Why didn't ancient Roman concrete erode in sea water?

[Angela]

See:

[FONT=&quot]http://www.archaeology.org/news/5710-170705-roman-ocean-concrete

"Modern concrete, when placed in the presence of sea water, erodes over time. According to a report in BBC News, scientists led by Marie Jackson of the University of Utah examined samples of ancient Roman concrete from ancient harbor structures with an electron microscope, X-ray micro-diffraction, and Raman spectroscopy in an effort to learn why it gained strength from exposure to sea water. The tests, conducted at the Lawrence Berkeley National Laboratory, revealed crystals of a rare mineral known as aluminum tobermorite growing throughout the samples of concrete, in addition to a porous mineral called phillipsite. The mineral crystals continued to grow in the Roman mix of volcanic ash and lime, which reinforced the concrete over long-term exposure to sea water. A similar chemical reaction has been detected in underwater volcanoes. “Their technique was based on building very massive structures that are really quite environmentally sustainable and very long-lasting,” Jackson said."[/FONT]

 

[Yetos]

that is old,

In Greece they use θηραικη γη (Santorine volcanoe dust)
and other pozzolans

Ποζολανες pozzolans it is knowed from antique for their aluminosillicate materials,
pozzolans name is after Vezuvios (vesuvio) are



Minoans first used dust of Thera volcanoe with lime stone and lime stone dust (Παιπαλη-filler)

the Vezuvios pozzolans contain also an extra material called θιξοτροπικη γελη a dust that with water turns to gell and is fantastic to cover the concrete outside the surfaces that might come in touvh with water.

the θηραικη γη has simmilar more water proof results, that is why was prefered at Suez channell

the what is called Roman concrete problem is that takes long time to turn to solid, and acts as a gell longer period, than modern Portland type

Anecdotal is that eggs (shell and yolk) help pozzolans to gain more strength, a belief that reach even our times,

deposits of θηραικη γη

Φλεγραια πεδια campi flegrei and Vesuvio volcanoe was major mines of Roman concrete

old style concrete from pozzolans could take weeks to gain serious strangth and become solid monolithic construction.
and can gain strength for years via the circle of wet-dry

Romans understood the plastic abillities of concrete and used it quite massive, especially in architectural designs that might need longer period than build with other materials,
enormous quantities were mined from Vezuvios volcanoe

 

[LeBrok]

I heard that eggs were used in cement mortar in medieval Poland too, but I thought the egg whites were used.

 

[LABERIA]

I heard that eggs were used in cement mortar in medieval Poland too, but I thought the egg whites were used.

Yes even here in South Albania, Ali Pasha of Tepelena built many bridges, aqueducts, castles and other fortifications and the white of egg and the wool was used in cement mortar.

 

[Yetos]

As far as I know Yolk not white,


in Fact all the bridges build in Epirus Makedonia Roumeli and Liapides (S Albania) are maid by yolk and no white part of egg,
their concrete has yolk and lime stone gell with clay

<<Ο κρόκος του αυγού επίσης, είναι γνωστό ότι έχει συγκολλητικές ιδιότητες, >>
egg yolk has abillities of connect

a mix called curasan κουρασανι

source
http://gefyria.blogspot.gr/2008/11/blog-post_8978.html


that water reserve tank has history of 2900 years Kamiros Rhodos island
made by pozolans of Aegean

that is the crystal that is made using Θηραικη γη (Thera's ashes, Santorin earth)
stratlingite

that is the known Roman structure of Pantheon

And that is the crystal that is created by Pozzuoli sand concrete (pozzolana)
tobermalites

in fact we know East Roman empire concrete that was used in churches at 900 and simmilar to Agia Sophia today (by 2001 Moropoulou)

 

[bicicleur 2]

indeed, volcano dust
I've read somewhere that the Romans got their first concrete in Pozzuoli
the concrete came out of small underwater craters and even solidified under water

 

[wicket]

With regard to sea water, pozzolon concretes have a tighter pore structure and resist the infiltration of chlorine ions, which are destructive.