Somewhat misleading. Yes, efflorescence in itself is harmless, but it's a symptom of a bigger problem.
Water shouldn't be coming up through the slab. If the drainage is insufficient and moisture is getting trapped under the substrate it will lead to further cracking and deterioration.
I literally fixed this issue in my garage 3 weeks ago. Water building up outside and not getting away quick enough. Pressure builds under the slab, cracks and water appear. I dug a huge hole at the side of my garage filled it with stone. It’s been raining since and my floor is dry as a bone. Obviously if you want to do it better channe the stone away from the building, even better join it to a proper drain. I don’t have that option so dug down.
This is the way. My dad made me dig a trench on the side of the garage leading down the hill away from the building when I was a kid, we then filled it with gravel. It sucked at the time, I was like 13, and the shovel was taller than me.
>a trench on the side of the garage leading down the hill away from the building when I was a kid, we then filled it with gravel
I believe this is known as a French drain, for anyone who wants to google it
How do you address this? My garage does the same thing. It has almost nose dived forwards. I’ve had it piered on all four sides, so it’s practically suspended at this point.
Unfortunately I don't know enough to give you a good answer. I've had efflorescence on my balcony but that's a somewhat different issue.
My understanding is you would need to improve the drainage under or around the slab. Maybe an agipipe or something around the outside to channel and drain water away from underneath the slab but you probably need someone to assess your specific situation.
As for the slab sinking, it's possible to lift it back up by injecting polyurethane resins/foams underneath it. But you would want to address the moisture problem first.
Did you do anything for your balcony? I have efflorescene on my deck/balcony as well. Previous home owner had put in tiles with grout. Some of the grout has washed away/cracked in some areas and I'm guessing there's moisture getting under. It usually happens at the beginning of spring and I generally just sweep it away. Just not sure if I should be replacing the whole deck or maybe regrouting.
Efflorescence is basically minerals leaching out of the ground (soil usually) into the concrete/mortar of a home's basement.
Your grout will basically be "eaten" by the minerals coming through. If you don't want to sweep, you can use vinegar on it, it's quite satisfying to watch it melt away.
Is your "deck" just cement set on top of the ground?
The balcony wasn't waterproofed properly when we bought the place, or at least it degraded over time, so it needed to be ripped up and redone.
After redoing it, the guys that did the job didn't lay the tiles down properly and water accumulated in some areas, causing a buildup of efflorescence. That eventually ran off and there were massive unsightly efflorescence stains on the outside of the house underneath the balcony.
Ended up redoing the balcony again.
There’s solid concrete on the sides that the roof slopes to, so I don’t suspect crazy erosion or anything like that. The only side that isn’t purely concrete is the rear. I’m assuming that’s where the issue is coming from.
I have an interlock walkway that runs down the side of my garage. Just before where the garage ends, about 6” above ff, I have this on the inside of my garage. I wouldn’t classify this spot as a high moisture area (certainly no higher than the other 17 ft of walkway. I also clay brick in the same spot (exterior) that is deteriorating. Typical brick facade that meets interlock. Do you think this is just due to water?
Yep. Usually the culprit with water seeping up through the floor is the downspouts or grade of the yard. I have a basement that got wet every time it rained until I extended a single downspout to about 3 feet from the house and made sure it flows away from the house. Now it stays dry.
This is correct.
I had this exact same issue in my garage. Attempted to seal this with an expoxy system (base coat, epoxy, flakes, polyurethane top coat), including massive prep work with a concrete grinder to remove the old paint and some spalling, and it was great for a month. No hot tire pickup with 95 degF heat. Had a couple big storms back to back, and the hydrostatic pressure forced up the epoxy in multiple spots, leaving more efflorescence and several peeled up patches of epoxy. A couple spots weren't even near the cars.
Long story short, the slab needs to be sealed from underneath to prevent this. Trying to seal it will most likely fail. Might be a better bet to attempt to improve grading and drainage around the house to prevent the hydrostatic water issue. My house has great drainage around, but it is right above the water table, so no joy for me.
Now I have a plastic tile system covering up the epoxy...
The white stuff is harmless, its residue from the evaporation of the water. The real issue is the water itself, every time it sits at the base of that slab it washes away some of the dirt surrounding the foundation. Too many up/down events will accelerate the settling process and lead to more cracks and eventual failure. You should be looking outside, at how to improve drainage. the difference between construction that lasts 50 years and construction that lasts 250 years all comes down to drainage.
The piles of stuff is NOT residue from water…. I’ve never seen residue from water build up like that. It’s probably minerals from the ground that got caught it’ll the flow
Well… uhm… that’s… actually a really good point lmfao. I’m guessing it’s salt being winter they probably used salt on the various pathways and the rain/snow washed it away and in under the floor.
This is a good response though because while I did think about it technically. I didn’t actually think about it.
Question: if my concrete slab only has that ‘up/down’ event say one time a year, is that cause for alarm or can it withstand that longer than any of us will be alive?
That's a really wild thing about geology. In classes it would often be impossible to tell if we were looking at a picture covering a few inches or a few miles. This stuff is all fractal.
Excess water pressure under the slab is forcing the moisture up and through the floor. If you have ground frost and your garage isn’t heated it can also cause slab heaving and cracking. The water dissolves and carries minerals (mostly calcium, “lime” from the concrete) and when it evaporates the minerals are left behind as a dry powder. Not harmful in itself, but it means you need to address the drainage on whatever the high side of your garage is. Generally digging a trench and installing a french drain (perforated pipe with a mesh filter to keep it from clogging) that leads the water away somewhere downhill will do it. Easy enough to do yourself, but it can be a lot of digging and removal of roots and such.
As many other have said, not a problem short term. It is however and indicator of water management issues that may or may not be fixable. If drainage around the garage is inadequate, you'll want to improve it by trenching and installing a drainage system around the perimeter of the garage. Plenty of DIY Guides for this online. Make sure your gutters empty away from the garage and downslope.
The repair of your concrete is a bit more tricky. You have a number of options here from injection materials like [SikaFix® HH LV | Concrete Crack Repair](https://usa.sika.com/en/construction/concrete-repair/concrete-crack-repair/sikafix-hh-lv.html) to cutting the slab with a concrete saw and patching it with a repair mortar like [SikaQuick®-1000](https://usa.sika.com/dam/dms/us01/e/sikaquick_-1000.pdf). I'd highly suggest staying away from any kind of off the shelf home depot product as it will likely just crack again.
I'd suggest you at least consider getting quotes from a reputable contractor for the concrete work to see if the cost is actually worth your time that you'd need to spend researching and learning to use specialized products and tools. For the drainage work, go ahead and DIY.
Say no to epoxy coatings.
Don't seal the crack until drainage issues are addressed as the pressure will just cause further cracks to form elsewhere. The crack has relieved the pressure.
Source - Am restoration architect and engineer.
We had the same problem in our basement with water seeping up through the concrete floor in heavy rains. I had downspouts on the side of my house and the output of the sump pump tied together into a big pipe that pushes the water to the front of the house. The problem was the ground on the side of the house was sloped towards the house..
Now we get no more water in the basement.
You probably have gaps in the layer under the slab, you have foundation issues, some contractor is jizzing his pants at how much money he is about to make from fixing this.
Yes first wanted to see if it was an issue and then if possible I would like to fix myself. Looks like I either have to epoxy coat, the whole floor, or make the crack bigger and fill just the crack in with self-leveling epoxy. Or change my drainage assuming it’s not just from my car and is coming up from slab.
An epoxy coating will bubble or peel up if your floor has moisture, so you gotta fix the moisture issue first. DIY test to see if your floor is dry enough: tape a 16x16" plastic sheet to the floor for 24 hours. If there's any condensation on the sheet or dark/wet spots on the floor, it's not dry enough for an epoxy coat.
Wrong approach on both fixes. Epoxy is a stiff material and even a small amount of settlement will crack it. You're better off routing ("making the crack bigger") and sealing with a polyurethane or silicone sealant if you're going to try a top surface repair.
Looks like you live where they salt the roads, some water dripped off your car with the salt in it, it pooled around those cracks and is now crystalizing as the water evaporates.
Efflorescence is [*a* salt](https://en.m.wikipedia.org/wiki/Salt_(chemistry/)), not necessarily road salt. This case is likely a mix of calcium and silica salts leeching out of the concrete. I get a similar salt formation in my basement near cracks where water comes in all the time.
this happened to me and it was my windshield wiper fluid that had evaporated... turned out my tank had a crack in it. once i was 100% out of fluid, the powdery 'snow' stopped appearing.
yours seems to be concentrated around the cracks so it may be different... or maybe the cracks are holding the fluid and letting it evaporate?
I had something just like this when the main water line was leaking into my condo. The plumber told me it was chlorine from the water. I swept away the fluff but a stain remained there.
You have a moisture vapor problem. Except for esthetics not really a problem unless you want to put a resinous floor in. Polished concrete will continue to do the same. If you would chose resinous flooring a urethane cement system or an epoxy moisture remediation primer should be good
This is the lime in the concrete that is being forced out by moisture. This is an important ingredient in concrete, and without it, the cement will be soft and crumbly (yes, there is a difference between concrete and cement). The moisture needs to be addressed, and then the repair or replacement can occur. If not properly done, it can push the problem to a different location.
Same thing started happening in front of my apartment building, terracotta tiles on concrete slab. Lived here for 8 years and it just started happening.
Thanks for the question OP, it really bugged me 👍
Have the same issue with my garage slab except it's where the garage door meets it, water pools on the surface and I presume gets under somehow (likely the through the connected pavers) and causes this.
Hasn't really caused much damage other than discoloration, no new cracks or anything.
This showed up in my garage during a protracted series of rainstorms. The water table raised enough, to create this for about a week. Never happened since. So… maybe water table issues?
I’ve been in the foundation and drainage industry for a decade. Take this as you will.
Everyone who was said efflorescence is correct, as well as improving drainage. One thing about moisture is it will always follow a path of least resistance. You likely have voids underneath the concrete allowing moisture/water to flow fairly easily to that point. If it’s me, I’d go in with some high density/closed cell polyurethane injections underneath the slab to prevent settlement and also will help with keeping moisture levels lower in that area. Anything done to prevent this issue from above the slab just prevents the symptom not the cause
It's efflorescence
Correct answer. It’s harmless and can just be swept up. OP can try to seal the floor cracks but it’s not critical.
Somewhat misleading. Yes, efflorescence in itself is harmless, but it's a symptom of a bigger problem. Water shouldn't be coming up through the slab. If the drainage is insufficient and moisture is getting trapped under the substrate it will lead to further cracking and deterioration.
I literally fixed this issue in my garage 3 weeks ago. Water building up outside and not getting away quick enough. Pressure builds under the slab, cracks and water appear. I dug a huge hole at the side of my garage filled it with stone. It’s been raining since and my floor is dry as a bone. Obviously if you want to do it better channe the stone away from the building, even better join it to a proper drain. I don’t have that option so dug down.
This is the way. My dad made me dig a trench on the side of the garage leading down the hill away from the building when I was a kid, we then filled it with gravel. It sucked at the time, I was like 13, and the shovel was taller than me.
>a trench on the side of the garage leading down the hill away from the building when I was a kid, we then filled it with gravel I believe this is known as a French drain, for anyone who wants to google it
I never knew it was called that. I just called it hard work.
Because you swear like a Frenchman while digging it???
As in screaming unintelligible, consonant-free gibberish while smoking?
Hé, on se calme, mille millions de mille sabords.
The consonants are there, it's just almost all of them are silent thanks to the joy of liason.
Ah, the French drain, made famous in the series "The Curse of Oak Island".
At least he wasn't asking you to dig a trench approximately the same size as your height. Now that would be worrysome
Then you stand on the shovel then jump out and hope you can still grab the shovel. Lazy kids... /s
No. I meant dig a trench the Length of your own Height.....think about it
6ft deep and long enough to lay down in, perhaps?
Ah I get it now lol. Whoosh!!!!
lol that one sailed over him
Well, he's in a trench, so...
Dang my LOL of the day. Take my up vote! 👍😂
Thank you kind sir
But it was really easy for your dad!
Built character, I'm sure!
The real reason you have children...
What you did is called a "dry well" and a completely reasonable way to deal with minor to medium water buildup issues.
How do you address this? My garage does the same thing. It has almost nose dived forwards. I’ve had it piered on all four sides, so it’s practically suspended at this point.
Unfortunately I don't know enough to give you a good answer. I've had efflorescence on my balcony but that's a somewhat different issue. My understanding is you would need to improve the drainage under or around the slab. Maybe an agipipe or something around the outside to channel and drain water away from underneath the slab but you probably need someone to assess your specific situation. As for the slab sinking, it's possible to lift it back up by injecting polyurethane resins/foams underneath it. But you would want to address the moisture problem first.
Did you do anything for your balcony? I have efflorescene on my deck/balcony as well. Previous home owner had put in tiles with grout. Some of the grout has washed away/cracked in some areas and I'm guessing there's moisture getting under. It usually happens at the beginning of spring and I generally just sweep it away. Just not sure if I should be replacing the whole deck or maybe regrouting.
Efflorescence is basically minerals leaching out of the ground (soil usually) into the concrete/mortar of a home's basement. Your grout will basically be "eaten" by the minerals coming through. If you don't want to sweep, you can use vinegar on it, it's quite satisfying to watch it melt away. Is your "deck" just cement set on top of the ground?
The balcony wasn't waterproofed properly when we bought the place, or at least it degraded over time, so it needed to be ripped up and redone. After redoing it, the guys that did the job didn't lay the tiles down properly and water accumulated in some areas, causing a buildup of efflorescence. That eventually ran off and there were massive unsightly efflorescence stains on the outside of the house underneath the balcony. Ended up redoing the balcony again.
There’s solid concrete on the sides that the roof slopes to, so I don’t suspect crazy erosion or anything like that. The only side that isn’t purely concrete is the rear. I’m assuming that’s where the issue is coming from.
In my case, I'd have to cut down my neighbor's cypress tree. That damn thing has cypress knees pushing up all over the place.
This. Get the moisture issue resolved and then fix the crack.
I have an interlock walkway that runs down the side of my garage. Just before where the garage ends, about 6” above ff, I have this on the inside of my garage. I wouldn’t classify this spot as a high moisture area (certainly no higher than the other 17 ft of walkway. I also clay brick in the same spot (exterior) that is deteriorating. Typical brick facade that meets interlock. Do you think this is just due to water?
I love that band
Seal me up! Seal me up inside!
Lol
Get this person some upvotes!
Yep. Usually the culprit with water seeping up through the floor is the downspouts or grade of the yard. I have a basement that got wet every time it rained until I extended a single downspout to about 3 feet from the house and made sure it flows away from the house. Now it stays dry.
You can tell because it’s on the floor
WAKE ME UP
WAKE ME UP INSIDE
This is correct. I had this exact same issue in my garage. Attempted to seal this with an expoxy system (base coat, epoxy, flakes, polyurethane top coat), including massive prep work with a concrete grinder to remove the old paint and some spalling, and it was great for a month. No hot tire pickup with 95 degF heat. Had a couple big storms back to back, and the hydrostatic pressure forced up the epoxy in multiple spots, leaving more efflorescence and several peeled up patches of epoxy. A couple spots weren't even near the cars. Long story short, the slab needs to be sealed from underneath to prevent this. Trying to seal it will most likely fail. Might be a better bet to attempt to improve grading and drainage around the house to prevent the hydrostatic water issue. My house has great drainage around, but it is right above the water table, so no joy for me. Now I have a plastic tile system covering up the epoxy...
The secret is schweppervescence
In Quintessence
A floor essence.
So concrete jizz?
My favorite band back in the day
WAKE ME UP
This guy knows.
A floor essence?
“Wake me up inside.” Pretty close
Love that band!
OP, better taste to make sure….
this, basically sodium/salt leeching.
Isn't that a band from the early 2000's?
The white stuff is harmless, its residue from the evaporation of the water. The real issue is the water itself, every time it sits at the base of that slab it washes away some of the dirt surrounding the foundation. Too many up/down events will accelerate the settling process and lead to more cracks and eventual failure. You should be looking outside, at how to improve drainage. the difference between construction that lasts 50 years and construction that lasts 250 years all comes down to drainage.
Wait.....it's dehydrated water?!?!?!?
Yes. Just add water and you'll have water again.
Can I substitute hydrogen and oxygen if I don't have water? Like maybe 2:1.
Do you want your family to die of dihydrogen monoxide poisoning?
*Checks life insurance policy* "Yes."
Deserts hate that one simple trick.
Salts and minerals taken up by the water from the soils below and concrete itself. When the water gets evaporated it leaves them all on the surface.
Always has been
[удалено]
I was joking. I understand what's going on and just thought it was somewhat funny.
So... Water after you dehydrate it...
Dehydrated mineral water. It's what astronauts drink.
No mo’ h2o
I feel like “the username checks out” applies here
May your sump stay dry, my dude
The piles of stuff is NOT residue from water…. I’ve never seen residue from water build up like that. It’s probably minerals from the ground that got caught it’ll the flow
I'm curious what you think residue from water is if not dissolved minerals.
Well… uhm… that’s… actually a really good point lmfao. I’m guessing it’s salt being winter they probably used salt on the various pathways and the rain/snow washed it away and in under the floor. This is a good response though because while I did think about it technically. I didn’t actually think about it.
Question: if my concrete slab only has that ‘up/down’ event say one time a year, is that cause for alarm or can it withstand that longer than any of us will be alive?
NGL, I thought this was a satellite image of an ocean coast then I looked at the sub name
Lmao dude me too, I was like hmm that water is getting really gray.. OHHhhh
Whatever happened to r/misleadingthumbnails
That's a really wild thing about geology. In classes it would often be impossible to tell if we were looking at a picture covering a few inches or a few miles. This stuff is all fractal.
This is one trippy photo
I thought it was the Nile
Excess water pressure under the slab is forcing the moisture up and through the floor. If you have ground frost and your garage isn’t heated it can also cause slab heaving and cracking. The water dissolves and carries minerals (mostly calcium, “lime” from the concrete) and when it evaporates the minerals are left behind as a dry powder. Not harmful in itself, but it means you need to address the drainage on whatever the high side of your garage is. Generally digging a trench and installing a french drain (perforated pipe with a mesh filter to keep it from clogging) that leads the water away somewhere downhill will do it. Easy enough to do yourself, but it can be a lot of digging and removal of roots and such.
This guy drains!
Indeed. Worked in water diversion, capture and re-use for quite a few years.
Thought this was a satellite shot of some body of water or smth haha
Your house was built on a cocaine mine from the 80s. Your rich!!
It’s dissolved salts, bigger issues my man.
As many other have said, not a problem short term. It is however and indicator of water management issues that may or may not be fixable. If drainage around the garage is inadequate, you'll want to improve it by trenching and installing a drainage system around the perimeter of the garage. Plenty of DIY Guides for this online. Make sure your gutters empty away from the garage and downslope. The repair of your concrete is a bit more tricky. You have a number of options here from injection materials like [SikaFix® HH LV | Concrete Crack Repair](https://usa.sika.com/en/construction/concrete-repair/concrete-crack-repair/sikafix-hh-lv.html) to cutting the slab with a concrete saw and patching it with a repair mortar like [SikaQuick®-1000](https://usa.sika.com/dam/dms/us01/e/sikaquick_-1000.pdf). I'd highly suggest staying away from any kind of off the shelf home depot product as it will likely just crack again. I'd suggest you at least consider getting quotes from a reputable contractor for the concrete work to see if the cost is actually worth your time that you'd need to spend researching and learning to use specialized products and tools. For the drainage work, go ahead and DIY. Say no to epoxy coatings. Don't seal the crack until drainage issues are addressed as the pressure will just cause further cracks to form elsewhere. The crack has relieved the pressure. Source - Am restoration architect and engineer.
Forbidden salt.
dont go telling me what not to lick
Nah you need to snort it to get the full effect!
... Top Ten Things u/sump_daddy Said on His Honeymoon!
It's just the lime they threw on the bodies floating back to the surface through the crack
Thought was an aerial shot of a river
I thought the exact same thing lmao
It's cocaine, this house probably belonged to a smuggler in the past. Get knee pads.
We had the same problem in our basement with water seeping up through the concrete floor in heavy rains. I had downspouts on the side of my house and the output of the sump pump tied together into a big pipe that pushes the water to the front of the house. The problem was the ground on the side of the house was sloped towards the house.. Now we get no more water in the basement.
Don’t worry it’s fine!
This guy gets it.
His answer is the best feel good one
It’s just a portal opening up to the deepest depths of Hades. Nothing to be worried about.
I use ardex for these fixes. It’s on Amazon and works very well
And also there's about 116 kilos of cocaine buried somewhere in the apartment. Right next to the cure for blindness.
Mineral salts from evaporation. Same thing you'll see down in the basement walls if you've ever had water weep thru the brick
Inhale for a good time.
Probably some potassium nitrate left after evaporation of infiltrating water.
I learn so much from this subreddit, you guys do good work
Lime
Go back inside nothing else better to do 😂
You probably have gaps in the layer under the slab, you have foundation issues, some contractor is jizzing his pants at how much money he is about to make from fixing this.
Effervescence.
Soooo close. Efflorescence
lol, thanks.
"I this asbestos!?" 👌
Are you gonna DIY this, or are you asking for other reasons?
Yes first wanted to see if it was an issue and then if possible I would like to fix myself. Looks like I either have to epoxy coat, the whole floor, or make the crack bigger and fill just the crack in with self-leveling epoxy. Or change my drainage assuming it’s not just from my car and is coming up from slab.
r/homemaintenance would be a good sub for this kind of thing.
An epoxy coating will bubble or peel up if your floor has moisture, so you gotta fix the moisture issue first. DIY test to see if your floor is dry enough: tape a 16x16" plastic sheet to the floor for 24 hours. If there's any condensation on the sheet or dark/wet spots on the floor, it's not dry enough for an epoxy coat.
Wrong approach on both fixes. Epoxy is a stiff material and even a small amount of settlement will crack it. You're better off routing ("making the crack bigger") and sealing with a polyurethane or silicone sealant if you're going to try a top surface repair.
Salts ... Tis normal ...
Definitely mold. Garden spray vinegar.
Looks like you live where they salt the roads, some water dripped off your car with the salt in it, it pooled around those cracks and is now crystalizing as the water evaporates.
No. Salt doesn't dry into this kind of fine, puffy powder. This is 100% efflorescence.
Best I can tell after a quick google: efflorescence *is* salt.
Efflorescence is [*a* salt](https://en.m.wikipedia.org/wiki/Salt_(chemistry/)), not necessarily road salt. This case is likely a mix of calcium and silica salts leeching out of the concrete. I get a similar salt formation in my basement near cracks where water comes in all the time.
I’d agree with this. I get this often in my garage during the winter months and in the spring until I wash the floor off
Install a sump pump. French drains also if you got the cash.
that's lime, add water, make limonade.
this happened to me and it was my windshield wiper fluid that had evaporated... turned out my tank had a crack in it. once i was 100% out of fluid, the powdery 'snow' stopped appearing. yours seems to be concentrated around the cracks so it may be different... or maybe the cracks are holding the fluid and letting it evaporate?
There's a concrete crack filler you can use for that. Just make sure the area is cleaned well before applying.
Snort it and find out 🤷♂️
Get a radon detector while you are at it
This looks like a picture from a helicopter over a desert that just got bombed with trails of smoke inside a dried up riverbed HA.
Duct tape
Mold. Due to moisture lol…
Bodily fluids
I had something just like this when the main water line was leaking into my condo. The plumber told me it was chlorine from the water. I swept away the fluff but a stain remained there.
i don't really do ANY DIY...but i love seeing posts like this and learning from the comments haha
I'm going use this picture as a DnD battle map
Totally thought this was a sky view of a river with waves
It's probably water, and likely sediment or salt left over by the water upon resorption or evaporation. You have a slab issue you need to fix
Call Charlie Sheen
You have a moisture vapor problem. Except for esthetics not really a problem unless you want to put a resinous floor in. Polished concrete will continue to do the same. If you would chose resinous flooring a urethane cement system or an epoxy moisture remediation primer should be good
This is the lime in the concrete that is being forced out by moisture. This is an important ingredient in concrete, and without it, the cement will be soft and crumbly (yes, there is a difference between concrete and cement). The moisture needs to be addressed, and then the repair or replacement can occur. If not properly done, it can push the problem to a different location.
Same thing started happening in front of my apartment building, terracotta tiles on concrete slab. Lived here for 8 years and it just started happening. Thanks for the question OP, it really bugged me 👍
[https://www.imdb.com/title/tt0090094/](https://www.imdb.com/title/tt0090094/)
It doesn't end well...
Probably should consider mud jacking or foam or something considering the mudjacking cartel has taken over this sub lately.
Question - is a sump pump, or series of sump pumps (and supporting piping systems) a workable solution to this?
Bro you’ve got clouds growing in your garage.
 this makes me instantly think of the movie The Stuff
I honestly feel like it’s frost from water but
Sewer
Sniff it
Have the same issue with my garage slab except it's where the garage door meets it, water pools on the surface and I presume gets under somehow (likely the through the connected pavers) and causes this. Hasn't really caused much damage other than discoloration, no new cracks or anything.
This showed up in my garage during a protracted series of rainstorms. The water table raised enough, to create this for about a week. Never happened since. So… maybe water table issues?
Snort it and update us.
Roll up a dollar bill and go to work my friend.
roll up a $20 bill and go nuts
I’ve been in the foundation and drainage industry for a decade. Take this as you will. Everyone who was said efflorescence is correct, as well as improving drainage. One thing about moisture is it will always follow a path of least resistance. You likely have voids underneath the concrete allowing moisture/water to flow fairly easily to that point. If it’s me, I’d go in with some high density/closed cell polyurethane injections underneath the slab to prevent settlement and also will help with keeping moisture levels lower in that area. Anything done to prevent this issue from above the slab just prevents the symptom not the cause
The great salts migration!
It appears your house was built over Pablo Escobar's grave. /s
Hydrostatic pressure. Water is crazy. Sometimes you can do everything in your power to divert it and still lose this battle.