Efflorescence facade (concrete)

[Vinterkatten]

Be careful with hydrochloric acid, if it splashes into your eyes when you dilute it, you can go blind. The hydrochloric acid corrodes everything with lime, so yes. It removes paint that is lime-based. But I think it looks like salt deposits. I actually don't think acid removes salt at all. I usually use a hammer or a sharp paint scraper when I remove salt deposits. These particular deposits are probably quite rare, feels like some kind of construction/material defect. But my experiences are that deposits don't disappear over time.

I may be wrong, but I've never seen such lime deposits.

Thanks for the response. If it becomes necessary to try to remove it with hydrochloric acid, we will hire a company for this.

Maybe it is salt deposits and not lime deposits, I was just guessing lime. Is it safe to taste it lightly?

It should be possible to scrape off on the decorative brick, I'll test it gently. I think it will be more difficult on the painted plaster.

 

[Vinterkatten]

Regardless of what the efflorescence is, moisture must be involved for it to precipitate.

Most likely, lime efflorescence, it looks like the plaster has cracked, allowing moisture to enter the cracks and cause lime efflorescence.
You should bring in an expert to look at it on-site.
Don't waste time trying to remove the efflorescence, instead ensure that the cause is eliminated so that they disappear as well, otherwise they will continue.

If it has dripped onto other things, you can use Gel Hammer, but be careful and read the instructions carefully so you don’t apply it to surfaces that can be etched.

Salt is less likely.

Thank you for your response. Yes, it seems I'll have to bring in a company to look at it and possibly address the issues. I was mostly curious about what it was and if, once it's addressed, the problems would return again after a year or so.

 

[Vinterkatten]

If you look at the 3 "drops" under the tile, it looks like salt.
Haven’t seen lime stay like that.
You can feel them, if they are hard it is salt.
If they are porous, it is lime.

If it’s lime, it can be washed off with weak hydrochloric acid on the brick wall anyway.
Or use a dry root brush/scrub brush.
[link]
Probably works on salt too.

I went to feel the drops today and they are not soft. They were a bit porous, could crumble a bit with my fingers, but the rest was hard.

 

[Vinterkatten]

Yes, definitely shrinkage cracks, probably because the moisture curing was missed and maybe there's a lack of mesh, or the mesh used was of the wrong dimensioning when it was plastered. However, for the sake of others, we don't need to go into such details when the question was about removing efflorescence.
Otherwise, we might start reciting Hooke's Law and calculating which mesh should be present in the plaster to resist shrinkage cracks.
These cracks continue upwards on the facade as far as we can see in the picture that was taken.
All it takes is driving rain on the facade for water to be transported through the cracks; even the dew point might be enough.

The brick facade is more problematic. Considering the amount of efflorescence, water is getting behind it; this can absolutely happen on a brick facade. However, the moisture is finding its way out at the wrong place. One usually lays waterproofing to direct the water to drainage holes at the bottom. It doesn't seem to work here since it appears above a window.
The drops look like lime; salt is much more porous than lime.
Regardless, the brick facade is poorly executed. If it's from 2019, he has until 2029 to address construction faults with the contractor. However, the burden of proof is on him, so he should bring in an expert to write a report to support his claim of construction faults.

You suggest it could be chlorides; where do you think they could be coming from?
It was a very long time ago that salt was used as an accelerator.
And if it were salt, it would dissolve with clean water.

I would recommend not using hydrochloric acid. Gel Hammer is a much better option as it's user-friendly and won't damage other parts of the house if it drips or splashes.
You apply it, and after 45 minutes, wash it off. The brick may need to be moistened beforehand so it doesn't absorb all the liquid too quickly.

Thank you for your response. I am sure the contractor hasn't done things correctly. However, they have gone bankrupt (and of course started a new company again), and we have an insurance case, etc. At this point, we're mostly interested in getting rid of the efflorescence to make it look a bit nicer. In the worst-case scenario, the facades might need to be completely redone, which will cost a lot of money for the housing association with 25 such houses all having these problems.

Thanks for the tip about Gel Hammer, will check it out!

 

[neo11]

Okay, it sounded serious that the builder went bankrupt.
25 houses, yes I don't know the size.
But it's going to be many millions.

 

[PatrikBL]

Thanks for the response. If it's necessary to try to remove it with hydrochloric acid, we will hire a company for this.

It might be salt deposits and not lime deposits, I just guessed it was lime. Is it safe to taste a little of it?

It should be possible to scrape it off the decorative brick, I'll test it lightly. I think it will be more difficult on the painted plaster.

Ask them not to use hydrochloric acid, you will have problems with corrosion if it splashes on other parts like metal sheets and windows, hydrochloric acid was abandoned 20 years ago.

It is lime, mortar does not contain salt but it does contain lime, you should not listen to neo11.

Thank you for your response. I am sure that the contractor did not do it right. However, they have gone bankrupt (and of course started a new company again) and we have an insurance case, etc. At present, we are mostly interested in removing the deposits to make it look a bit nicer. In the worst case, the facades may need to be completely redone and that would cost a lot of money for the housing association with 25 such houses all having these problems.

Thanks for the tip about Gel Hammer, I will check it out!

Sad about the insurance case, I hope it gets resolved eventually for you.

Out of pure curiosity, which company was the main contractor?

 

[xxargs]

In many contexts, it's not just lime in the deposits but also gypsum, and gypsum can be very insoluble and isn't dissolved by acid—and some of it comes from the sulfuric acid that comes with the rain, dissolves a bit of the mortar, and recrystallizes later when it dries up.

You can try with a small test with something like citric acid on an inconspicuous spot or preferably chip off a small piece and see how well it dissolves in a small cup with some citric acid dissolved in water—if it bubbles a lot, the piece falls apart and eventually disappears, it is mostly lime—if the piece doesn't disappear or break down, just bubbles a little in the acid solution and remains no matter how long you wait and is hard to crush the pieces, then it is largely gypsum (calcium sulfate) and in some crystal forms can be very insoluble and dissolved by practically nothing.

It might be possible to find facade cleaners with complexing agents (EDTA or similar) that work (slowly) on gypsum, but otherwise, it's difficult.

 

[PatrikBL]

In many contexts, it's not just lime in the precipitates but also gypsum, and gypsum can be very insoluble and isn't dissolved by acid. Some of it comes from sulfuric acid that comes with the rain, dissolves a bit of the mortar, and recrystallizes later when it dries up.

You can try a little test with, for example, citric acid in an invisible spot or rather chip away a small piece and see how well it dissolves in a small cup with a bit of citric acid dissolved in water. If it bubbles a lot, the piece crumbles and eventually disappears, it's mostly lime. If the piece doesn't disappear, only bubbles a little in the acid solution, remains no matter how long you wait, and is hard to crush, it's mostly gypsum (calcium sulfate) and in some crystalline forms can be very insoluble and dissolves in practically nothing.

You might find facade cleaner with complexing agents (EDTA or similar) that works (slowly) on gypsum, but otherwise, it's tough.

Isn't it gypsum plaster used here?

Gypsum can be dissolved with water; if it has been damp for a long time, the gypsum turns into clay.
I've encountered situations where cove has been put on footings with gypsum plaster and then sealed on top. You could scrape off the gypsum with your fingers after a month.

 

[xxargs]

The gypsum comes from the fact that rainwater contains a trace of sulfuric acid from emissions from the combustion of oil and coal, what is referred to as the acidification of lakes, etc., also affects mortar, lime mortar, cement, concrete, etc., and dissolves lime over time and depletes it. Perhaps not as problematic today as in the 70s and 80s when non-desulfurized fuel oil was burned and the Germans sent their coal smoke almost unfiltered (Ruhr area...) and much of it ended up over Sweden - that's what builds up the gypsum part of lime mortar and cement/concrete over time and can cause such deposits when it finds its way out through, for example, various cracks.

Gypsum exists in several crystalline forms with water, some of which are particularly insoluble.

In these contexts, it is almost always a mixture of gypsum and calcium carbonate (the latter is dissolved due to the carbonic acid that dissolves in rainwater and gives a more soluble calcium bicarbonate from the lime mortar and when the carbonic acid evaporates again, such as by drying, the insoluble calcium carbonate precipitates again and builds up the deposits.

 

[neo11]

Strange that PatrikBL hasn't responded yet.
But at least he knows that there is no salt in bruk.
But that's good, now I know that too.

 

[PatrikBL]

The gypsum comes from the fact that rainwater contains a bit of sulfuric acid due to emissions from the combustion of oil and coal, which is referred to as acidification of lakes, etc., and also affects mortar, lime mortar, cement, concrete, etc. It dissolves lime over time and depletes it. This might not be as problematic today as it was in the 70s-80s when they burned non-desulfurized fuel oil and the Germans sent their coal smoke almost untreated (Ruhr area...) and much of it ended up over Sweden – this builds up the gypsum part of the lime mortar and cement/concrete over time and can cause such deposits when it finds a way out, such as different cracks.

Gypsum exists in several crystalline forms with water, some of which are particularly insoluble.

In contexts like this, it’s almost always a mixture of gypsum and calcium carbonate (the latter is dissolved due to carbon dioxide that dissolves in rainwater and gives a more soluble calcium bicarbonate from the lime mortar, and when the carbon dioxide evaporates again, for example through drying, the insoluble calcium carbonate precipitates again and builds up the deposits.

That is correct, but I don't think TS wants to go into molecular level here but wants to know how to remove the lime deposits.

Salt efflorescence that neo mentioned is something else and occurs when moisture travels through the concrete, then it appears more like roses on the wall, and we don't see that here. And of course, it's not common salt but different types of lime.
Both are effectively dissolved by Gel Hammer.

In this case, it's an aesthetic question since the BRF has an ongoing case.

 

[Vinterkatten]

Ask them not to use hydrochloric acid, you will have problems with corrosion if it splashes on other parts like plates and windows, hydrochloric acid stopped being used 20 years ago.

It's lime, mortar does not contain salt but rather lime, you should not listen to neo11.

Unfortunate with the insurance case, I hope it works out for you eventually.

Out of curiosity, which company was the main contractor?

City Entreprenad i Malmö AB, stay away from them and the companies they are involved with.

 

[neo11]

That is correct, but I don't think TS wants to go into molecular levels here, rather wants to know how to remove the lime deposits.


Salt deposits as neo mentioned are something different and occur when moisture travels through concrete. It then looks more like roses on the wall and that's not what we see here. And of course, it's not about ordinary salt but different types of lime.
Both are effectively dissolved by Gel Hammer.

In this case, it is an aesthetic issue as the BRF has an ongoing case.

All this talk about Gel Hammer, do you get a commission?

 

[PatrikBL]

So much talk about gel hammer, are you getting a commission?

Nope, not a penny, it's just good.
Keep working with your acid and trowel before the boss sees you standing around fooling with your phone.

 

[neo11]

Ok, continuing with that.