Irish buildings used contaminated building blocks.

[Alistair_Heaton]

Seems to be a colossal problem with mica in building blocks.

https://www.rte.ie/brainstorm/2021/0929/1249617-mica-concrete/

 

[1503-44]

Couldn't access the link, but this list tells the problem,

https://duckduckgo.com/?q=mica+in+building+blocks&t=brave&ia=web

https://www.irishmirror.ie/news/irish-news/young-irish-mum-tells-how-13077958

 

[FacEngrPE]

Some more technical information in this piece.

“These issues were never envisaged by block manufacturers nor indeed reflected in the industry standards set down by the Government.
“We welcome and embrace the recent introduction of regulations for increased block strength in line with expert recommendations. We further welcome that local architects are now specifying the use of blocks which are 2.6 times stronger than the previous Government standard and that experts are recommending the use of a render type which is appropriate for Donegal weather conditions.

Apparently the building regulations allowed this block.
This particular problem can and has occurred when incorrect aggregate is included in a concrete mix.

 

[MacGyverS2000]

The main effect of the presence of mica in concrete mixtures is to increase the water demand due to the hydrophilic nature of the mineral. This reduces what is known as the workability of the fresh concrete mix, which is how easy the mixture can be transported, placed, compacted and finished; and this, in turn, reduces the compressive strength of the finished concrete.

I know the amount of water used during mixing is crucial to a proper cure... does this mean increased water during mixing will alleviate this particular issue?

Dan - Owner

http://www.Hi-TecDesigns.com

 

[Alistair_Heaton]

Just so you know it absolutely blows a gale in Donegall and slashes it down with rain pretty much every 3-4days as the depressions crossing the Atlantic make landfall. Its a gorgeous place but make sure you have a good rain coat.

 

[1503-44]

I think it also has something (perhaps even more) to do with grain interlock being adversely affected. Mica is made up of near perfectly flat layers so there is no interlock between the mica and other sand particles or carbonate crystals of the cement. What's more is that the flat layers of the mica itself easily tear apart. There is no bond internally or externally within or to the mica. The same problem occurs when near perfectly spherical beach or Sahara or Empty Quarter desert sand is used in the mix. The spheres do not bond well with the cement. There are remarkably few locations left on earth where good sand for making cement can be acquired.

 

[SwinnyGG]

I know the amount of water used during mixing is crucial to a proper cure... does this mean increased water during mixing will alleviate this particular issue?

The wording of that passage in the article is confusing/misleading. It reads to me like it was written by someone who doesn't know anything about concrete.

Mica in concrete does increase water demand (that part is correct) and reduce workability for a given water/cement ratio, but the water attached to the mica is still active in hydrating the cement (ie it isn't just captured and removed from the chemically active component of the mix). Reduced workability in itself does not reduce concrete strength; but adding water does.

What's critical in concrete mix design is the ratio between water and cement. As this ratio goes up (more water is added per given quantity of cement) concrete strength goes down. You want your concrete as 'dry' as possible for high strength; this is why water reducing admixtures exist.

So the presence of mica reduces the strength of the concrete through mechanical effects, AND it also increases the water required to yield a certain level of workability in the final mix, which in turn reduces the strength of the concrete matrix through chemical effects as well.

 

[waross]

If all aggregate in Ireland was rich in mica, I would expect that poor concrete strength would have long ago become part of the local collective knowledge of concrete durability.
Has a block maker openned up a borrow pit that is much higher in mica content than historically used aggregates?

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[LittleInch]

Irish mirror story has a table at the end which shows it was nearly all one particular supplier between 200 and 2008 and affects about 400-500 homes.

So not really a large catastrophe, but certainly is if you onw one of those houses...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[RedSnake]

I would expect that poor concrete strength would have long ago become part of the local collective knowledge of concrete durability.

A assumption on my part is that this is a part of Ireland getting a lot of money from EU building up there infrastructure and businesses and even new homes.

With a new building bom I expect that metods and "new" material has been used by contractors that isn't from Ireland and that what is normally working in other places do not work here because the materials have another composition then they are used to.

But it is just as you have thought me, a wild ass guess. ;-)


“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[1503-44]

"$ $ $ $" from Google and Facebook.

500 houses at say € 200,000 each is 100MM.
We've certainly talked a lot longer about things costing a lot less.

 

[Alistair_Heaton]

From what I can tell these blocks were made by local businesses. And marketed to meet the local demand.

And as red says the place was booming around that time and building materials in short supply.


What I presume has happened is that a farmer had sand on there land and either them or someone else realised that demand way outstripping supply for concrete blocks in the area and the price of them was at a premium. So they started making them. local transport rates and cheaper and don't have to wait they were easily sold.

The roads at that time were pretty horrible in the area both to southern Ireland and shall we say there was complications getting across the border to NI.

Now to me sand is sand until this thread I had no clue that you couldn't just use any sand to make cement and concrete up just knew you should use builders sand and get it from a supplier don't collect it from the beach.

I suspect my fellow Celts were in the same boat. Big sand pit not a beach that will do....

All the businesses that sold them will be bankrupt now or shut down. The builders that bought them in good faith and I presume certified. Quiet what the process is to certify a concrete block is I have no clue.

Irish Builders do have a reputation in the UK but I have tried to stay away from that as the ones in the UK tend to have links with the traveling community. And I am sure the local ones working their local area are completely different as they live locally and are interested in continued business not get the cash and run.

 

[FacEngrPE]

I recently obtained some mix designs from a local concrete supplier, It is fascinating to see what concrete wizards mix together to get different properties. The one job I looked at has 10 different mix designs used with wildly different properties,

 

[SwinnyGG]

Yeah that's pretty common. The project I'm working on right now has about 8,200 LF of curb & gutter, and we have 4 different mix designs just for that. Modern concrete gives us a lot of different tools to do what we need. Part of the reason I like heavy concrete work so much.