Tag Archives: Human Cause

Why Roman concrete still stands strong while modern version decays?

 

Scientists have cracked the secret to Roman water-based structures’ strength – and findings could help today’s builders

Scientist Marie Jackson has said Swansea lagoon’s seawall should be built using Roman concrete. Photograph: Tidal Lagoon Power/PA

Their structures are still standing more than 1,500 years after the last centurion snuffed it: now the Romans’ secret of durable marine concrete has finally been cracked.

The Roman recipe – a mix of volcanic ash, lime (calcium oxide), seawater and lumps of volcanic rock – held together piers, breakwaters and harbours. Moreover, in contrast to modern materials, the ancient water-based structures became stronger over time.

Scientists say this is the result of seawater reacting with the volcanic material in the cement and creating new minerals that reinforced the concrete.

“They spent a tremendous amount of work [on developing] this – they were very, very intelligent people,” said Marie Jackson, a geologist at the University of Utah and co-author of a study into Roman structures.

As the authors note, the Romans were aware of the virtues of their concrete, with Pliny the Elder waxing lyrical in his Natural History that it is “impregnable to the waves and every day stronger”.

Now, they say, they’ve worked out why. Writing in the journal American Mineralogist, Jackson and colleagues describe how they analysed concrete cores from Roman piers, breakwaters and harbours.

Previous work had revealed lime particles within the cores that surprisingly contained the mineral aluminous tobermorite – a rare substance that is hard to make.

The mineral, said Jackson, formed early in the history of the concrete, as the lime, seawater and volcanic ash of the mortar reacted together in a way that generated heat.

But now Jackson and the team have made another discovery. “I went back to the concrete and found abundant tobermorite growing through the fabric of the concrete, often in association with phillipsite [another mineral],” she said.

She said this revealed another process that was also at play. Over time, seawater that seeped through the concrete dissolved the volcanic crystals and glasses, with aluminous tobermorite and phillipsite crystallising in their place.

These minerals, say the authors, helped to reinforce the concrete, preventing cracks from growing, with structures becoming stronger over time as the minerals grew.

By contrast, modern concrete, based on Portland cement, is not supposed to change after it hardens – meaning any reactions with the material cause damage.

Jackson said: “I think [the research] opens up a completely new perspective for how concrete can be made – that what we consider corrosion processes can actually produce extremely beneficial mineral cement and lead to continued resilience, in fact, enhanced perhaps resilience over time.”

The findings offer clues for a concrete recipe that does not rely on the high temperatures and carbon dioxide production of modern cement, but also providing a blueprint for a durable construction material for use in marine environments. Jackson has previously argued Roman concrete should be used to build the seawall for the Swansea lagoon.

“There’s many applications but further work is needed to create those mixes. We’ve started but there is a lot of fine-tuning that needs to happen,” said Jackson. “The challenge is to develop methods that use common volcanic products – and that is actually what we are doing right now.”

Source:

https://www.theguardian.com/science/2017/jul/04/why-roman-concrete-still-stands-strong-while-modern-version-decays

Ex-climate change skeptic: Humans cause global warming

People Seem to forget how important this is, that is why I want to remind them, this is a article from 07/29/2012.

When the best scientists, including some of the few skeptics among them, study the data–and study it carefully and thoroughly–they too recognize the truth. And that was certainly true in the case of Cal-Berkeley physics Professor Richard Muller when asked to chair the Berkeley Earth Surface Temperature (BEST) project, set up for global warming skeptics. Now he too is among the unqualified believers. The evidence is strong and persuasive. And neither wishing it were not true, nor political spin, nor self-interested business denials, can change the truth of it at all. It’s what the data and analysis tell us. nbcnews.com reports:

Global warming not only is real, but “humans are almost entirely the cause,” a self-described former climate change skeptic has declared. “Call me a converted skeptic,” Richard A. Muller, University of California, Berkeley physics professor said in an opinion piece posted online Saturday in The New York Times.
Muller in October released results from the Berkeley Earth Surface Temperature (BEST) project, set up for global warming skeptics, that showed that since the mid-1950s, global average temperatures over land have risen by 0.9 degrees Celsius (1.6 degrees Fahrenheit).
In his new statement, Muller said, “Last year, following an intensive research effort involving a dozen scientists, I concluded that global warming was real and that the prior estimates of the rate of warming were correct. I’m now going a step further: Humans are almost entirely the cause.”

—“Ex-climate change skeptic: Humans cause global warming,” NBC News(7.29.2012)

For a useful review of the scientific opinion on global warming and the role of humans in it–including all the major scientific bodies that have affirmed it–see this article on Wikipedia, and others cited by it: “Scientific opinion on climate change.”