As was widely reported in July, a research team led by Paulo Monteiro (professor of civil and environmental engineering) of the US Department of Energy’s Lawrence Berkeley National Laboratory and the University of California, Berkeley, had been analyzing samples from a 2,000-year-old Roman concrete breakwater to determine why Roman seawater concrete is so durable, how its manufacture was more environmentally sound, and how to adapt those characteristics to modern concrete production.
“It’s not that modern concrete isn’t good. It’s so good we use 19 billion tons of it a year,” Monteiro said in a 2013 news release. “The problem is that manufacturing Portland cement accounts for seven percent of the carbon dioxide that industry puts into the air.”
Analysis of samples provided by team member Marie Jackson pinpointed why the best Roman concrete found in 2,000-year-old Roman piers, massive breakwaters, Trajans Markets (below) and the Pantheon in Rome, was superior to most modern concrete in durability.
Phys.org™ a leading web-based science, research and technology news service, updated this news in a July article. Ms Jackson and her colleagues found that seawater filtering through the concrete leads to the growth of interlocking minerals that lend the concrete added cohesion: when seawater percolated through the concrete in breakwaters and in piers, it dissolved components of the volcanic ash and allowed new minerals to grow from the highly alkaline leached fluids.
Marie Jackson says that the mineral intergrowths between the aggregate and the mortar prevent cracks from lengthening, while the surfaces of nonreactive aggregates in Portland cement only help cracks propagate farther. The results are published in American Mineralogist.
As ‘tufo’ volcanic rocks (tuff), common in and around Rome, are not found in many parts of the world, the team is experimenting with substitutions. A more immediate innovation, we suggest, would be further use of the ancient and durable French hemcrete (isochanvre) in Europe; more on this in the next post