Pouring concrete Need Advice!!!

[Petro55]

Hello,

Last week I got my concrete garage floor saw cut around the edges and removed. My garage floor was heaved and had some major cracking. I have a monolithic pour so the edges were saw cut and I am left with about 1 inch of left over to the bottom of the wall stud.

I have a couple questions for the concrete experts(I thought that is who I hired but I am beginning to really question them).

1 I live in Chicago the garage is non heated, what should I have them do around the edge of the concrete? Drill holes insert rebar? Expansion board?

2 Should they use rebar or mesh in the concrete?

3 What kind of expansion joint should they do? Saw cut? How deep?

4 Can they pour the concrete over the existing 1 inch left over slab right to the wood 2x4?

I also bought a 6 mil vapor barrier I was going to double up on to put over the base. I was going to have them dig out and compact 6 inches of base, the old floor was poured right over the dirt…

If you have any other pointers or advice to make this a perfect pour let me know.

Mike

 

[ConCretin]

Petro55, If I understand correctly, you have a monolithic slab where the walls bear on a thickened edge. It sounds like you have removed the slab in the middle and left the thickened edge. If I've got it right, here's how I'd respond to your questions;

1 I live in Chicago the garage is non heated, what should I have them do around the edge of the concrete? Drill holes insert rebar? Expansion board?

I would definitely drill and epoxy dowels into the remaining slab. #4's at 12" centers will help tie everything together.

2 Should they use rebar or mesh in the concrete?

You want some form of reinforcing. Mesh is OK but rebar is easier to support and is more likely to remain in the center of the slab rather than end up lying on the subgrade. I'd probably just stick with the #4's at 12" OC

3 What kind of expansion joint should they do? Saw cut? How deep?

I think what you are referring to is a contraction joint and you definitely want them especially since you are tying into an existing slab that will restrain the new concrete and cause cracking.

If the existing slab has CJ's, line the new ones up with them. Otherwise break the slab into approximate squares of 10 -15 feet ( I can't remember your slab dimensions). Cut should be done with an early entry saw immediately after finishing. Cut 1/4 of the slab thickness.

4 Can they pour the concrete over the existing 1 inch left over slab right to the wood 2x4?

Sorry, not sure I understand the question

I also bought a 6 mil vapor barrier I was going to double up on to put over the base. I was going to have them dig out and compact 6 inches of base, the old floor was poured right over the dirt…

I like the idea of installing a good base material and using a vapor barrier.

If you have any other pointers or advice to make this a perfect pour let me know.

Most important is to keep the amount of water in the concrete as low as possible, which means pouring a stiff mix or asking for a mid range water reducer

Also be sure to cure the concrete properly by maintaining it in a continuously moist condition for at least seven days.

I hope this helps anf good luck with your placement.

 

[Petro55]

Thank you for your reply, let me elaborate on question 4. The slab was cut one inch from the 2x4 on the base of the framing for the wall.

I wanted to raise the level of the floor to cover that exposed one inch of existing concrete so it looks like a single slab. Is that a bad idea? Will the concrete crack on the edge along the walls?

Petro55

 

[ConCretin]

The 1" thick section is likely to crack Petro55. You could accomplish the same thing by grinding a 45 degree bevel on the top of the existing slab back to the face of the wall. The new concrete is less likely to crack if it's bearing on a sloped surface rather than a sharp edge. It would take a little work but a diamond grinder would take the corner off pretty quickly.

 

[OccupantRJ]

Be home when the pour is being done. Most lamenting on bad pours I have ever read about was when the owner was not present during the pour. Once the concrete sets up is not the time to see how things went.

 

[skulldrinker]

get a permit at least some inspector will have to ok it.

 

[Petro55]

LLWILLYSFAN- Thanks for guidance, I will grind those suckers down. I have a angle grinder, where can I pick up a diamond wheel for it?

Skulldrinker- I am in the process of getting a permit right now, what will the inspectors be looking for? Structural integrity or basic concrete stuff ie correct pitch, sub base etc

 

[06Z06]

Im thinking about doing this same project. Interesting read, let me know how it turns out.

Jeff C

 

[dcs Inc]

LLWILLYSFAN and Petro55.

Guys here my take. Petro, you stated the slab had heaved. Does it look as if the center of the slab raised? If so, I'd suggest attempting to have the new slab be independent of the old footing system. Often monolithic pours will have a very heavy edge that was poured above the frost line. A heavy freeze and a little help with moisture in the soil will heave a mountain. The differences in slab thicknesses will cause the heavy (thicker) concrete to sink more and the lighter (slab) to raise. If that's not the case well..... never mind

 

[spotco2]

LLWILLYSFAN- Thanks for guidance, I will grind those suckers down. I have a angle grinder, where can I pick up a diamond wheel for it?

Home Depot has one made by Rigid that fits a 4-1/2" angle grinder for $39.