their attention to durability with current technological innovations. Investing in long -lasting materials, reducing the need for maintenance and replacements, and optimizing energy sources are the real steps forward for a more sustainable building future.
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