Published: Thu, July 06, 2017
Economy | By Melissa Porter

Scientists Seek Secret Of Super Strong Roman Concrete

Scientists Seek Secret Of Super Strong Roman Concrete

While present-day oceanic concrete structures crumble in a matter of decades, 2,000 year old Roman breakwaters and piers are still intact to this day, and are stronger today than when they were first built.

"This alkali-silica reaction occurs throughout the world and it's one of the main causes of destruction of Portland cement concrete structures", University of Utah geologist Marie Jackson said in a news release. This combination of materials may result in the occurrence of "possolanic" reaction.

The conglomerate-like concrete was used in many architectural structures, including the Pantheon and Trajan's Markets in Rome. Massive marine structures protected harbours from the open sea and served as extensive anchorages for ships and warehouses.

Modern concrete is typically made with portland cement, a mixture of silica sand, limestone, clay, chalk and other ingredients melted together at blistering temperatures. Any reaction with the cement paste could result in the formation of gels that expand and break the concrete. As a matter of Fact, Dr. Jackson told the BBC earlier this year that the planned Swansea tidal lagoon should be built using the ancient Roman knowledge of concrete. One such factor, she says, is that the mineral intergrowths between the aggregate and the mortar which prevent cracks from lengthening, while the surfaces of nonreactive aggregates in Portland cement only help cracks propagate farther.

Writing in the journal American Mineralogist, Jackson and her colleagues explain how they analyzed the concrete core samples. The presence of Al-tobermorite surprised Jackson.

She said this revealed another process that was also at play.

The researchers coupled these analyses with a technique at ALS known as X-ray microdiffraction, and a technique at the University of California, Berkeley, known as Raman spectroscopy, to learn more about the structure of crystals in the samples.

Now a more detailed examination of the chemistry of the concrete showed significant amounts of that rare mineral growing out of another mineral naturally found in volcanic rock called phillipsite. Watching the last of the Romans, as scientists believe, and have created our own technology for the production of concrete. Methods to produce tobermorite-containing concretes at ambient temperatures could have a big impact, and Jackson's group is exploring this idea. "Oh - except the Romans!"

Scientists Seek Secret Of Super Strong Roman Concrete
Scientists Seek Secret Of Super Strong Roman Concrete

Ms Jackson said: 'As geologists, we know that rocks change. "Change is a constant for earth materials". Second, there is no way to tell that the exact mixture is that the Romans used; it might take years of experimenting before scientists can hit on the right formula.

What was ancient roman concrete made of? Platy crystals of Al-tobermorite have grown amongst the C-A-S-H cementing matrix. The interlocking plates boost the concrete's resistance to brittle fracture. They did it as the contrary to the new cement-based concrete contrary. Our modern cement, based on Portland concrete, is not supposed to change as it gets hard, so it goes without saying that any chemical reactions, especially with seawater will cause damage.

The mystery has nearly been solved by scientists, who have realized that ancient roman concrete is not only more durable, but it also becomes stronger in time.

Prof. Jackson is working with a geological engineer to rediscover the Romans' complex recipe for concrete.

'Romans were fortunate in the type of rock they had to work with. The mineral was formed by the heat produced as seawater, lime and volcanic ash reacted with each other. We've started but there is a lot of fine-tuning that needs to happen.

She is now working with Geological Engineer Tom Adams to prepare a replacement recipe, however, using materials from the Western U.S. The seawater used in her experiments was collected by Jackson herself from the Berkeley, California, marina.

In contrast to the modern concrete, which is made up of cement and crushed stone, its Roman ancestor is noticeably stronger.

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