Sidewalk Flag Drying Too Slowly?


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Old 02-02-09, 10:47 PM
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Question Sidewalk Flag Drying Too Slowly?

New York City

Some guys replaced a sidewalk flag today. They poured it around 10:30 am. I didn't see what kind of mix they used.

At 7pm I tested the flag with my finger. It was almost as soft as room temperature butter.
At 8pm the flag was still as soft as butter left out of fridge an hour might be.
Air temperture reached high of 54 F today.
Air temp 7pm was 40F.

At 12:30am next day, flag was still soft to the touch with a finger. A small depression could be made with slight pressure. It felt kind of sandy.
Temperature/Humidity at 11:51 update (NWS): 36F, 70%

Seems like it's drying too slowly to me. What you think?
 
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Old 02-03-09, 10:38 AM
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You should quit touching it.
 
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Old 02-03-09, 01:45 PM
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Do you know that the concrete in Hoover Dam (Boulder Dam) is still curing, and it was built in 1935?
 
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Old 02-03-09, 01:57 PM
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Chuck Yes..I did know....since I drive over it every few weeks..lol.

Tom..we're just messing, but they probably know what they're doing, or they wouldn't be allowed to do it. Concrete curing slowly is a good thing, from what I understand of it.
 
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Old 02-03-09, 06:48 PM
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Originally Posted by Tscarborough
You should quit touching it.
Well I'm not the only person who's "touched" it. It has gotten damaged in a couple of places by what looks like a wheel. Perhaps from a cart of some sort. This occured around 7pm last night and from the indentation, it looks like the concrete was still quite soft.
 
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Old 02-03-09, 06:53 PM
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Originally Posted by Gunguy45
they probably know what they're doing, or they wouldn't be allowed to do it.
I've been in the construction business for over 30 years, although not in the concrete end of things, and your assumption is not one I would make.

They didn't ask me if it was OK to do it, and it's on my property. I would have had a few questions to ask about curing times, antifreeze, and final strength in a cold weather pour if they had.

By the way, the company that's doing this is the same company that poured the same flag some weeks ago that I did not accept. At that time, they put a plastic tarp over the flag immediately after the pour which settled into the cement and left wrinkle impressions of the plastic in it.
 
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Old 02-03-09, 07:02 PM
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It started snowing today around 3pm, approximately 1 day after the pour.

At 6pm the temperature is 28F and humidity is 78%.

At around 6pm, the cement is still soft to a finger touch. Some garbage pails that were originally around the flag with caution tape have somehow all gotten moved onto the flag which is covered with snow, perhaps by a person who shoveled the sidewalk around 4pm. I don't know if the pails marked up or scratched the cement yet. But based on how soft it still is, I wouldn't be surprised.
 
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Old 02-03-09, 07:10 PM
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Well, I'm not familiar with NYC..but is this a city contracted company? Why are they working on your property? Area's I've lived..the sidewalk is city property..and they either have their people do it, they contract it, or it has to be approved by them.

If you have concerns, shouldn't you be calling the city?
 
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Old 02-03-09, 07:23 PM
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You will have to define what you are saying. "Flag" denotes grouting/laying flagstone, which is not concrete. Exactly what are you talking about, and pictures help.

40 degrees and rising is the generally accepted standard for placing concrete or laying rock, and so long as initial set occurs before freezing (generally considered to be around 12 hours), crystallization/freezing is not normally a problem. The hardness of the material is irrelevant, but access should of course be limited.

Exactly what field is your 30 years of construction experience in, just out of curiosity. Poking your finger into others work?
 
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Old 02-03-09, 07:26 PM
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Question

Originally Posted by Gunguy45
but is this a city contracted company? Why are they working on your property?
What does it matter who contracted them or why they are doing it? I'm looking for technical advice on concrete, not administrative or legal advice on who to contact.

Maybe the city building department has someone that can advise me on proper concrete pouring practice, I suppose. But is there no one here with similar knowledge that can?

I can bring it up with the contractor if need be.

The question is: are they following good workmanship practices or not.

Another question is: is it normal for a sidewalk flag to still be soft 30 hours after it's poured?

I don't think so, but I'm not a cement expert.

I don't know. That's why I asked the question here. I thought there might be someone in this forum with that knowledge.
 

Last edited by TomBrooklyn; 02-03-09 at 07:43 PM.
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Old 02-03-09, 08:10 PM
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Sidewalk Flag Drying Too Slowly?

You are definitely not a concrete expert or even close. Most masonry sidewalk material are laid in some sort of mortar ot grout. You are apparently not "pouring concrete" unless you are dealing with stamped or embossed concrete. The "flag" (if it is a stone) does not get soft. Any cementitious material will not cure at lower temperatures without extra required curing and insulation.

You will be hard pressed to use the pressure techniques anywhere that are enforceable by code for your application and materials. - You were also referring to the air temperatures that have a long term effect on the temperature of the materials used. Did you buy and supervise the storage of the materials?

Anybody that has been around construction for 30 years isn't necessarily an expert construction, but should know by now that that in different conditions, materials act depending on temperatures and humidity. - Paint dries slower, drywall joints cure slower and concrete cures slower when the temperature is lower and the relative humidity is high.

Any reasonably intelligent contractor should know this and direct the subs accordingly for conditions and protecting when awarding a contract.

Common sense for someone in a cool climate should also know this before be blames a contractor that may have been chosen (possibly without references) because he is cheaper.

I am also curious - What exactly is the "sidewalk flag" since it is not at all common term or descriptive of the materials and properties?

Sounds like a DIYer buying labor for installation and crossing his fingers or hoping he has a relative that is an attorney and collected politically in Brooklyn.
 
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Old 02-03-09, 08:26 PM
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I've heard the section of concrete between two joints called a "flag" before. In my opinion, it should not still be that soft after 30 hours, but it all depends on the mix they used. My guess is that since it was only one "flag" (probably about 4x4 or so), then they probably mixed up some sakrete and poured it. It is too small to buy it from a ready mix plant. If that's the case, it's also possible that they mixed it too wet and that the low temps are causing it to set very slowly. However, this is all just conjecture. As long as it's kept from freezing, it should eventually set up plenty hard. If you're that worried about cosmetics, my guess is that this one won't meet your standards either, even though it may be structurally sound.
 
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Old 02-04-09, 02:17 AM
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Originally Posted by Concretemasonry
You are definitely not a concrete expert or even close.
Yes, I stated that. You are definitely not a gentlemen or even close.

Originally Posted by Concretemasonry
You are apparently not "pouring concrete" unless you are dealing with stamped or embossed concrete.
Around here, when you put concrete in a sidewalk, or most other places, it is called pouring. Just a term.


Originally Posted by Concretemasonry
The "flag" (if it is a stone) does not get soft.
Around here, one square of cement sidewalk, defined by the perimeter control joints, approximately 5' x 5', is called a flag.

Originally Posted by Concretemasonry
You will be hard pressed to use the pressure techniques anywhere that are enforceable by code for your application and materials.
I don't know what you mean by pressure techniques.

Originally Posted by Concretemasonry
You were also referring to the air temperatures that have a long term effect on the temperature of the materials used. Did you buy and supervise the storage of the materials?
I noted temperatures because they are obviously relevant. I had nothing to do with the purchase of materials or supervision of the job.

Originally Posted by Concretemasonry
Anybody that has been around construction for 30 years isn't necessarily an expert construction, but should know by now that that in different conditions, materials act depending on temperatures and humidity.
Right. I'm also an engineer so we can get a little perspective here. But I didn't need to become an engineer to know about temps and drying. I learned that in 4th grade science class. But still, none of that makes me an expert on exactly how fast concrete dries at certain temperatures and humidity.

I am aware there are different kinds of mixes of concrete and additives that can affect drying time very dramatically. I know there are mixes that dry very fast. I don't know, however, what mix was used on this job. I just know how it is turning out. It would appear it was not a fast drying mix.

Originally Posted by Concretemasonry
Any reasonably intelligent contractor should know this and direct the subs accordingly for conditions and protecting when awarding a contract.
Your point is what? Did the contractor make a mistake? That is my question from the get-go, as I suspect he did.

Originally Posted by Concretemasonry
Common sense for someone in a cool climate should also know this before be blames a contractor that may have been chosen (possibly without references) because he is cheaper.
So now your point is that if I hire the contractor with the best price, I have no right to expect good workmanship and reasonable standard working practices?

Originally Posted by Concretemasonry
Sounds like a DIYer buying labor for installation and crossing his fingers
That is not the case, and I will refrain from describing what you sound like by this point in your post.

I don't know what your motivation for your whole reply so far has been, but if you have any actual expertise in concrete techniques that can shed some light on good workmanship standards etc., I am listening.
 

Last edited by TomBrooklyn; 02-04-09 at 03:22 AM.
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Old 02-04-09, 07:57 AM
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Sidewalk Flag Drying Too Slowly?

Apparently you have a different terminology than most of the concrete people in the country. Concrete is placed and not poured. Many people think the "flag" is flagstone that is set in sand or concrete (depending on situation) and grout may be used around the actual stone.

Concrete does not "dry out". It cures and the curing requires moisture or the strength gain stops. I learned this in 1960 while studying engineering and before I was a bridge and concrete inspector and before 40 years professional experience in concrete and concrete products.

You just have a concrete sidewalk that was not protected immediately after it was placed. It should have bee placed on unfrozen soil and protected from freezing and drying during the first few days, depending on the climate. It also should have been air-entrained to increase the freeze/thaw durability. Your city or local code could be a guide whether is should have been used.

I have been around and lived in your part of the world (from Philly to Providence and understand that "pressure" is a common tool used to get enforcement (if required). I had to deal directly with engineers, contractors and unions and saw it (pressure) daily.

If this is a city sidewalk, there are city specifications for materials, practices and contractor licensing. - If it was on private property, the materials and practices should be covered by your contract if you had one or between you and the contractor if you did not have one. Again, city specs could be a guideline.

As far as using any national codes and standards, you will have a hard time getting satisfaction unless it is big enough to warrant getting and attorney involved. When we write the national codes and specifications, there is some provisions for local materials and practices appropriate to the job as long as they are referenced in the contract.

You had the same contractor do it that did unacceptable work earlier? That is a red flag to ask questions and watch carefully during construction.
Dick
 
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Old 02-04-09, 12:14 PM
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Hi Dick,

The term "poured" is usually used around here, but that is by laymen or construction personnel not specifically in the concrete business so it may not be technically correct term even around here. Anyway...

This is the sidewalk in front of my house. I think the city owns it, but the homeowner is responsible for it. I was responsible for the incoming water service pipe that had to be replaced which was why that one "flag" section was broken out in the first place.

My question however, is not to try to determine who is responsible. I am paying for the job and I will hold the contractor responsible. Since I hold the money, that ought to give me quite a bit of say, regardless of who is officially responsible. Again, that is all besides the point.

What I am asking here is more along the lines of...

1. What is a reasonable standard of workmanship that can be expected?

2. Is it reasonable to place concrete on a cold day with snow in the forcast? If so, would it only be considered reasonable and good workmanship if a special fast curing or low temp curing mix is used?

3. Is it reasonable to place a mix on a fairly busy with foot traffic sidewalk that remains as soft as room temperature butter 7 hours after it is placed? So that it is still soft after it gets dark and people might stumble into the edges of it (as is what actually happened despite it being cordoned off.)

By the way, between 7 and 8 hours after it was placed, a cat stepped on it and left a paw print. Is it normal for it to cure that slowly?

This is a small residential job. There were no written detailed specifications made for the concrete. Therefore, however, I believe reasonable good workmanship standards should prevail.

Perhaps the city has some guidelines that would make sense to apply here. I'll check that out.
 
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Old 02-04-09, 01:45 PM
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Contractor just came and looked at the flag/slab.

When I answered the door the first thing he said after he said "hi" was "the slab had to be replaced, don't even worry about it."

The purpose of my post was to familiarize myself with what would be considered a reasonable expectation in case there was a dispute. There was no dispute. Issue over. Thanks.
 
 

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