Please tell me if this is a good fix

[MarkBlake]

I recently had new concrete installed in my barn that was converted to a 3 car garage. The concrete was in extremely bad shape and I decided to get it replaced. I also added a 3 ft apron. The concrete contractor did a good job excavating and put in what looked like a solid base--stone with vibratory compaction. 5 inches of concrete was poured in all 3 bays in rapid succession. The finisher got started and the winds picked up. It was an extremely windy day and the third bay and apron cured before he could get to them in time. 5 cracks appeared within hours and the concrete was looked over by the plant owner who deemed the concrete was good. The contractor called these cracks shrinkage cracks and he said it was because the wind dried out the top before the bottom cured. He said he was going to treat the caulks so they wouldn't be as noticeable. I said that wasn't acceptable and he said let me figure this out. He finished the work and it looked very good except those cracks. It rained off and on and continued to be very windy. He came back very early the next morning and made control cuts. He called me the day after and proposed the following:
Install pollyaspartic coating over the bay with cracks and entire apron after filling the cracks. I said it wouldn't look uniform, he said he can do the other two bays for cost of materials which he said was 750.00.
I have no experience with this coating and I'm concerned that this is simply a bandaid which will fail and leave me with another nasty looking floor. He will have to grind the trowel-finished smooth floor which also bums me out. The contractor said this is actually an upgrade and will last for 20-30 years. How do you recommend I proceed?
This is a very big contractor with lots of experience installing these floors. He said it would cost 4 grand to do this work usually. Is he blowing smoke?

 

[tonyciambrone]

Well I'm the first here so I will do the obligatory

Post pictures.. links to pictures.. etc.

Hard to judge without seeing the concrete. But, if the cracks in the apron are not major, and you can get your garage coated in a quality polyaspartic for $750.00 uh yeah I'd probably do that. It does cost a lot of money to get a guy to grind your floor and coat it.

 

[MarkBlake]

I don't see any option to attach picture files.

 

[38 Dodge Coupe]

I seem to recall that you need to have a minimum number of posts (10?) before you can can attach pictures, which may be why that option is not showing up.

 

[ConCretin]

I'll leave it to others to comment about the merits of the polyaspartic floor covering other than to note if you don't have a quality vapor barrier under your slab, this might not be a good option.

I am more curious about the sequence of events. What does "the third bay and apron cured before he could get to them in time" mean? Do you mean he was unable to get the concrete finished or not able to apply curing protection? How wide are the 5 cracks? You also mention rain. Was the floor exposed to rain? Were the areas that cracked placed from a different concrete truck than the rest? If we can better understand the problem, we can offer better advice

And, oh yea, the part about the guy from the plant coming out and declaring the concrete is fine by looking at at? That's total BS. If he can do that, he has a bright future in the palm reading business.

Whatever you decide about accepting a topping in lieu of a new floor, you want to be sure the concrete is sound and I think the jury is still out on that. Also, I wouldn't pay anyone just yet.

 

[MarkBlake]

There is a vapor barrier. He just didn't get in there to finish it before it started setting up. The weather change was very extreme and nobody really expected it. The apron was exposed to rain 6 hrs later, floors are under a roof. They're hareline cracks but appear to run the length of the floor ( they're actually multiple cracks) and look exactly like what I see when I Google shrinkage cracks. I paid 1000 less but agreed to pay that plus 750 after coating. I really don't know what to think, he seems honest and is known for good work but these cracks are killing me...

 

[ConCretin]

I'm still not clear. Shrinkage cracks don't have anything to do with whether he got the slab finished or not. Windy conditions can cause surface cracks called crazing but not typically full depth shrinkage cracks while the concrete is still being finished. When exactly in the finishing process did you notice the cracks? Also is there any steel reinforcing in the slab?

 

[MarkBlake]

Within an hr of pour he knocked on my door and showed me them. He said they are surface cracks. He said surface and shrinkage when describing the cracks. It's got steel mesh in it.

 

[ConCretin]

How is the finish on the slab?

 

[MarkBlake]

Very smooth trowel finish. Extremely happy with everything except cracks. That's why I'm hesitant to have it coated... It's such a nice floor already. However I don't have any experience with "pollyaspartic"

 

[ConCretin]

Well after all that I'm not going to tell you anything you don't already know. It seems likely that what you have are called plastic shrinkage cracks.

These are not quite the same as the more common full depth shrinkage crack that result from the overall volume change in a slab. While typical shrinkage crack can be avoided with control joints, plastic shrinkage cracks occur much earlier and are more of a surface crack. They occur under the windy conditions you experienced and are difficult to avoid. They often run the length of the slab a few feet apart.

As you have deduced already, they mostly an aesthetic issue. The presence of wire in the slab will help ensure the cracking doesn't get worse, open up or move going forward.

The cracks would likely have occurred regardless of the timing of the finish but that leads me to another potential concern. How was he was able to achieve a good finish on the concrete if it hardened before he got to it? If he achieved this by applying a lot of water, it could weaken the surface layer resulting in dusting. These is also a risk of de-lamination under these conditions.

Dusting is a weak surface layer caused by excess water and can interfere with adhesion of floor coverings. De-lamination occurs when a thin surface layer is physically separated from the underlying concrete by air and bleed water pooling under a surface that was sealed up too soon. Sections of the surface will peel right off if hit or pulled. Either condition is obviously a problem with or without floor covering.

As i started out by saying, others will have to help you decide if you want the polyspartic. I'd just want to make sure the slab surface is OK to avoid future lifting. Most adhered floor systems require you to wait 28 days. This should allow you the time to asses the floor.

If you want to check, dragging a chain across the surface and listening for a change in tone will identify any de-laminated areas. Dusting will be evident if running your hand across the surface lifts a fine powder. Either condition should be carefully evaluated before applying any kind of floor covering.

I hope I haven't just complicated your decision making process even more but these are things I'd be concerned about before I settled on a solution.

 

[MarkBlake]

Thanks for bringing up all those points. There was a dutch door in the third bay which only had the top half on the hinges, it kind of made the garage into an air duct when the garage door was open. I remember thinking, wow it's really windy with that door half off. Maybe that had something to do with it.
You're right though, time wouldn't really make a difference. He also mentioned he should have put up a wind break. I don't know about the water on the slab--I didn't watch that part very closely. When I came out with him the floor was finished and the cracks were present. Maybe he finished everything and then they cracked? I don't know, I should have asked. This is the first major project we have paid a contractor to do and it was actually more stressful for me than fixing things up myself. I will check for delamination and dusting although if I discover it I'm not sure if I will have any recourse. I figured I needed to decide between a discounted concrete price or a pollyaspartic floor--I wasn't questioning the slab's integrity, but I am now.

 

[ConCretin]

I wasn't questioning the slab's integrity, but I am now.

I wouldn't necessarily assume the worst. A lot of slabs have similar issues. Just something to be aware of.

Your finisher sounds like he has a good reputation and seems willing to make it right. Maybe have a conversation with him about how it went and your concerns.

 

[MarkBlake]

Good advice, thanks for all the information.