Calcite formations on concrete

Hi all, new to the forums. I found this flowstone on some concrete steps the other day and it really surprised me as I had always been told that these formations take thousands of years to form. I often take groups down Pridhamsleigh Cavern and would hate to be giving them the wrong information (though it might be worth a white lie to keep people from taking them!).

I can't imagine the steps have been there more than 50 years and the cracks in them even less time. This seems like a very short time for these formations to appear? Is this a completely reasonable amount of time for a formation this size or is there something different going on here than in a karst environment?

Any help much appreciated! Thanks

Formations in these settings can form by the same process as those in natural caves (carbon dioxide loss and evaporation) or by the much faster mechanism that derives calcium carbonate from concrete. Concrete contains calcium silicates, and as it degrades, water leaches out calcium hydroxide, which is much more soluble than calcite.

So while regular cave formations grow as water loses carbon dioxide that it picked up far and wide, concrete formations can form rapidly as water absorbs carbon dioxide and redeposits it almost immediately. When the available calcium hydroxide is gone from the immediate vicinity of the drip, the rate of growth will slow, reverting to the traditional means if the setting allows, or even corroding and degrading if the setting dictates.

The growth rate of normal speleothems is slow, but impossible to predict or to extrapolate using current conditions. Different materials, water flows, and surface conditions change things. It is estimated that most large speleothems are tens to hundreds of thousands of years old. Growth rates as measured vary from .05 to 3.7mm per year.

In Redcliffe Caves (Bristol) straw stalactites, formed from water coming though the concrete in a brick arch, have grown 18 inches long in ten years.

There are very similar formations on the bricks on the side of my pond. 20 years max.

Thanks for your replies, extremely interesting, so it was the concrete! I have seen a few pools where the carbon dioxide from people in the cave has meant that formations have begun to be quickly eaten away, but never knew they could also grow so fast. I wonder if there is an application somewhere in repairing damaged formations or for use in museums...

jamboidhr said:

I wonder if there is an application somewhere in repairing damaged formations or for use in museums...

Click to expand...

Some years ago, on an extended tour of Postonja Jama during a conference, I remember discussing stal regrowth on formations that had been cut through to make the show cave path with Russ Gurney and Andrej Mihevc. Stal growth can most certainly occur at sufficient speed to be manipulated in the cause of conservation, although it can also be fast enough to embed damage, notably discolouration from algal growth and skin contact within previously white formations.

I was helping to build a new club house on a holiday park.  It involved breaking into a void below the pre-existing building which had a thick concrete cap on it.  I managed to get a photo of the dozen or so 5ft columns and hundreds of long straws which were exposed before the whole lot was destroyed the following day.  I tried to get them saved but it was to no avail.

I managed to get a photo of the dozen or so 5ft columns and hundreds of long straws

Click to expand...

Any chance of posting your picture here?

I've still got the photo but I took it about 25 years ago so it's not digital.  I'll see what I can do but it might take a bit of time.

I'm reminded of Midnight Creek Cave in California (US) that passes underneath a dam. The cave is a tallus cave formed purely from granite boulders, but just under the dam there are some calcite formations from the material leached out of the concrete above. Very neat to see while realizing you're standing underneath a dam.

Here some examples of formations in a fortress. The fortress wat build between  1888 and 1892. It was used in WWI and WWII. After WWII the fortress was abandoned and the concretions started to grow. So these concretions are roughly about 75 years old.






info about the fortress http://en.wikipedia.org/wiki/Fort_de_Saint-H%C3%A9ribert

BR

Dagobert L'Ecluse

Formidable ! 

JasonC said:

Formidable ! 

Click to expand...

An other very fine example of concretions with concrete as base is the abondoned boat tunnel of Godardville

A link to a photo page about this tunnel
http://www.scan-speleo.be/joomla/photos2?idx=1&albid=5271865963839379729&back=article&filter-search=db418991578fc72c8eb056c62119f50e

Dagobert