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The BBC is running this story http://www.bbc.com/news/science-environment-40494248 [bbc.com] under the headline,

Scientists explain ancient Rome's long-lasting concrete

Since there have been many other attempts at explaining how the Romans managed to make better cement/concrete than we can today, it might be good to withhold judgement for now. But the story is compelling,

In previous tests with samples from ancient Roman sea walls and harbours, researchers learned that the concrete contained a rare mineral called aluminium tobermorite.

They believe that this strengthening substance crystallised in the lime as the Roman mixture generated heat when exposed to sea water.

Researchers have now carried out a more detailed examination of the harbour samples using an electron microscope to map the distribution of elements. They also used two other techniques, X-ray micro-diffraction and Raman spectroscopy, to gain a deeper understanding of the chemistry at play.

This new study says the scientists found significant amounts of tobermorite growing through the fabric of the concrete, with a related, porous mineral called phillipsite.

The researchers say that the long-term exposure to sea water helped these crystals to keep on growing over time, reinforcing the concrete and preventing cracks from developing.

"Contrary to the principles of modern cement-based concrete," said lead author Marie Jackson from the University of Utah, US, "the Romans created a rock-like concrete that thrives in open chemical exchange with seawater."

Soylentils discussed this topic a couple of years ago, https://soylentnews.org/article.pl?sid=15/07/12/1356242 [soylentnews.org] but a punctuation malfunction seems to have diverted the discussion...

Volcanic Rocks Resembling Roman Concrete Explain Record Uplift in Italian Caldera

The Beeb goes on to say,

The ancient mixture differs greatly from the current approach. Modern buildings are constructed with concrete based on Portland cement.

This involves heating and crushing a mixture of several ingredients including limestone, sandstone, ash, chalk, iron and clay. The fine material is then mixed with "aggregates", such as rocks or sand, to build concrete structures.

The process of making cement has a heavy environmental penalty, being responsible for around 5% of global emissions of CO2.

Original Submission