Questions Regarding Dark Spots in Concrete

[JoshuaCollins]

Hello all, I am in the middle of an entire home renovation. We chose to do polished concrete throughout our entire first level. We decided to do an overlay on top of our slab. Self leveling concrete was used. There are two spots that have appeared that don't look like the rest of the flooring. Is anyone able to diagnose why these spots could have appeared? O

r better yet does anyone have a solution to fix these two spots?

 

[Floorist]

Isn't that a crack?

 

[JoshuaCollins]

I am pretty sure it is not a crack. I'll add another photo so you can see the other spot. Do you have any idea what it might be if it isn't a crack?

 

[highup]

How large of an area was done in self leveler? Did they use a pump truck? If mixed in single bag batches, maybe it wasn't mixed well enough.

 

[JoshuaCollins]

About 1,00 sq ft were done in self leveler. They had large buckets and were pouring it into the floor while other guys smoothed it out.

The concrete sub said it could be the way it reacted with the slab. That didn't sound accurate to me, however, as it seems like if that were true it'd be happening all over. And there are only two spots. Are you buying that explanation?

Either way, I just want it fixed before I finish paying. Do you know how this could be remediated?

 

[highup]

To me, fixing would mean starting over.... Hammering it all out and repouring.... or adding another layer.
A pump truck probably would have mixed the leveler more consistently and blended many bags at a time as opposed to two bags at a time. That would have been very expensive unless someone in your town already has one.

 

[highup]

A pump truck could do a continuous pour.
The self leveling mixtures most flooring installers use don't need to be pretty, just smooth and flat.
Maybe concrete staining could be done. It could add a little warmth to the floor and maybe hide some of your problems.

 

[highup]

What product did they use? Maybe you should contact a tech person from that manufacturer. Show them the images an get their input.

 

[JoshuaCollins]

Thanks for the feedback. They're two relatively small spots. Would it be a nightmare to just jackhammer those two spots out and re-pour?

 

[highup]

I wouldn't think it possible to repair a single spot or area. I'd really check with a tech guy at the company that manufactured the stuff.

 

[Bogdonovich]

Moisture or poorly mixed material

 

[Incognito]

Moisture or poorly mixed material

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Those are going to generally speaking be the first, and most likely suspects. Down the list but right there on the list is the PREP and application of PRIMER. So many variables here........consistency of the substrate condition (bond and porosity) is controlled by cleaning/scouring, shotblasting, sanding, abrading, vacuuming. ANY contaminate on that slab, like for instance if someone spilt a cup of coffee on the slab/ply it would affect how the primer and self-leveling set up. Frequently, the existing slab has all kinds of floor patch, glue and whatnot that needs to be properly removed or encapsulated.

Keep going on the list? Water quality in the batching, Water quantity in the mix, consistent mixing time and RPM, temperature, humidity, ventillation...........so many variables!

Those aren't great photos and we can't see the rest of the work and how this contrasts. I've alway's found it difficult to capture this sort of thing on film (digital). Sure looks like a crack to me.

It's not rocket science. It's floor(covering) science. I would want some sort of stain/color/texture planned from the getgo to conceal or absorb expected inconsistencies in the finish. Certainly some surface treatment could be applied to blend over that small glitch.