Problems with new driveway (crack)

[shadow338]

Hello,

Seeking advise and opinion here.

In the end of Oct last year (2023) I had contractor building a new driveway with 4 inch of thickness.
Now, after only 2.5 months, I'm already seeing a huge crack from end to end in the first section of the driveway. (the sections on the new driveway were made smaller when compared to the old)

I contacted the contractor and he said this may happen for a lot of reasons and that he will try to sort out the problem (This was a week ago and I still need to hear from him again)

On the day the concrete was poured, it was not too cold or rainy. As per the contractor advise, we waiting a full week (possibly even more) before we drove our car into the driveway.
After that, only regular size cars go on the new driveway.

The soil here is brown/redish clay and it was full of roots, but those were removed the best it was possible and a layer of gravel poured and flattened in preparation for the concrete.

Since the driveway was built, I was checking it pretty much every other day just to be sure nothing wrong would appear.
I can't pinpoint exactly which day the crack started to appear but coincidence or not it was after some heavy rain in this area.

What could be causing this?


Thanks in advance!

 

[Steve123]

There is an old saying about 3 sure things about concrete:
-it's heavy
-nobody is going to steal if from you
-it's going to crack

Judging by how quickly it appeared, I would guess that is a shrinkage crack. Concrete shrinks as it cures. Shrinkage is more of a problem on excessively watery mixtures.

Face it, you are going to have to live with it. Contractor isn't going to jack-hammer and repour your driveway because you have the unique experience of having a crack in the concrete.

 

[shadow338]

If it's a shrinkage crack that could be caused by too much water in the mixture then I would think someone is at fault. (wrong/poor ratio of water)
Even the old driveway that was 38yrs old had less amount of cracks/damage in this specific section of the driveway.

Since I wrote this post, the crack clearly opened a bit and my concern is that water from rain is pouring inside this crack to the clay soil. I thought cracks had to be taken care otherwise it speeds up the damage of the concrete by allowing water inside the crack.

 

[Sparky617]

Typically they will put in a control cut to force the cracking into a straight line and largely unnoticeable. Either by striking a joint while the concrete is still plastic, or after it sets by cutting a joint in with a concrete saw. As Steve notes, concrete will crack, it is a matter of how do you make it less noticeable. Control joints are how it is done. Are there any control joints in this slab? If so, how far is this crack from the control joints? On larger slabs you also install an expansion joint with a tar-impregnated material.

 

[Steve123]

Typically they will put in a control cut to force the cracking into a straight line and largely unnoticeable. Either by striking a joint while the concrete is still plastic, or after it sets by cutting a joint in with a concrete saw. As Steve notes, concrete will crack, it is a matter of how do you make it less noticeable. Control joints are how it is done. Are there any control joints in this slab? If so, how far is this crack from the control joints? On larger slabs you also install an expansion joint with a tar-impregnated material.

In the first photo, you can see a control joint just a few feet away. Stuff happens.

In a freezing weather, water can get in the crack, freeze and expand, making the crack bigger, repeat.

You can put caulking (polyurethane or similar) on the crack, but I don't think I have ever seen a crack "repair" that was not more visible than the original crack.

 

[shadow338]

Typically they will put in a control cut to force the cracking into a straight line and largely unnoticeable. Either by striking a joint while the concrete is still plastic, or after it sets by cutting a joint in with a concrete saw. As Steve notes, concrete will crack, it is a matter of how do you make it less noticeable. Control joints are how it is done. Are there any control joints in this slab? If so, how far is this crack from the control joints? On larger slabs you also install an expansion joint with a tar-impregnated material.

There are control joints on each slab and the crack is right in the middle between the joints.
I'm wondering if this can be a depth structural failure crack that is caused by the slab flexing because it is sitting on soft or poorly prepared soil. Maybe not enough gravel, maybe they didn't compact the soil properly or enough, who knows...

 

[shadow338]

In the first photo, you can see a control joint just a few feet away. Stuff happens.

In a freezing weather, water can get in the crack, freeze and expand, making the crack bigger, repeat.

You can put caulking (polyurethane or similar) on the crack, but I don't think I have ever seen a crack "repair" that was not more visible than the original crack

I may not have an alternative than repairing the crack cose in this rain and sub-zero temperatures the crack is definitely opening more.
The issue here is, since the driveway was done just 2.5 months ago, is the contractor now off the hook completely? I mean, at least I expect him to fix this crack or I now need to hire a new contractor that does this? The crack goes deep pretty much from the surface to the bottom of the slab. The slab is definitely "broken" in two peaces at this point despite having control joints.

 

[shadow338]

Here's some more pictures just taken now. The crack seems to be open a bit since my initial post.

 

[PJB12]

Did you happen to pay by credit card? If so, the credit card company most likely will be helpful in getting a refund for at least part of the expense of the driveway.

The early cracking in your slab might have a lot to do with ground preparation. Clay under concrete can be bad in cold climates because it doesn't drain. Water goes through concrete, lays on the clay and freezes, expanding as it freezes.

At our yard, also on clay, "Contractor A" did the back yard part of the driveway and garage slab. A bit of sand was laid on the clay. Like yours, it cracked in many places very soon after curing. (About 28 days is full cure. Ours was about 60 days old.) It was a six bag mix. There are control joints at 10 foot maximum. The slab is 4" thick with mesh pulled to the center of the thickness.

"Contractor B" poured the driveway that's not in the back yard. He said pouring on clay is a bad method. His guys dug out clay for ten inches and replaced it with sharp sand, mechanically compacted. They put one inch of sand and compacted. Then repeated until all 10 inches were done. Twenty some years later, there are no cracks in that part. This is the part that gets driven upon daily. It also is 6 bag mix. The control joints are also 10 feet maximum section. The slab is 4" thick with mesh pulled to the center of the thickness. There is rebar into each side between control joints, pinning them against lifting.

Another concrete cracker is ice melt products. The ice melts and the water goes into the concrete. When the water re-freezes, it can crack the concrete. Water that did no penetrate deeply will cause spalling.

If you do end up re-pouring, perhaps the above can give you some idea of what to seek during the bid process.

Paul

 

[shadow338]

Did you happen to pay by credit card? If so, the credit card company most likely will be helpful in getting a refund for at least part of the expense of the driveway.

The early cracking in your slab might have a lot to do with ground preparation. Clay under concrete can be bad in cold climates because it doesn't drain. Water goes through concrete, lays on the clay and freezes, expanding as it freezes.

At our yard, also on clay, "Contractor A" did the back yard part of the driveway and garage slab. A bit of sand was laid on the clay. Like yours, it cracked in many places very soon after curing. (About 28 days is full cure. Ours was about 60 days old.) It was a six bag mix. There are control joints at 10 foot maximum. The slab is 4" thick with mesh pulled to the center of the thickness.

"Contractor B" poured the driveway that's not in the back yard. He said pouring on clay is a bad method. His guys dug out clay for ten inches and replaced it with sharp sand, mechanically compacted. They put one inch of sand and compacted. Then repeated until all 10 inches were done. Twenty some years later, there are no cracks in that part. This is the part that gets driven upon daily. It also is 6 bag mix. The control joints are also 10 feet maximum section. The slab is 4" thick with mesh pulled to the center of the thickness. There is rebar into each side between control joints, pinning them against lifting.

Another concrete cracker is ice melt products. The ice melts and the water goes into the concrete. When the water re-freezes, it can crack the concrete. Water that did no penetrate deeply will cause spalling.

If you do end up re-pouring, perhaps the above can give you some idea of what to seek during the bid process.

Paul

It was paid with a cheque as that is what most of the contractors accept without charging extra fees or at least that's been my experience.
As far as the prep work done pre-pouring, they put gravel (maybe a inch? not sure) and compacted and this was done the very same way on all the driveway sections. The original driveway was 8inch thick but the contractor said that's how they used to do in the 80's because concrete was cheaper back then. He also said that the residential standard here is 4inch and never mentioned that more was needed. btw, I don't use ice melt products. I'm in North Carolina. Thank you.

 

[havasu]

I've seen this happen when a control cut was not cut deep enough. Can you measure the depth of the cut?

 

[shadow338]

I've seen this happen when a control cut was not cut deep enough. Can you measure the depth of the cut?

I just checked. the control cuts are 5/8" deep. On another section/slab of the driveway, there is a crack right across the whole control joint so I guess that means it did his job in preventing the slab cracking in the middle?

 

[tomtheelder2020]

Not specifically relevant to this thread, but as general info regarding concrete work:

... The slab is 4" thick with mesh pulled to the center of the thickness.

The early part of my career was mostly writing soil engineering reports for residential construction and our work occasionally included investigating the cause of failed slabs in existing houses. Every one of those slabs had mesh sitting at the bottom of the concrete - presumably pulled to the middle of the thickness. There was lively debate as to whether: A) the workers had not bothered to pull up ("hook") the mesh because no one was looking; B) they hooked the mesh too close to where they were standing on it; or c) the mesh settled before the concrete set up. Every report I wrote for design of new construction (literally thousands of acres of housing) recommended that the mesh be supported at mid-slab height.

... His guys dug out clay for ten inches and replaced it with sharp sand, mechanically compacted. They put one inch of sand and compacted. Then repeated until all 10 inches were done ...

Kudos for good work. However, sand compacts more easily and denser using vibration. As good or better result could have been achieved faster, and therefore cheaper, using a vibrating compactor on just 2 lifts (3 to be really conservative). This is especially important to understand for sand in utility trenches. For trenches, the worst way to compact sand is jetting.

 

[lucyonfire]

There is an old saying about 3 sure things about concrete:
-it's heavy
-nobody is going to steal if from you
-it's going to crack

Judging by how quickly it appeared, I would guess that is a shrinkage crack. Concrete shrinks as it cures. Shrinkage is more of a problem on excessively watery mixtures.

Face it, you are going to have to live with it. Contractor isn't going to jack-hammer and repour your driveway because you have the unique experience of having a crack in the concrete.

Yes you are right

 

[Steve123]

Maybe there are other standards for driveway or concrete work, but in Ontario, we have a mandatory warranty program for new homes. The Ontario government formed a company Tarion to administer it. It may be helpful to compare what is and is not considered acceptable.

The Tarion standard for driveways is that cracks, including shrinkage cracks are acceptable if not caused by defects in material or workmanship. (It does not sound like they accept "there is a crack, therefore there must be a defect in material or workmanship" )

They go into more detail on basement slabs. In a basement slab, cracks are acceptable if less than 4mm wide. If more than 4mm wide, the builder needs to repair it, but the repair does not need to be the same color or texture (because they know it won't be).

Building Standards

 

[PJB12]

There was lively debate as to whether: A) the workers had not bothered to pull up ("hook") the mesh because no one was looking; B) they hooked the mesh too close to where they were standing on it; or c) the mesh settled before the concrete set up. Every report I wrote for design of new construction (literally thousands of acres of housing) recommended that the mesh be supported at mid-slab height.

I've seen guys at work lay the mesh on stands made for the purpose and even rocks. Hopefully that will keep it in the center. (If enough are used so the mesh does not bow down between supports)
People think the wire stops cracking. As I understand it, the wire (hopefully) keeps the cracked pieces from separating. I could be wrong.

Kudos for good work. However, sand compacts more easily and denser using vibration. As good or better result could have been achieved faster, and therefore cheaper, using a vibrating compactor on just 2 lifts (3 to be really conservative). This is especially important to understand for sand in utility trenches. For trenches, the worst way to compact sand is jetting.

In our case, it was plate compactor that did the work (Vibrating) on the good area. Layer by Layer. Repeated passes in two directions and at an angle.

 

[tomtheelder2020]

In our case, it was plate compactor that did the work (Vibrating) on the good area. Layer by Layer. Repeated passes in two directions and at an angle.

If that contractor is still in business, give him a Yelp review. Great work deserves accolades.

 

[PJB12]

If that contractor is still in business, give him a Yelp review. Great work deserves accolades.

That's a very thoughtful idea, tomtheelder202!
Paul