Any concrete tradesman here?

[ochster]

I have some cloudy, dark blotches, around about 1/3 of the perimeter of my shop. It has hydronic floor heat and is kept near 70deg., but these don't appear to be going away. I wan't to put a catylized expoxy coating on, but am waiting to make sure adhesion will be good. It is a 5"monolithic slab with 10hx16w incorporated footings, 6mil plastic underlay, poured two months ago. Any insight or sugestions?

 

[Keith M]

ochster; In normal conditions it takes 30 days for concrete to cure, before you can put epoxy on you have to ether shot blast the floor or grind it to take the latents off the top of the concrete, Polyester floors are good for shops too You can put on three coats of polyester and two color coats with sand in every layer but the last color coat, then you will have non skid and washable surface, good luck, Keith

 

[ochster]

These blotches I call "clouds" are dark grey in color, and are smooth as glass. They look and feel as if varnish or shelac were spilled. You can scrape a similar finish type crust off the top, only to still have it underneath. They only exist a couple inches in from the sill plate, wich was at one time very wet. I also wonder if this is a "overworked" condition, and nothing to worry about?

 

[Jonala]

Ochster,

I poured a new slab myself last August. The last area to cure is where we put the "wettest" concrete. It has a dark cloud. I'm not worried about.
I not a concrete expert, just a weekend "Toolman".

 

[ochster]

My concerns were around the sealer lifting, or not adhearing because of these. I sure would not wan't to strip that stuff off!

 

[Patman]

Are you sure the floor tubing is not leaking in that area keeping the concrete a little damp? :ugg:

 

[bbbom]

Assuming that Patman's scenario is not the problem (hopefully), the sealant that you plan on using should have pretty specific application instructions that include how much cure time is required for proper adhesion at given temps and humidity.

Do the clouded areas seem cool or damp to the touch compared to the rest of the floor?

 

[ochster]

Patman, That would be my worst nightmare! Thankfully I'm sure it isn't though, my tubing is actually 16in. from the perimeter wall.

bbbom, they were dry after further inspection, I had a concrete finisher look at it, he believes it had to do with the excelarator and or lot's of water. It was poured over 6 mil plastic, and actually pushed water up around the edges. He reccomended I sand the whole floor with a 17in. stripper with 20 grit. I can't believe what a work out that was, I have never had arm pump so bad! Of course at 135lbs., the darn machine almost outweighed me. The sanding took the "crust" off the top of the imperfections, though they still exist. I washed it and am letting it dry, then will apply a Sherwin Williams product called "Armorseal 1000 HS". Thanx for the input

 

[Patman]

Whew! That would have been a REAL drag.

Let me know how that SW coating works out, I'm going to do something in the spring to my floor.

 

[whyz]

Right On!

nice warm floor.. with Pex tubing should last forever..
as far as the concrete ,,no biggie i believe its the mix.
those blotches or clouds are just more concrete/water in those certain areas
which will give ya that sheen look....Awesome.....

I really like that floor...Im a plumber and am definately looking at the inside of my house to run hydronic heat with 1" Wirsbo tubing,cause my floor gets really cold and i believe it'll distribute heat alot more even'ly than conventional heating will never come close to...... See Ya....

 

[ochster]

I fretted big time about brands and types of floor sealers/paint. I alway's wanted a painted gray floor. I had worked around them at several shops I worked at, and was aware of the problems that could arise. A industrial coating rep convinced me this product by SW, particularly in clear, was the best for what I wanted. He also told me the critical step for adhesion is the first coat, as well surface prep obviously. He told me to use a thin first coat diluted 20% with thinner, thus getting the material into the pores instead of on them. Wait till you could walk on it, and apply a 6mill topcoat. He stated the color pigments do not allow the penetration for adhesion. I'll find out, and post an update.

Whyz, I used 5/8" pex on 12" centers, split into two zones. Each zone was started from the center of the floor to maximize heat retention as it worked to the outside of the slab.

 

[HLT]

Ochster,
I've been in the Concrete bus. 20 years. Everything from truck driver to plant manager to quality control to boom pump operator. The blotchiness you see is slow curing concrete due to it's location near the footings. Since your slab was poured monolithic, the large footings will take much longer to cure completely than the relativly thin slab. (By the way, mono pour is the way to go for best overall structural integrity). These areas can actualy take years to completely cure and bleach out due to moisture in the ground that will keep the concrete cool and moist. Your only concern should be if you see any white powder forming on the top in the grey areas. This is called eflouresense and is caused by natural salts leaching up from the ground. I'd wait 30 days from the pour date and if no major cracks or other problems, go ahead and paint it. Have fun.

 

[whyz]

HLT...

What do you think of Fiber Mesh?
I have it in my garage and just wanted to know,,,,does it crack? and how much Sq. Ft. could you pour without it cracking?
There's no expansion joints at all on a 26 by 26' flr....

And what would you call a good mix for inside of my house using the same type of application as Oshster.. without it cracking??

Thank You... >>>>>You Da Man:D

 

[HLT]

whyz,
Fiber mesh was a good choice since you have no expansion joints. It won't keep the concrete from cracking but will minimize their size and appearance. The old saying is "Ice cream melts and concrete cracks". Basically, the fibers serve the same purpose as wire mesh in a slab. What to use inside your house depends on what it's for, whether you are pumping it and how hard you want to work to finish it. The best way to minimize cracking is to pour the concrete dry. But that makes it harder to work so many contractors will pour it too wet and live with the cracking and shrinkage.
By the way, since you are in Gresham, do you ever ride at Mountain View? Great track!! When my son used to race a lot, we'd go there after the Washougal Nat. It was always fun to race there as they are a great bunch of people. Have fun.

 

[bwalker]

Ochster, If it is still wet you could put some Dow flake on it to draw the moisture out.