Pouring Concrete Sidewalks in 100+ Degree Temperature

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Old 09-01-11, 01:11 PM
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Angry Pouring Concrete Sidewalks in 100+ Degree Temperature

My community (located in the Dallas metro area) recently had a construction company install some concrete sidewalks. The concrete was poured (on tamped dirt without a sand/gravel base but did have rebar) and finished on a day when the temperature was over 100 degrees with full sun. I fully realize that pouring concrete in high temperatures is okay, but I certainly expected that the sidewalks would have been kept damp so the concrete would cure properly. At no time were the sidewalks ever dampened or wet-down to slow the curing process. Needless to say these sidewalks now have numerous cracks (see video link below) from the concrete curing too quickly. These cracks are in the areas of the sidewalk between where expansion joints and where control joints were cut...in other words the cracks are located in the open (finished) areas where there should be no cracks 'if' the concrete had properly cured.

I've been around construction jobs for decades, from small jobs to mega jobs valued at over $1 billion, and I have never seen concrete not kept damp/wet during the first 72 hours or so [especially] when the temperatures are above the 70s. And when the temperature is in the 90s and 100s it becomes critical to keep the newly poured concrete damp/wet so moisture is not drawn from the concrete too quickly.

Anyway, we now have newly installed concrete sidewalks that have numerous cracks (which looks bad), but equally important is the concern that the concrete will not hold-up over the years as it should...which poses a few questions.

Should the construction company have kept the sidewalks damp/wet to prevent the concrete from curing too quickly?

How many days should the concrete be kept damp/wet if the nighttime lows are in the mid 80s and daytime highs are 100+ degrees with full sun?

Should the construction company be made to demolish and re-install the sidewalks 'properly'?

In the meantime the construction company that installed the sidewalks tried to 'repair' the cracks using a concrete crack repair product, which looks terrible and probably won't last (in my opinion). But in my opinion this doesn't address the fact that the concrete did not cure properly and will likely result in future cracks and failure in the short term. Is this correct, or not?


Video that a neighbor made: 2011-08-26 Crummy-Crumbling-Cracking Sidewalks - YouTube

If some of you concrete 'experts' would answer my questions and offer your suggestions on how this should be handled I would greatly appreciate it. Thank you.
 

Last edited by paperchase; 09-01-11 at 02:08 PM.
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Old 09-01-11, 03:38 PM
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That video is terrible quality. It's hard to see anything. You should be taking hi-res digital pictures of the issues involved. Use a timestamp as well for use as evidence. I'm not a concrete expert, but I think you are right. They should be replaced. Last fall there were some new sidewalks installed here in my town. I don't know what th reason for the problem, but there were some areas where the walks flaked off on top. Come spring, those sections were removed and replaced. You can't repair that kind of thing.

Concrete needs water to cure. Keeping it wet in hot conditions doesn't slow the curing process, but ensure that there is water available to the concrete so it can cure.
 
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Old 09-01-11, 04:41 PM
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From the video, I did not see anything relating to curing.

Was a curing compound applied instead of the traditional "keep the surface wet" philosophy?

The cracks did not look like shrinkage cracks.

There were some cracks that looked more structural and due to settlement or expansion.

What was the condition of the soil (compaction and especially moisture before placing the concrete? The soil may have expended due to the available moisture from the concrete.

Since the orginal post just asked more questions than provide information little more can be offered.

Dick
 
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Old 09-01-11, 04:58 PM
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It looks bad.
Concrete can be poured in hot weather. There are plenty of additives to use, if you want to spend the money. However, even so the base should be dampened first, the concrete should not be poured excessively wet, the joints should be hand-tooled instead of sawcut (because in temperature extremes, concrete will crack before you can come back and saw it), and a liquid cure-n-seal compound should be sprayed on immediately after finishing. If a cure and seal is not used, then you should keep the concrete wet for at least a few days.
In addition, joints need to be at least 1/4 as deep as the concrete is thick. They should cut the slab into roughly square sections. No section should be more than 1.5 times longer in one direction than it is in the other direction.
The cracks were inevitable, but they could have been controlled with proper finishing practices, subgrade prep, and curing.
Perhaps the crew was under-manned or they tried to pour too much at once and it got away from them. Perhaps the general contractor took the lowest bidder and he got what he paid for. Who knows?
It should probably be removed and replaced, but if you're not in a freeze/thaw climate, it probably won't get much worse over time.
I found it interesting that the stamped concrete seemed to have almost no joints. That's certainly a no-no, but in the videographer's opinion it looks better than the newer concrete.
At the start of the video, there should have been a joint cut to the metal water casting. Anywhere there's a slab penetration, the slab needs to be jointed.
 
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Old 09-01-11, 05:26 PM
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Originally Posted by Pecos View Post
Perhaps the crew was under-manned..........
Great info, Pecos, but, in all reality, where have you ever seen a DOT jobsite "undermanned"??? Here in Georgia, there are 2 engineers, 6 supervisors and 4 guys doing the work. And that is to repair a sidewalk section. We won't even get into road repairs. It is almost a joke around here. Perpetual job security.
 
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Old 09-01-11, 06:44 PM
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Originally Posted by Concretemasonry View Post
From the video, I did not see anything relating to curing.

Was a curing compound applied instead of the traditional "keep the surface wet" philosophy?

The cracks did not look like shrinkage cracks.

There were some cracks that looked more structural and due to settlement or expansion.

What was the condition of the soil (compaction and especially moisture before placing the concrete? The soil may have expended due to the available moisture from the concrete.

Since the orginal post just asked more questions than provide information little more can be offered.

Dick
Dick,

The soil was extremely dry (practically no rain and 100+ degrees days for 3 months). The soil was tamped with a relatively lightweight tamper before the pour. No post-pour curing compound was applied.
 
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Old 09-01-11, 06:56 PM
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Originally Posted by Pecos View Post
It looks bad.
Concrete can be poured in hot weather. There are plenty of additives to use, if you want to spend the money. However, even so the base should be dampened first, the concrete should not be poured excessively wet, the joints should be hand-tooled instead of sawcut (because in temperature extremes, concrete will crack before you can come back and saw it), and a liquid cure-n-seal compound should be sprayed on immediately after finishing. If a cure and seal is not used, then you should keep the concrete wet for at least a few days.
In addition, joints need to be at least 1/4 as deep as the concrete is thick. They should cut the slab into roughly square sections. No section should be more than 1.5 times longer in one direction than it is in the other direction.
The cracks were inevitable, but they could have been controlled with proper finishing practices, subgrade prep, and curing.
Perhaps the crew was under-manned or they tried to pour too much at once and it got away from them. Perhaps the general contractor took the lowest bidder and he got what he paid for. Who knows?
It should probably be removed and replaced, but if you're not in a freeze/thaw climate, it probably won't get much worse over time.
I found it interesting that the stamped concrete seemed to have almost no joints. That's certainly a no-no, but in the videographer's opinion it looks better than the newer concrete.
At the start of the video, there should have been a joint cut to the metal water casting. Anywhere there's a slab penetration, the slab needs to be jointed.
Pecos,

Thanks for the information and advice.

I just hate to pay for workmanship that is not up to [even] normal standards. In this case the work already looks terrible...when it should be looking its best.

I agree, the stamped sidewalk needs control joints just as much as the sidewalks with a regular finish.

Are the sidewalks with the cracks bad enough in your opinion to demand they be torn out and replaced?

PS - The sidewalks were poured on Saturday, August 20th and every day it has been over 100 degrees. We had a brief little shower about a week after they were installed.
 
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Old 09-01-11, 07:01 PM
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Here's another video my neighbor made after the contractor tried to fill-in the cracks. It may help you tell more about the quality of the workmanship and what we have.

Again, I need advice on whether the less-than-desirable sidewalk(s) should be accepted as-is, or be replaced. Please advise your opinion.

2011-08-31 Hiding The Cracks - YouTube
 
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Old 09-01-11, 08:02 PM
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Only you can decide whether or not to pay the guy. I'd like to go back to one of my earlier points though. How did you pick this contractor? Did you go to some of his previous jobs and look at them or did you hire the cheapest guy you could find? Caveat Emptor, and all that.
Aside from the cracks, the finish is like nothing I've ever seen on new concrete. What are all the black dots? Is it textured or is this a rock salt finish? Hard to tell by the video.
 
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Old 09-01-11, 08:34 PM
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Originally Posted by Pecos View Post
Only you can decide whether or not to pay the guy. I'd like to go back to one of my earlier points though. How did you pick this contractor? Did you go to some of his previous jobs and look at them or did you hire the cheapest guy you could find? Caveat Emptor, and all that.
Aside from the cracks, the finish is like nothing I've ever seen on new concrete. What are all the black dots? Is it textured or is this a rock salt finish? Hard to tell by the video.
Pecos,

Our property manager received 3 bids for installing the sidewalks and I believe they were all very close in price. I do not know whether there were any 'real' specifications...other than location, sidewalk length, width, thickness, rebar, and surface stamping on the one walk. I believe the property manager has used this contractor before on other projects.

The surface is broomed except for the stamped walk. The black dots (as you describe them) that you see in the close-ups in the video is actually dirt and debris from all the nearby work on the irrigation system.

There is obviously a lot of surface or plastic shrinkage that has caused those cracks. I feel it could have been avoided. I guess I'm looking at the job from a standpoint of whether a general contractor or architect would accept it...if the project was for ATT, Coca-Cola, Boeing, etc. Or if the owner of a $3 million house would accept it. I think I know the answer - hell no, it wouldn't be accepted.

I fully understand that we (multiple homeowners) are the ones that must ultimately decide whether to accept the sidewalks as-is or have them redone, but I wanted to hear what a concrete contractor (an 'expert') that takes pride in their work would think is fair and reasonable...for less than a satisfactory job.
 
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Old 09-02-11, 04:58 AM
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I couldn't even tell that the sidewalk was broomed from the video. It looked like it was simply floated and had a lot of pock marks and other imperfections in it. As drooplug said, the picture quality is so poor that we can't see what you see. I can't really give an opinion without actually seeing it.
If you think it's bad enough to tear out and redo, then that's what you should do. Beauty (or hideousness) is in the eye of the beholder. I've done jobs that I didn't like and the owners loved them. I've also done near-perfect jobs that the owners nitpicked and complained about.
 
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