Self-leveling polymer-modified concrete overlay?

[TDabney]

Hello,
I'm looking for additional guidance on dealing with the concrete slab floor in my (new to me) shop. The slab isn't in as bad a shape as the one in this recent thread: http://www.garagejournal.com/forum/showthread.php?t=192322 but I haven't completely ruled out removing it and pouring a new one either.

The floor is about 1,100 sq.ft. and divided into 6 separate squares. It's big enough that removing it and pouring a new slab is not a trivial expense and big enough that tiling is significant $$ too.

To start with, it was filthy, so I started another thread about cleaning it here: http://www.garagejournal.com/forum/showthread.php?t=191010 ... I spent an entire day with a pressure washer and a few different detergents cleaning and scrubbing every sq. inch, with poor results - I barely made a dent in the oil/diesel/grime stains.

So last week, I paid to have it ground down. My hope was that by having it ground, a lot of the oily, stained top layer would be ground off and the process would also help flatten the high/low spots. I also was thinking that it would be a necessary step anyway if I decided to do an epoxy coating. The end result - It was quite successful in cleaning the stains, but less successful in leveling the high/low spots.

So as it sits now, visually, the ground concrete is 100% acceptable to me. What is still a concern is the waviness - there are many high/low spots with maybe the worst dip being almost 1/8" plus or minus. These are not gradual, but can be found with a 6' long straight edge. I feel like that it's JUST bad enough that it will bug me every time I walk in the door and especially when I need to have a large flat area to weld something big or do an alignment on my track car where having a flat surface to start from makes it so much easier etc...

I have been trying to find a local contractor that has experience with self-leveling polymer-modified overlays, but have come up empty so far. How do these toppings hold up in a shop-type environment? I have a few large items on casters that I plan to wheel around the shop - like car tubs on dollies and a Celette bench which is big and very heavy. Am I asking for trouble down the road by considering using an overlay? Here's one produce I've found, MG-Krete: http://www.imcotechnologies.com/us/floorresurfacing.html

I was originally thinking that I'd leave the floor as bare concrete, maybe with some type of sealer applied. If an overlay is appropriate and recommended, I'd consider a high quality epoxy coating the floor so the finish is uniform and cleaner looking. Might this also help seal the edges of the topping slab?

I think I'll stop my ramblings here for now...

Thanks,
Tom

 

[pauls340]

Tom, i'm heading out the door in 2 minutes, but i've put down 1000's of sq ft of Mg-Krete and I will respond later when I get back. MGK and their Self Leveler will be a permanent repair. Try this website, www.spggogreen.com

 

[pauls340]

TD, I looked at the two links you put in your OP. I have ground and polished MGKrete for countertops, but never a garage floor. If you have any cracks ALL skimcoat products will at some time radiate up that crack again. Even Mg-Krete which will get to over 11,000psi. You can color MGK any color you want, just use powder color compounds. If you use MGK self leveling (called Lock the Top SLU) it's designed for an underlayment, gets to only ~9000psi and is light beige in color. I have not tried coloring LTT but some have with very good success. Lock the Top will self level at 1/4" and all the prep is clean and dry. Since you had it ground, that's it. We prespray the area first with the Activator Juice to absorb left over concrete dust. Helps the bond. The website will tell you who your MGK rep is.

 

[pauls340]

Here's a skim coat @ 1/8", a bull nose repair and a company logo with Mg-Krete

 

[TDabney]

Hi Paul,
Thanks for the info on Mg-Krete - seems like some interesting stuff. I couldn't find a link on the website where it listed local distributors?

How does this stuff perform when applied really thin? Can I use it to fill low spots where it may be 1/8"++ thick in the middle of a dip and then taper to 0"? Or is it best to apply it over the whole surface at some minimum thickness and let the dips be deeper? Do you trowel the edges smooth or is it really thin enough that it'll flow smoothly at the edges?

The working time with the material is short - 15 min. Yikes! you gotta be on it!

If used as a patch/low spot filler, it looks like it must be roughed up before top coating it with an epoxy coating to hide the color variation between the old concrete and the Mg-Krete? And is it destined to crack and spall where it's thin?

Again, it looks like a really interesting material. Sorry for the questions - just trying to learn... Is applying this in a garage/shop a good use for this product?

Tom

 

[TDabney]

Tried to attach some photos earlier but wasn't successful as they needed to be resized...

Some before and after grinding photos. The concrete is still damp in a few spots which accounts for a few of the remaining darker areas... but there is still some staining that remains.

Also attached is a PDF of some spot elevations of the floor taken using a laser level - not super accurate, but not horrible either...

Tom

 

[pauls340]

Mg-Krete will do everything you need done and then some. If you use MGK Fine you can taper it to zero. I repair trip hazards and then skim paper thin the rest of the slab so it looks like the slab was replaced. There is also no max depth. I've done 17" single lift pours at Metro Airport. You must put all control and expansion joint cuts back. Any major cracks will come back once the slab moves. All your spalled areas can be repaired. As the temp goes up the quicker you have to work, but there is a retarder to slow down the chemical reaction betw the Juice and the MGK. NO water except to clean your tools. I have a 3man crew that can do a 24x24' garage floor in 2.5hrs. Prep is clean and dry and you can not delaminate MGK. The imcotechnologies.com website shows your rep.

 

[pauls340]

Also, MGK is non-slippery no matter how smooth a steel trowel can make it. As far as painting it or epoxying it, just wait about 24 hrs for it to offgas. You might get a little ammonia smell but it will fade. The self level product, Lock the Top has to be feathered at the edge if you want it that way. It self-levels at about 1/4". As fast as you can mix in a 5gallon pail just keep pouring.

 

[cbracer]

Mg-Krete is a great top but for my floor the amount of unlevelness would require over $2000 worth of Mg-Krete material. So I decided to pour a new floor. The Mg-Krete might be strong in compression but tension isn't quite at high. And thin layers won't be enough to prevent cracks from growing if you have any cracks. If you don't have cracks in the concrete then Mg-Krete is great but it has to be troweled on. If they have a self leveler then great, but some garage floors have a 1" per 10' grade built in which can not be self leveled out.

 

[TDabney]

The self level product, Lock the Top has to be feathered at the edge if you want it that way. It self-levels at about 1/4". As fast as you can mix in a 5gallon pail just keep pouring.

If they have a self leveler then great, but some garage floors have a 1" per 10' grade built in which can not be self leveled out.

I found a video at imcotechnologies.com about Mg-Krete which was very informative. Seems like, as Paul mentions, it needs to be troweled on vs being a super runny self leveling type material. Is it really possible to hand trowel an 1,100 sq.ft. area flat?

I will do some more research into Lock the Top... My floor is generally free of cracks, and does have some slope to it. I'm not necessarily looking to have a LEVEL floor, just a FLAT(er) floor...

Thanks again for the info,
Tom

 

[pauls340]

I've only been in this concrete repair industry for eight years and i've used dozens of products trying to find the ONE product that can repair a crack in concrete and keep it from coming back...NONE, NOT ONE in this universe works. If you learn one thing on this website, concrete will crack and therefore Mother Nature always wins. I have been saying for 8 years, as soon as your repair gets to over 1/8" thick, it's only as good as the troweler.