Garage Floor

[Paul J.]

Re: Garage Floor

Paul, I guess you are the expert and the rest of us should shut the FU. Your right I missed the last word in the first paragraph of post #5. How dare I.

Since you are the expert why didn't you explain the rest of the causes of spalling, the ones that are applicabile to the OP, like putting plastic under the concrete which he intend to do, like sealing the concrete too early, the wrong kind of aggregate, pressure washing, etc. or maybe explain to the OP that he wants to avoid pouring concrete in the winter to avoid the adding of calcium cloride (salt) if he is in a northern state. No instead you remove my tonsils with a spool and attempt to intimidate others from posting on a concrete subject. I'm done.

Don't get upset Robert, no offense was meant. I only responded to your post because what you said is incorrect and I did not want anyone to get confused. Putting plastic under the concrete and sealing it too early will actually strengthen the slab, as it keeps the moisture in the pour longer and allows the maximum amount of hydration. We actually sprayed a sealer on freshly poured bridge decks in the summer months for this very purpose, and it was also stated in our regulations. I thought that I touched on the aggregate because it is specified in the mix. A reputable plant will not cheat on this. I also don't understand how pressure washing has anything to do with spalling. While it is advisable to stay away from salt, it usually only causes spalling if the W/C ratio was weakened at the top of the slab, or if there is unprotected steel in the slab, or if the concrete was a very low strength mix. Chloride accelerators are still used in certain mixes and have been tested as safe when mixed properly. If the OP wants to pour during the winter, the key is to keep the water in the slab from freezing, and there are several ways to do this.

Paul

[Dick W.]

Re: Garage Floor

I thought that I touched on the aggregate because it is specified in the mix. A reputable plant will not cheat on this. I also don't understand how pressure washing has anything to do with spalling. While it is advisable to stay away from salt, it usually only causes spalling if the W/C ratio was weakened at the top of the slab, or if there is unprotected steel in the slab, or if the concrete was a very low strength mix.
Paul

I always pour 5,000# mix for my driveways and garage floors, cost is a little higher, but the results are worth the difference. The last driveway I poured we used air-entrained 5,000# mix. Expect that to outlast me.

[Gerard F.]

Re: Garage Floor

Don,

If the garage is going to be heated, a vapor barrier under the slab is a must. Put the visqueen over a 2" layer of pea gravel, or other open graded material, to prevent moisture from traveling upwards. Moisture from the subgrade moves to the warmer temperatures upward.

Also have your contractor consider some reinforcing in the slab, maybe #4 at 12" BW for a 6" slab, or #3 @12" BW for a 4" slab.

I know you were only interested in the finish (SB light broom finish on my score sheet), but I'm just an engineer.

[Gerard F.]

Re: Garage Floor

Sorry Don,

I missed the post where it was already poured. But I see the extra rebar in the picture.

[Don H.]

Re: Garage Floor

Thanks Jerry & all that replied. We did plastic, then 2 inch "blue board", rebar, then heat tubes (see picture). I am finally headed home to see it in person. Darn that stupid thing called work. Thanks again, Don H.

heat before pour.jpg

[Gerard F.]

Re: Garage Floor

That looks great

Passes my inspection.

[Paul J.]

Re: Garage Floor

I always pour 5,000# mix for my driveways and garage floors, cost is a little higher, but the results are worth the difference. The last driveway I poured we used air-entrained 5,000# mix. Expect that to outlast me.

You got that right! You won't have to worry about spalling either. Residential codes vary but most require at least a 2500 psi mix. Roadway rules require around 3500 psi and above, although 3000 psi is sufficient. The better roads that you travel on can have up to 5000 psi. I believe that we used 4000 psi on the bridges but don't quote me on that. With mixes over 3500 psi you seldom see spalling, because of thier compressive strength.

[Gary C.]

Re: Garage Floor

Don,

Looking good in the photos. I've let concrete cure for a minimum of 7 days on the two shops I've built before doing any construction.

Am sure there are lots of varying opinions on how long to wait before driving on freshly poured concrete.

Keep the photos coming.

Gary
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