Concrete Crack Repair

[kennyb04]

I have read through some other threads on this subject but want to verify a couple things. We have some cracks in a truck bay/garage forming from the corners of the floor drains. Our concern is not with the actual cracks or how they formed (We have a couple ideas why but that isn't the point of this post). For the the most part, they are really just cosmetic.

This is a garage bay where trucks will be washed inside in the winter so there will be a decent amount of water on the slab and there is a radiant heat system in the slab as well. We plan to seal the cracks with an epoxy system and want to know the best approach. I have looked at Simpson's Crack-Pac system and also saw some information on a thread about Sikadur33. Does anyone have a preference on which to use, or any other product. Is there a product that would be best for keeping water from getting down in the cracks (that is one of our main conerns right now). Is there any certain finish that should be used after the epoxy system is placed in the crack? Thanks for any input.

Also, are there any good resources for crack repair for SOG? Does ACI have anything? I know a lot of cracks are cosmetic and are within acceptable range (as these probably are as well). But as previously noted, we are wanting to seal them because of the amount of water they will see.

 

[kennyb04]

Another photo

 

[TXStructural]

Talk to your local Sika or other manufacturer's rep. The usual method is to chase the cracks with a grinder, to create a continuous groove of sufficient width. You should look for a material which has a bit of elasticity, so the you will have less maintenance as the concrete moves. Even slight movement along a crack filled with rigid filler will result in a new crack.

If you believe the crack is relatively stable (if it originated from drying or other early age shrinkage), then you could consider epoxy injection to "glue" the slab back together. This would be done by a repair contractor, and is a long term solution. This can be combined with the more attractive top seal if you prefer.

Avoid grinding the flat surface of the concrete. Your slab appears to have a good, hard troweled surface that will be more durable than a ground one.

 

[MiketheEngineer]

Call the "Crack Team" - a local vendor that does only concrete cracks

 

[hokie66]

I would use epoxy injection. These cracks are caused by the stress riser at the reentrant corners as the concrete shrinks.

 

[KateP]

hokie66,

Let me to understand You: cracks in the slab (in this case above) are caused by shrinkage of concrete?

 

[hokie66]

Yes, the concrete shrinks, goes into tension due to restraint, and the reentrant corners cause cracking to occur at that location. It is good practice to require diagonal reinforcement at these penetrations.

 

[Ron]

Agree with hokie66. Shrinkage cracks at re-entrant corner condition. I've used Sikadur 33 numerous times with good success. Get someone experienced in structural repair with epoxy injection.

 

[hokie66]

I concur with the use of Sika products for concrete repairs, although there are other excellent suppliers. There are many Sika products which might apply...Sikadur 33 is in a paste form... something like Sikadur 52 would probably be used for the low viscosity injected material, with the paste used to fill the injection ports.

 

[KateP]

Thank You for explanation (the 'tension' was the key)

 

[hokie66]

You are welcome. Concrete doesn't crack because it shrinks, rather it cracks because it is in tension.

 

[SLTA]

Given that the floor will have a ton of water on it, you may want to look into an overall epoxy floor sealant, especially if there's salt involved in what gets washed off the trucks. I thought of those "garage sealer" ads in car magazines, or perhaps something as hardcore as what they use to seal floors where nasty chemicals are involved.

 

[kennyb04]

Thanks for all the replies. Ron, you mentioned Sikadur 33. This is a paste, correct? Will Sikadur 33 work on smaller cracks or should something like Sikadur 52 with a low viscosity be used?

I also noticed Sikadur 33 and 52 are in the structural injection section. There is also a section for waterproofing injection and includes SikaFixHH+ and SikaFixHH. Is there much of a difference between the structural injection and the waterproofing injection? Since we don't have a structural slab (it is SOG) would one of the waterproofing injection products be better? Our primary purpose for repairing the cracks is to keep water from getting into the slab, especially if any salts are washed off trucks in the winter time. We want to avoid though resealing the entire floor. I don't feel that would be necessary at this point. Does anyone know if any of the waterproofing injection products are less rigid than the structural injection products?

I plan to call a Sika person about these questions too but would like to hear opinions from any of you as well, thanks.

 

[MiketheEngineer]

Just remember - Concrete always cracks and will ALWAYS crack -- no matter what you do!!

 

[Ron]

Sikadur 33 has been available in the past in a couple of forms...apparently now it is only available in its paste form. For crack penetration, you might consider Sikadur CrackFix...it is the same as Sikadur 35 and will gravity flow into cracks.

Here is the approach I would use to fix the cracks....

1. Route the surface over each crack to a depth of 1/2 inch and 3/16 to 1/4 inch wide.
2. Gravity flow Sikadur 35 or Sikadur CrackFix into the crack. Allow to penetrate.
3. Fill the routed area with Sikadur 33.

 

[TehMightyEngineer]

I'd just contact Sika on which product to use and follow their specifications and details. I recently contacted them about a custom expansion joint and they were quite helpful.

You also mentioned early on if ACI had anything on this. The short answer is, yes, they have the concrete repair manual but I'd say that the crack sections simply boils down to "follow manufacturer recommendations for epoxy injection".

Maine EIT, Civil/Structural. Going to take the 1st part of the 16-hour SE test in April, wish me luck!

 

[AlbertStructural]

Hi kennyb04,
I can name another very famous supplier and that is Fosroc. Their product is Nitofill EPLV and is an excellent crack filling epoxy compound. It will permanently seal the cracks. You can do gravity pouring after cutting a groove of about 15-20mm width and 25mm deep. For more info refer to their online datasheet of the product.