You're concerned because it's still that darker colour of grey? Looking like it's moist? I would say in 2 weeks I've seen some concrete still have that green (wet) look to it. It could also just be a different concrete mix/different aggregate is causing a different colour. Some of those bag mixes I've used have an extremely dark natural colour to them.

Is it hard when you press on it with a screwdriver? If so, I wouldn't worry about it too much if you're confident you have no plumbing leaks or source of water below the repair area. If there is a source of water below, you'd want to find out what's causing it, but it's affect on the concrete should be your least concern.

Why does photo #1 show what looks like dirt below the pipe whilst photo #2 shows crush??? What part of the construction sequence have you not documented??

@jayrod12
I am concerned with the fact that it feels wet
In one of the pictures you could guess a hair dryer that I used to dry up the patch -it turns lighter but then after a while it gets back to darker
and it forms that white efflorescence, so I am not sure if it still cures and it still dries up after so long or there is something else. Se my next comments for miningman

@miningman
As someone advised I added some gravel there to break the humidity propagation. That is why you see gravel in the second picture
Now having that gravel layer should prevent the humidity from ascending toward the surface and my wet like looing patch should dry up.

In beginning I suspected the curing concrete cracked open the cemented joins and I had a leak at the bottom end of the elbow
So I made sure that no water is flowing through the pipe anymore (I had just the condense pump from my furnace pumping like 1 liter of water once or two times in 24h. SO I disconnected that but the patch still feels wet and if I dry it up with a hair dryer it gets wet like

Don't get me wrong the concrete is rock solid but it does feel a little bit wet -leaving a piece of tissue on top of it hardly collects any humidity but I still see that efflorescence forming

To be fair, you did use a product intended for post fixing, so you shouldn't expect visually appealing concrete. Some concretes take long than others to fully cure and use up all of the water.

The visual aspect is not a problem, the possible ascending humidity could be
I plan to pour a layer of self leveling concrete on top of what you see so I can install tiles

The ascending humidity would be an issue regardless of the concrete used. I wouldn't expect that the post fixing stuff is overly different from the general use fast set from a porosity standpoint unless you mixed it significantly different.

I understand that you're likely in a time crunch, but I'd be leaving that area as long as possible to allow it to dry as much as possible prior to installing the leveling compound and tiles.

Not in a time bond, I can wait as long as needed we have two bathrooms
Is there any technique I can use to accelerate the drying up process?
I also cant make sense of the difference in behaviour regarding the humidity for the two concrete types

Still have this question: can the concrete, while it is drying up, crack an ABS join that it is cast in the respective concrete

Hope I am using the right terms here

Post hole concrete pre-mix has a bit lower cement content. Definitely more permeable that a 4,000 psi mix. About $2 extra per bag, just to rub it in.
However, you might have a moisture problem, and you need to figure out the source before proceeding.
Drill a vertical hole or two through your new concrete, and before you apply a cementitious topping for observation. Make sure there is not positive pressure. Even if you tile over concrete that have positive pressure behind it, it will probably continue to give you problems.
At the end of the day, water always wins.

I wouldn't say the curing process for the concrete should of affected the pipe at all. If it did, this would be the first time I've ever heard of that.

However I was at a house recently where a joint on plumbing below a slab wasn't glued. It had been dry fit up and no one went back and glued it together. Slow leak caused heaving of the subgrade (where I am our subgrade is highly susceptible to volumetric changes due to moisture content) to the point that there's a 5" tall 10 foot diameter cone of heaved concrete slab right above the plumbing joint.

@jayrod12 -I tested (no pressure testing though) the joint for leaks
The ABS cement is visible for each join if I zoom in in the first picture

@ATSE what is a sign that I have positive pressure there, sorry I am not familiar with the terminology
I am quite sure the humidity gradient is from under the slab toward the floor surface and into the room there is no question about that
How come the other path of concrete is not experiencing the same issue ?

One detail that is worth mentioning is that the humidity of the dirt in that opening changed over time
It stayed dry in the winter and it was a little bit more humid when the temperature raised (I live in Toronto)
I had to dig the dent to make room for the P trap and you can see that in the first picture; no water was observed during that time
The next day after the day when I finalized the dent to make it deep enough I could see some water collected in that gap
This also coincided with a very heavy rain (I think it rained the entire night)
Once the P trap was in I added dirt back to set the surface level and then I added gravel
However as you can see in the picture the space above the P trap was not sealed and it can bread so if any more water accumulates there I should see humidity or water around he drain where the gravel is visible. That spot is marginal to the entire wet areas

That is an obscene amount of water ponding only 6 inches below your concrete surface . Strongly suggest having a local contractor look at the area and making corrective suggestions. My guess is it will require extensive and expensive drainage before any more concrete is applied.

After removing that water it went away and it did not collect again
It was a one time since August since I opened that area and my guess is that it collected there because it was the lowest point and it percolated from the area around it.

Quote:

Is there any technique I can use to accelerate the drying up process?

Probably, but that would interrupt the hydration (curing) process of the concrete, so it would not continue to gain strength like it's supposed to. The specified strength of the concrete is at 28 days of age. Granted, after 2 weeks it's probably 80-90% to that full strength, it's still curing and should be expected to still feel moist, and it's a good thing, since that helps the curing process.

Rod Smith, P.E., The artist formerly known as HotRod10

I am in no rush but the other section is dry like Sahara...

Concrete patches are nearly always ugly... just be careful what you paint it with...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

I will pour self leveling concrete so I can install tiles and a shower base that needs to be level

Not sure what the plan is, but if you're using self-leveling concrete (or any mixture with actual cement) over the patched area, you don't have to wait until it's dry. It actually bonds better the sooner you do it. Concrete doesn't 'dry'; it cures by hydrating (growing intertwined crystals from dehydrated mineral). Therefore, a better bond between new concrete and old is achieved when the old concrete is in a condition called saturated surface dry (SSD), where the old concrete itself is as moist as it can be, but there's no water on the surface. So, your best approach, short of actually roughing up the concrete surface, is to keep the concrete wet for a few days before applying the self-leveling concrete, but be sure you keep any water off the surface for a few hours before pouring.

Rod Smith, P.E., The artist formerly known as HotRod10

You have to be careful... best to encapsulate the stuff in gravel and add concrete over... if the concrete moves and the stuff is inside, it may cause it to break.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

As Bridgesmith stated, concrete does not dry, it cures. Concrete gets hard through a chemical process where the water reacts with the cement. If you don't have water you won't have a reaction, if you have too much water you will have excess water that will evaporate (causing excess shrinkage). Concrete will develop the most strength buy curing in 100% humidity (no loss of water that would have been needed for the curing process due to evaporation). Using a blow dryer to "dry" the concrete will simply result in evaporating water quicker than it would naturally and possibly removing the water that would have been required for the chemical reaction (i.e. reduces the strength of the concrete). It would also increase shrinkage - probably not a problem for a patch so small.

Why does your concrete patch appear so brown? Did you mix the concrete with water in a separate then place it? Or did you just pour the powder mix into the patch and ad water to it (I see this done with fence posts, but it results in a inferior product)? The brown appearance makes me think there is a bunch of dirt mixed in with the concrete (which is why I ask how you mixed it), which would certainly have negative effect on the final product.

No the concrete was mixed in a bucket, clean, no dirt there, maybe some leftovers from the previous bag (see the pictures)
this concrete mix bag (a half of a bag), was a leftover that sat for 2-3 years in my garage, not sure if this matters


I am not really concerned about those patches collapsing on the gravel that is underneath as this will be under a very sturdy shower base that does not bend even a mm under my 115Kilos weight (tall guy)
I will wait longer for this to cure to see if the color turns grey and it looks dry
Rushing to pour the self leveling concrete now while this patch is still wet does not make much sense as it is just a small portion of the bathroom floor
It is more important for me to make sure I have no problems in that area...so I will wait

Quote (MiniMe4Eng)

this concrete mix bag (a half of a bag), was a leftover that sat for 2-3 years in my garage, not sure if this matters

It matters very much. Most garages are not climate controlled, so if the humidity ever got very high it could have started hydrating some of the cement in the mix, though it could still look viable on first inspection. I have a few bags left over from a fence project from a few years ago, also in my garage. The city frowns on disposing of old bags of concrete in the trash, and my truck is broken, so there they sit. Last month I tried to make a little "slab" that my son could break with a new toy (RC excavator with jackhammer attachment). It did exactly nothing. After a week it just a pile of damp sand, gravel, and itty-bitty pieces of hydrated cement.

Quote (phamENG)

It matters very much. Most garages are not climate controlled, so if the humidity ever got very high it could have started hydrating some of the cement in the mix, though it could still look viable on first inspection. I have a few bags left over from a fence project from a few years ago, also in my garage. The city frowns on disposing of old bags of concrete in the trash, and my truck is broken, so there they sit. Last month I tried to make a little "slab" that my son could break with a new toy (RC excavator with jackhammer attachment). It did exactly nothing. After a week it just a pile of damp sand, gravel, and itty-bitty pieces of hydrated cement

Doesn't seem to be my case, the patch is rock solid

Quote:

the patch is rock solid

Then there's no problem; it's just as it should be. Again, if your concern is putting a cement-based material over it, you shouldn't be concerned. Concrete can be, and is, poured underwater, and as long as it's not disturbed, it cures just fine.

Rod Smith, P.E., The artist formerly known as HotRod10

"Solid" isn't exactly a technical term when it comes to concrete. Just because it has hardened doesn't mean that it isn't excessively porous and prone to wicking water, or especially strong (though strength isn't critical here). When you broke out the slab, was there a vapor barrier below it? If not, have you had issues with elevated moisture in that room before? You clearly have issues with ground water coming up close to grade - I live in a swamp so I get it. In the middle of a drought I can hit water less than 12" below grade. I'd strongly suggest doing some work on the exterior (grading, in-ground drainage, etc.) to move ground water away from your house. And if you had a vapor barrier before, you should have patched it when you put this back. If you have a nice, warm, dry interior and wet soil underneath, that moisture will migrate through the slab, mortar, etc. and into the living space, potentially damaging your flooring along the way.

There was no humidity barrier ther just the concrete. It was even worse than this before, whoever qorked that bathroom effectively left open dirt under the bath tub. I had no issues with extending the openning by hitting the edges of it woth a hammer and the concrete chipped away little by little in a quite cintrolled way.
The house was built in 1960....they did not use to install a barrier back then
The basement has elevated humidity in the summer but I think it is normal. I can keep it under 50% with a dehumidifier that runs every 3h for 1h. That is summer time only...no problems in the winter
The house at the bottom end of a street that goes up on a hill, not very sloped, that could be the only issue here. The grading around the house is fine and on that side I have a patio that is sloped away from the house.

Two months later it is almost dried up

I would assume most of the initial problems stemmed from the large amount of water pooling in the area below the concrete. Sounds like it was just there temporarily though, and it looks like it has dried up now. Great tips and concreting advice from everyone above. Good learnings.
Ashton from The Concrete Cure Toowoomba