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Stalactites at Cape Point toilets

RUG
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Stalactites at Cape Point toilets

Unread post by RUG » Sun Sep 04, 2016 12:32 pm

Hi there!
I saw these "stalactites" hanging from a concrete overhang at the toilets at Cape Point. I thought it was quite a strange place to find them, especially considering the fact that the concrete from which they are hanging can't be too old. So I'm wondering what these are composed of. I thought maybe salt from the sea water. Does anyone have an idea?
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Elsa
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Re: Stalactites at Cape Point toilets

Unread post by Elsa » Mon Sep 05, 2016 12:31 pm

RUG, I have seen that before in other cement structures and my guess is its the calcium in the cement leaching out and forming those stalactites, but also open to other suggestions! :?
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Philip1
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Re: Stalactites at Cape Point toilets

Unread post by Philip1 » Tue Nov 08, 2016 12:51 pm

Hi Rug and Elsa :D

Sorry, i only came across this topic now. :|
Hope the following will shed a bit more light. :)


Concrete stalactites
220px-Mostar_interchange_concrete_stalactites.jpg


Concrete stalactites.
Stalactites can also form on concrete, and on plumbing where there is a slow leak and limestone (or other minerals) in the water supply, although they form much more rapidly there than in the natural cave environment (description and experiments see literature).
The way stalactites form on concrete is due to different chemistry than those that form naturally in limestone caves and is the result of the presence of calcium oxidein concrete. This calcium oxide reacts with any rainwater that penetrates the concrete and forms a solution of calcium hydroxide. The chemical formula for this is:
CaO(s) + H2O(l) → Ca(OH)(aq)2
Over time this calcium hydroxide solution reaches the edge of the concrete and, if the concrete is suspended in the air, for example, in a ceiling or a beam, then this will drip down from the edge. When this happens the solution comes into contact with air and another chemical reaction takes place. The solution reacts with carbon dioxide in the air and precipitatescalcium carbonate.
Ca(OH)(aq)2 + CO(g)2 → CaCO(s)3 + H2O(l)
When this solution drops down it leaves behind particles of calcium carbonate and over time these form into a stalactite. They are normally a few centimeters long and with a diameter of approximately 5 mm (0.20 inches).
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Elsa
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Re: Stalactites at Cape Point toilets

Unread post by Elsa » Wed Nov 09, 2016 9:00 am

Thanks for the extra info Philip! :thumbs_up:
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hilda
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Re: Stalactites at Cape Point toilets

Unread post by hilda » Wed Nov 09, 2016 4:50 pm

Very interesting! Thanks for the information Philip1! :clap: :clap:
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