Do as the Romans did
THE PROCESS of how concrete is made has progressed through the centuries, allowing the construction of sturdier structures. Today, however, new may not necessarily be better.
Recently, scientists from the University of California, Berkeley are looking into ancient Roman concrete that composes structures in Rome, Italy such as the Pantheon, Trajan’s Markets, and the Colosseum, which all have extraordinarily withstood the test of time.
In wharves of the centuries-old city, breakwaters and other harbor structures are made of the same ancient concrete. The research team, a report released by the university said, were particularly drawn more by the underwater concrete which “endured the unforgiving saltwater.”
In efforts to understand the longevity and endurance of Roman architectural concrete, an international and interdisciplinary collaboration of researchers used beams of X-rays at the Advanced Light Source of the US Department of Energy’s Lawrence Berkeley National Laboratory to examine the fine-scale structure of Roman concrete.
The article from UC Berkeley stated that the endeavor “described for the first time how the extraordinarily stable compound — calcium-aluminum-silicate-hydrate (C-A-S-H) — binds the material used to build some of the most enduring structures in Western civilization.”
The scientists believe that modern engineers can use the ancient technology to help improve the durability of modern concrete, “which within 50 years often shows signs of degradation, particularly in ocean environments.”
The manufacturing of Roman concrete is more environmentally friendly, too, as it leaves a lesser carbon footprint than its modern counterpart.
“The process for creating Portland cement, a key ingredient in modern concrete, requires fossil fuels to burn calcium carbonate or limestone and clays at about 1,450 degrees Celsius,” the report said. “Seven percent of global carbon dioxide emissions every year comes from this activity.”
On the other hand, producing lime for the ancient concrete needs temperatures that are “two-thirds of the required for making Portland cement.” Thus, the process is much cleaner.
Romans utilized lime and volcanic rock to form the concrete. Underwater structures, on the other hand, are made of slightly different materials. “For underwater structures, lime and volcanic ash were mixed to form mortar, and this mortar and volcanic tuff were packed into wooden forms.”
The findings also indicated that a hot chemical reaction occurs in the mixture when exposed to seawater. Water molecules are then incorporated into the structure as the lime is hydrated, cementing the mixture together.
However, the research team’s leader, Paulo Monteiro, a scientist at Berkeley Lab and a professor of civil and environmental engineering at UC Berkeley, said that the endeavor to improve modern concrete does not mean that it is inadequate. But he added that the Roman technique is greener than the modern method and more durable as it lasts for centuries.
“In the middle 20th century, concrete structures were designed to last 50 years, and a lot of them are on borrowed time,” Mr. Monteiro said in the report. “Now we design buildings to last 100 to 120 years. Yet, Roman harbor installations have survived 2,000 years of chemical attack and wave action underwater.”