Concrete Floor Seam closure Caulk

[Bernie Kopfer]

My indoor concrete floor has saw cut seams on a 6ft grid. They are 1/8 to 3/16 wide and 1/2 deep. Great dirt catchers. I can get them really clean and the concrete is less than a year old. I would like to fill them with caulk so that they are level and not debri catchers. II know there are products made for this but they are off shade gray so I would like to use a clear filling and let time and wear blend it in. The floor might be sealed but it will not be painted.
What material has worked well for others? Silicone or poly urethane or...? Expoxy is too expensive. Thanks

[Frank Pratt]

If it is a good stable slab, sanded tile grout works. I did it in the my shop at work about 10 years ago & there has been no shrinkage or cracking

[Bill Dufour]

Self leveling concrete sealer caulk in a tube. I suppose you could squirt it into a bucket and tint it to match.
Bil lD.

[Charlie Velasquez]

They make tubes of rubberized tile grout in almost any color. Check your local borg or tile store.

[Frank Pratt]

They make tubes of rubberized tile grout in almost any color. Check your local borg or tile store.

I did not even know that. Thanks.

[Chuck Saunders]

When caulking these cracks you want to only bond to two surfaces. Stuffing the crack with backer rod will support the caulk and allow it to only bond to the two opposing edges. Any movement (not expected but that's why they cut them) will not pull the caulk away due to being bonded to a side and the bottom better than the other side.
Chuck

[Martin Siebert]

I have probably tried every conceivable way to do this and while I have had pretty fairly decent results.....there is just no perfect way, or at least I haven't found it yet. Whatever you use or do it will always work better if the slab is stable and fully cured. Self leveling stuff, like they use around outdoor swimming pools works. but the color match might be a problem. Honestly, I would suggest you forget about the color match because you probably wont get it dead on anyway and you are kind of "throwing the baby out with the bath water" worrying about something that has nothing to do with patching and keeping cracks filled. Another way to look at it is; if the color/aesthetic's means that much then paint the whole floor.
I have had very good results {not perfect} with either Rockite or thin set type mastic like you use for ceramic tiles. There is also a product called "Non-shrink/Non-stain" grout that works excellent, but you will probably have to order it. When using any masonry product it is best if you pour a little brick cleaner {muriatic acid} into the crack. It's dangerous stuff to use, the fumes will burn your throat and eyes so wear protective gear. The problem is that the other stuff {filler} don't work too well without it.
As Mr. Saunders posted above, you want backing of some kind. I find that clean white "playsand" works real good. You may get some spots where it takes quite a bit to fill it. Best of luck, you are gonna need it fixing cracks. Filling them is not the issue, it's getting it to stay.

[Bernie Kopfer]

Apparently there is no method to assure perfect results. This concrete floor was poured over an existing wood floor and has already in a years time shown that shifting is occurring. Fortunately it will work, sometimes we have to take what we can get. So I will plan on movement as time goes on. A filler that stays flexible and bonded would be nice. Perhaps self leveling concrete filler will be best. Someone recommended a butyl rubber caulk such that is used for gutter repair. Any thoughts? This floor will see minimal water if any. Bonding with ability to stretch and compress is going to be crucial. And apparently experience says that a flexible backer rod or even sand will make a difference?

[Walter Mooney]

Bernie,

Chuck’s reply is 100% dead on — the caulk will only ‘work’ properly if if it only adheres to two surfaces. So put backer rod in first and then caulk it. But if you’re going to ultimately paint the floor, use a urethane caulk and not silicone, because paint won’t stick to silicone caulk. You can probably buy the urethane caulk at the same place you buy the backer rod.

[Jason Roehl]

Ditto on the backer rod recommendation. The cross-section of a properly-caulked butt joint should look like an hour glass—the center of the joint should be the thinnest of the cross-section so that it flexes there, while the bonding surfaces are much larger.

[Bill Dufour]

Or go the other way and use a contrasting grout color. You will not be able to get and exact color and sheen match so why try? Since this is over an existing wood floor you will always have issues with movement. Will the wood rot away over time?
Bil lD.