My garage slabbed was poured last week there is an issue. There was delay of a couple of hours in the middle of pouring. When the next truck showed up they continued to pour and finished the last part by hand. There is a bump in the cold joint and a difference in texture between the 2 sections. This cold joint runs the entire width of the slab. My contractor is coming tomorrow to look at the problem. What can I expect him to do at this point?
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Problem with new garage slab
- Thread starter penny79
- Start date
spotco2
Well-known member
How large is the slab? What part of the world are you in?
Is there rebar, wire mesh or fiber in the concrete?
If you lay a really straight 10' board over the bump, how bad is it?
What is the subgrade under the concrete? Was is properly compacted before the pour?
How thick is the slab?
A saw cut along the bump area would control where the concrete is going to crack when it does.
Is there rebar, wire mesh or fiber in the concrete?
If you lay a really straight 10' board over the bump, how bad is it?
What is the subgrade under the concrete? Was is properly compacted before the pour?
How thick is the slab?
A saw cut along the bump area would control where the concrete is going to crack when it does.
dcs Inc
Well-known member
A cold joint WILL crack for sure.
How large is the slab? 28x22 What part of the world are you in? I'm in Northern Illinois
Is there rebar, wire mesh or fiber in the concrete? wire mesh
If you lay a really straight 10' board over the bump, how bad is it? It is bad
What is the subgrade under the concrete? Was is properly compacted before the pour? gravel and yes it was compacted
How thick is the slab? 4 inches
A saw cut along the bump area would control where the concrete is going to crack when it does.
Is there rebar, wire mesh or fiber in the concrete? wire mesh
If you lay a really straight 10' board over the bump, how bad is it? It is bad
What is the subgrade under the concrete? Was is properly compacted before the pour? gravel and yes it was compacted
How thick is the slab? 4 inches
A saw cut along the bump area would control where the concrete is going to crack when it does.
A cold joint WILL crack for sure.
I'm wondering what I can expect my contractor to do at this point. Does it need to be pulled out and restarted?
A cold joint WILL crack for sure.
I'm not sure that's an absolute. I think it would be more reasonable to consider this particular situation on it's own merits. Two hours between trucks is unreasonable, but that in itself doesn't guarantee a "cold joint". Much depends on the mix, it's set time, whether or not it contained water reducer or set retarder-- all things to consider. I good finisher can minimize the risk of a cold joint by periodically breaking up the edge of the concrete to prevent set while waiting for the truck. A proper "rough" edge left on the concrete can provide additional "mechanical" bonding if the bond from hydration is impaired. Reading the details in penny79's subsequent post, it sounds as though the subgrade was properly impaired and there is reinforcing mesh in the slab; all good reason not to remove it. If the finish is deficient, ask the contractor to remedy that. He may agree and seek recourse from the ready mix producer for the poor delivery service. Also, consider control joint saw cuts that would incorporate the cold joint into the cut. As a last resort, taking a couple of 4" core samples through the cold joint will confirm the concrete's integrity.
Bob
I'm not sure that's an absolute. I think it would be more reasonable to consider this particular situation on it's own merits. Two hours between trucks is unreasonable, but that in itself doesn't guarantee a "cold joint". Much depends on the mix, it's set time, whether or not it contained water reducer or set retarder-- all things to consider. I good finisher can minimize the risk of a cold joint by periodically breaking up the edge of the concrete to prevent set while waiting for the truck. A proper "rough" edge left on the concrete can provide additional "mechanical" bonding if the bond from hydration is impaired. Reading the details in penny79's subsequent post, it sounds as though the subgrade was properly impaired and there is reinforcing mesh in the slab; all good reason not to remove it. If the finish is deficient, ask the contractor to remedy that. He may agree and seek recourse from the ready mix producer for the poor delivery service. Also, consider control joint saw cuts that would incorporate the cold joint into the cut. As a last resort, taking a couple of 4" core samples through the cold joint will confirm the concrete's integrity.
Bob
From what I can tell nothing was done in that 2 hour period to help insure the strongest bond. The 3rd truck had mechanical problems and sat waiting for a higher up to evaluate it. After that another truck was ordered and that was why there was a delay. The initial pour was finished by machine but the remaining portion was finished by hand. I know this can account for the difference in color and texture. Also on the side of the slab are "curbs" and one them is already showing a crack and a hole where the concrete is not smooth.
dcs Inc
Well-known member
Hey man, It gonna crack. Hairline at the best. Yes, you can chop it back and attempt to mix it up but there is a weak bond created and it will crack. Now keep the temps constant and you have half a chance of it not showing up on the surface. What can you do? You can use a crack chase blade to open it and fill with an appropriate crack fill epoxy. Saw cut a new control joint very near and that should recontrol it.
Normally they cut back the concrete and install a form. Pull the form when the next load finally arrives. This will produce a straight fracture line. Saw cut it open when finished.
Normally they cut back the concrete and install a form. Pull the form when the next load finally arrives. This will produce a straight fracture line. Saw cut it open when finished.