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Researchers have unlocked the chemistry of Roman concrete which has resisted the elements for thousands of years.
Ancient sea walls built by the Romans used a concrete made from lime and volcanic ash to bind with rocks.
Now scientists have discovered that elements within the volcanic material reacted with sea water to strengthen the construction.
[...] 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.
Source: BBC News
American Mineralogist DOI: 10.2138/am-2017-5993CCBY
(Score: 4, Interesting) by Immerman on Wednesday July 05 2017, @04:18PM (3 children)
That is a second factor definitely - as rebar rusts it expands and shatters the concrete. But modern concrete suffers from spalling and other degradation problems as well. It's a pretty safe to bet that nothing made in the last few centuries will still be around and structurally sound after two thousand years, even if it didn't incorporate rebar or other metal reinforcements.
There's a somewhat related "joke" in the southwest - government officials finally decided to allow traditional adobe construction to satisfy construction code requirements, provided it was reinforced with rebar. The natives acquiesced, while commenting amongst themselves that in a few hundred years archaeologists were going to wonder how and why they had these strange red circles perfectly lined up between all the tiers of adobe brick in their walls.
(Score: 3, Informative) by bob_super on Wednesday July 05 2017, @06:40PM (2 children)
You must not live in an Earthquake area.
I went to the epicenter of the 99 quake in Taiwan. I ain't living in a stone house without rebar, unless it's massively overbuilt stone like the Romans did for their major works.
Similar images to what I saw there:
http://blogs.agu.org/landslideblog/files/2010/10/09_03-collapsed-bridge-rebar.jpg [agu.org]
http://umich.edu/~acemrl/NewFiles/library/bridge_column.jpg [umich.edu]
http://db.world-housing.net/static/data/100108/101107_111_09.jpg [world-housing.net]
http://db.world-housing.net/static/data/100108/101115_111_17.jpg [world-housing.net]
http://db.world-housing.net/static/data/100108/101112_111_14.jpg [world-housing.net]
http://db.world-housing.net/static/data/100108/101118_111_20.jpg [world-housing.net]
http://db.world-housing.net/static/data/100108/101119_111_21.jpg [world-housing.net]
(Score: 2) by Immerman on Wednesday July 05 2017, @10:15PM (1 child)
I'm not denying the usefulness of rebar, especially under high-stress conditions where you can be fairly certain that it will crack at some point and lives will be on the line.
Rebar buys you time when a structure starts to fail for unrelated reasons. But it also pretty much guarantees that your concrete will shatter over time, regardless of outside stresses. So long as you don't care if your structure lasts more than a few decades, rebar is a valuable addition. If you want it to last longer than that, then you need to look elsewhere for reinforcement (and yes, massively "overbuilding" is one viable option)
(Score: 2) by kaszz on Thursday July 06 2017, @12:38AM
The solution is likely some material that won't serve as a conduit for moisture. Maybe some Teflon impregnated carbon fiber will do it?