Filling grooves in concrete before epoxy?

[kw757]

Great site. Exhausted my searching ability without avail. I want to put an epoxy flooring in my garage. The concrete is 9 years old now, so it should be fully settled. The existing grooves put in the concrete as crack preventers presently drive me nuts. They're nothing but dirt traps. They are 3/4" deep and 3/8" wide. They're just too deep/narrow, that they don't sweep out very well.

Before I epoxy, I was thinking of filling the cracks with Stone Mason brand Concrete Crack Filler (which comes in caulking-gun-type tubes.) I wouldn't fill the cracks to flush, but rather use my finger or a rounded tool so that they're about 1/8" deep. When this stuff hardens, it has a rough feel, and is slightly-pliable feel like tire rubber.

Then, if I epoxy over it, the grooves should be shallow and uniform, and sweep out very easily. My question is, would this be a good idea, or will it present problems with the epoxy. Since the filler would be still 1/8" lower than the floor, the only traffic that the epoxy over the filler should, in theory, see would be the bristles of a broom.

Any thoughts?

 

[premierguy]

“Sustainable’ questions are most definitely my favorite….

Feel free to PM for your mission Agent “kw757”.

 

[Andy S]

What kind of joint filler is it? Is it a 2 component or one? If it is still flexible after it dries, thats def a plus, because you dont want the joints to be filled with something that is rock hard. You might want to sand it when it is dry, to get a profile for the epoxy to bond.

 

[Timm129]

I am doing the same thing with my slab right now.
I'm using a SL-1 product (stays flexible) to fill the cracks. Then I am using Rustoelum 2 part epoxy crack filler to smooth out over the top. If the cracks are real deep I feel the crack with sand before putting the SL-1 over the top.

 

[Kevin54]

Let me ask this, and I imagine some people has done it. The cracks run down thru the saw marks. The slab has cracked and settled where it is going to go for a few years now. Has anyone ever tried to fill the cracks with Bondo and then sand down flush? Would it not hold epoxy if it had a primer over it first. It wouldn't be much different than primer and paint on a car body. I'm not talking the box store Auto places brand name bondo, but a filler along those lines none the less.On a car, you have extreme heat differentials and probably much more so than a concrete slab. The saw cut would be rough to give it bite, and the primer, then epoxy would seal it. The only downside I could see would be moisture from underneath, but if no moisture is present, then it should not affect it. If any moisture was present to affect it then it would also affect the epoxy flooring topcoat. Correct? Or am I missing something?

 

[WolverineCoatings]

There is more to consider here than meets the eye. First, there are MANY products out there to fill and expansion joint or stress groove. The first thing to remember is that you should always use a product that is compatible with the product you are going to topcoat with. There are many one component materials that work pretty well unless they become sealed. Then, they don't have a strong enough bond to hold once the hydrostatic pressure is sealed in. They become the point of least resistance for that pressure to escape. Another consideration is that the material is flexible and will remain flexible over time. Some products use plasticizers that leech out over time and then become brittle. You've probably seen window putties and caulks that get hard, brittle, and even shrink over time. Same principle...

So,

1. Use a product that is compatible with the topcoat you intent to use. Contact that manufacturer and ask...
2. Once you complete #1 you probably won't even run into #2... But, just in case... Don't skimp... A cheap joint filler can cost ya' big time later!

Good luck with your project!

 

[thegarageguy]

Bondo will fail big time. Especially if there is movement. Cant recommend any products but the cracks should be chased opened with a v-groove crack chased, cleaned and possibly stiched. Then a flexible patching material should be used.

 

[Blazz]

I am in the process of DIY epoxy coating my garage floor as well. I was told by guys at epoxy-coat.com that liquid nails would work good for filling saw cuts and gouges in concrete before epoxy application.

 

[Aberdale]

I would consider epoxy coating the floor first, then use an elastomeric (flexible) crack filler afterwards. A flexible filler will expand and contract as the temperatures rise and fall. If you use something more rigid (like bondo) it will crack and spall.

In my shop, I did not epoxy the floor, but the cracks did become a nuisance for collecting dirt and chips. I used construction adhesive as a crack filler and it worked great. It stuck to both slabs, and actually expanded a little as it cured, leaving a hump. I simply cut the hump down flush with a razor blade after it cured, and it has held up a couple years now and still looks like the day it was installed. Being flexible, I don't think it would be compatible under an epoxy coating.

Dale

 

[AlphaGarage]

There are epoxy products that do retain a level of flexibility after they're fully cured, and they can be coated over with other epoxies, but as mentioned you need to make sure that the filler and any subsequent over coat are compatible.

Cracks or expansion joints can look unsightly and they trap dirt and spills making it difficult to maintain the floor and keep it looking sharp and clean. If the cracks are large enough they also make it difficult to move carts, tool chests, jack stands and other items. A good crack filler will take care of those issues.

For a small crack it’s fine to just fill it with the filler, however with larger concrete cracks or joints you should take the time to first form a “v-notch” in the crack – this is known as “chasing the crack.” Here’s why chasing the crack is important…

After a crack or expansion cut is filled with putty, as the concrete expands or shifts it can compress the putty and squeeze it up and out of the crack. If too much putty is forced up - it may cause the epoxy coating to split on the surface.

One way to help prevent this is to cut or grind a “v-notch” along the crack’s length before the putty filler is applied. The notch will spread out the pressure and help minimize the chance of the epoxy coating splitting.


In the top example we have a crack with our filler IntegraFlex 1921 (green) but no v-notch.

The bottom example shows that a V-notch is cut first, and then IntegraFlex 1921 is applied, followed by the other coatings. As the slabs shift the force on the IntegraFlex 1921 is spread out, minimizing pressure on coatings. A flexible filler also helps if the slabs separate, moving apart from each other.

There are several tools available to chase the crack. Probably the most common DIY method is to use a hand held angle grinder. There are blades made specifically for cutting the v notch, but they can be hard to find. A wide grinding blade or diamond cup wheel at an angle will also do the job, check with your local tool shop for recommendations.

Note that the larger the crack, and the more putty used, the greater the potential displacement and problems. So if the floor has a deep “never ending crack” rather than completely filling it with putty you should first stuff some “backer rod” (available in hardware stores) in the crack and then apply the IntegraFlex 1921 putty. The backer rod should be about 1.25x larger than the crack, it will compress when it’s inserted.

IntegraFlex 1921 is a 100% solids, two-component polymer hybrid resilient filler for expansion joints and cracks in concrete or masonry. When cured IntegraFlex 1921 is extremely durable yet retains excellent flexibility (up to 50% elongation at 70˚f), it is self priming, and provides exceptional adhesion characteristics. IntegraFlex 1921 is recommended for expansion joints in general industry as well as expansion joints of garages, highways, bridges, driveways, sidewalks, and marine decks. For vertical or overhead joints and cracks we offer IntegraFlex 1922. Both IntegraFlex 1921 & 1922 provide an excellent bonding surface for other Wolverine Coatings Corporation products like BondTite 1101. A one gallon kit will fill approximately 165 cubic inches.

 

[LegacyIndustrial]

Do not use a "caulk" it could become a "bond breaker".
Epoxy likes to sit over Epoxy joint materials.

 

[slothfryk]

I'm reviving this thread. It was going in a terrific direction, but I feel like it stopped just short of a true conclusion.

When discussing the filling of control lines with my epoxy contractor, he suggests against it, but would do it without warranty. When inquiring further, I found out that the material he uses to fill is something he describes as "Quickrete on steroids." That sounds strong, but not flexible. When researching here and elsewhere, consensus is that the pads will continue to shift a little, and you need to account for that.

Looking for an elastomeric epoxy product, I came upone the PC Xtreme 96000 Polyurea elastomeric joint filler on Amazon. All the numbers seem to check out, from hardness to flexibility, to curing times. Once I got it in, though, it is really rubbery. Not to mention that in my quick back-of-the-napkin calculations projected that I would only need two 20 oz. tubes for the garage, but in reality those two tubes only filled two 10' lines. [this is why i am a disgrace to engineers and didn't pursue that career path] At $50 per 10' line, the filling of control joints would cost me over $350 in materials alone. Hard pass.

I did some more legwork. In the post above, Scotty from Legacy Industrial links to some of their products. Their name had come up in my original research, but in all honesty, was going to be more work that squirting a caulk-type tube thing. As with many aspects of life, if you want it done right, you've got to put in the time and effort. I decided to go with their product, but I'm glad I called before placing the order. I needed to confirm shipping times, because my contractor arrives a week from yesterday, and slow shipping could ruin my project. This contractor is under such high demand that I have to schedule him over a month out.

Paul over at Legacy Industrial gave me some honest consultation that I really appreciated. I had targeted the Gel Crack Filler because it was similar to the two-part elastomeric that I was originally using. He advised that to meet my goals of filling the scraped-in wide grooves of a modern garage floor, rather than the cut-in lines of an industrial floor, that the Xtreme Set 100 Crack/Joint Filler was the way to go. Not only is it available in-State for quick shipping, but it does a better job filling the wider grooves I'm working with.

Paul also recommended that I follow all the steps in their Video so that I got the best results. TBH, I was a little skeptical at first about the sand in the grooves first. But as I thought back to a materials class I took, it makes sense. The sand/epoxy mixture become a matrix material, not much different from the way tire rubber is constructed to flex based on the ratio of carbon-black to rubber or the way that carbon fiber is designed not to fail catastrophically. The epoxy matrix can allow for shift through the millions of contact points with each grain of silica sand. The result is decreasing the likelihood that a single solid crack will form. Instead, hundreds or thousands of small deformations will occur without actual failure.

I am excited to see how this material holds up over time. I think that I'll leave the two lines (20') I've already done in the PC Xtreme, and do the remainder (40') in Xtreme Set 100 sand-mix. Then I'll make mental notes of how they hold up and fix the first one to fail with the other. This thread will be my reminder of my work.

Has anyone else used these or similar products in their projects?

 

[LegacyIndustrial]

Nice analysis. If it helps our Orlando install company uses the Xtreme Set 100 product everyday on garage floors, industrial floors, kennel floors, etc... Works like a charm and they would cry if I took it away. lol.

 

[Shea]

Xtreme Set 100 is awesome stuff! We did an article on it where we created deep grooves, spalling, and crack chasing lines in some concrete pavers. It took all of 20 minutes or so to fill the grooves, holes, and crack lines then grind them smooth.

You can read about our results here:

http://allgaragefloors.com/fast-easy-concrete-crack-repairs/

 

[Ch3No2]

I used Ardex Feather Finish with Excellent results. I put down Red Plaster Tape on both sides and putty knifed it in the Expansion Joint, peeled up the tape and hit it with a 50 grit sanding disc...ready for Epoxy. It has held up very well and that was 11 years ago.

 

[slothfryk]

Scotty- definitely don't take it away! Sounds like you've got a real winner.

Shea- love your site, man. Did some of my original legwork there. Totally drool-worthy projects in your gallery. I really wish I could have talked wifey into a bigger garage, but I'm patient. This won't be my last project.... However, I had missed your Xtreme Set 100 write up, so I appreciate you sharing it. Great info!

Ch3No2- killer build thread! Where are you in SoCal that it snows? Am I safe to assume you've got some elevation? I just looked into Ardex Feather Finish, and page 4 of their technical data sheet advises against using it in expansion and control joints. I'm glad that it's working for you, and wish you continued good luck. From the looks of your build thread, you had a good hand in ensuring quality craftsmanship in your construction. I, sadly, have no such history with my place and can only assume it was built by a similar team of unconcerned individuals as my last place. (same builder, ironically)

 

[Ch3No2]

Ch3No2- killer build thread! Where are you in SoCal that it snows? Am I safe to assume you've got some elevation? I just looked into Ardex Feather Finish, and page 4 of their technical data sheet advises against using it in expansion and control joints. I'm glad that it's working for you, and wish you continued good luck. From the looks of your build thread, you had a good hand in ensuring quality craftsmanship in your construction. I, sadly, have no such history with my place and can only assume it was built by a similar team of unconcerned individuals as my last place. (same builder, ironically)

slothfryk.....yes I am at 3675' in a town named Acton...off the 14 frwy up a hill between Santa Clarita and Palmdale. I had the best hand I know involved since I develop and build commercial buildings for a living...that's why the build took so dam long...lol.
Thanks