Washington: An international team of geologists and engineers looking for a way to make concrete more durable and sustainable has found inspiration in the ancient Romans, whose massive concrete structures have withstood the elements for more than 2,000 years.
Using the Advanced Light Source at Lawrence Berkeley National Laboratory (Berkeley Lab), the researchers from the University of California, Berkeley, examined the fine-scale structure of Roman concrete.
It 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 discovery could 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 also leaves a smaller carbon footprint than does its modern counterpart. The process for creating Portland cement, a key ingredient in modern concrete, requires fossil fuels to burn calcium carbonate (limestone) and clays at about 1,450 degrees Celsius (2,642 degrees Fahrenheit).
Seven percent of global carbon dioxide emissions every year comes from this activity. The production of lime for Roman concrete, however, is much cleaner, requiring temperatures that are two-thirds of that required for making Portland cement.
The research team was led by Paulo Monteiro, a UC Berkeley professor of civil and environmental engineering and a faculty scientist at Berkeley Lab, and Jackson, a UC Berkeley research engineer in civil and environmental engineering. They characterized samples of Roman concrete taken from a breakwater in Pozzuoli Bay, near Naples, Italy.
The researchers also described a very rare hydrothermal mineral called aluminum tobermorite (Al-tobermorite) that formed in the concrete.
"Our study provided the first experimental determination of the mechanical properties of the mineral," said Jackson.
While Roman concrete is durable, Monteiro said it is unlikely to replace modern concrete because it is not ideal for construction where faster hardening is needed.
But the researchers are now finding ways to apply their discoveries about Roman concrete to the development of more earth-friendly and durable modern concrete.
The researchers` findings are published in two papers, one that appears online in the Journal of the American Ceramic Society, and the other scheduled to appear in the October issue of the journal American Mineralogist.
ANI
