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Ancient Roman buildings have long been a popular draw for both tourists and academics. The endurance of amazing architectural accomplishments such as Rome's Pantheon has piqued experts' interest in how they continue to stand nearly two thousand years after the Roman empire's peak. While the lifespan of these constructions may be attributed entirely to Roman concrete, questions remain concerning the specialty and materials utilized in the concrete itself.
Ingredients for Roman concrete
According to a study published in the journal Science Advances, an international team of researchers led by the Massachusetts Institute of Technology (MIT) discovered that not only are the materials slightly different than previously thought, but so are the techniques used to mix them.
One important ingredient was pozzolan, or ash. The Romans utilized volcanic ash from the Italian city of Pozzuoli and transported it around the empire. At ambient temperatures, the silica and alumina in the ash undergo a pozzolanic reaction with lime and water, resulting in a stronger, longer-lasting concrete.
Another important element is lime clasts, which are microscopic fragments of quicklime.
These clasts give Roman concrete its self-healing properties. Concrete weathers and degrades with time, yet water may seep through its crevices and reach the clasts. When the clasts react with water, they form crystals called calcites, which fill the crevices.
Difference with modern-day cement
The high-temperature kiln technique used to produce contemporary Portland cement crushes all components into fine powder. It destroys the lime clasts, resulting in the loss of Roman cement's self-healing characteristics.
The Romans used a technique known as hot mixing, which included combining quicklime with pozzolan, water, and other components and heating them. The MIT researchers discovered that this procedure activates the lime clasts' self-healing abilities and can result in faster setting than cement manufactured using a quicklime-water solution known as slaked lime.
