I am a general contractor and have

[STEELMANROCKS]

I am a general contractor and have been pouring concrete for several years. On a recent pour, I ordered the concrete with truck intervals of 30 minutes apart. The daytime temperature was approximately 70 degrees. Due to delivery problems which resulted in delays in delivery of up to 2 hours, cold joints resulted. slab contained welded wire mesh and was poured 4 inches. Because of customer concerns, customer wants the slab removed and repoured. There are 3 questions:
1. how would this unplanned cold joint effect the structural integrity of the slab?
2. Is there an ACI Code that specifies or limits the delivery intervals that a redi-mix company must adhere to?
3. We agree with the customer that the time it took to deliver each concrete batch was unwarranted and that the resulting slab finish is unsatisfactory, The Concrete company has refused to assume any responsibility for the delays that resulted in unplanned cold joints. are there any suggestions that would force the company to assume this responsiblity? or any suggestions as how to correct this problem short of removing the 60 x 80 slab?


MARKFORBES@FORBESSTEEL.COM

 

[jheidt2543]

You don't say if this was a structural slab or a slab-on-grade. I am assuming that it is a slab-on-grade because of the mesh reinforcing you mention. If it is a slab-on-grade, I don't see how a cold joint can be much of a problem. We used to checker board the pours, each panel being a cold joint.

If the edge of the slab is an irregular cold joint, I would chalk a line back from the edge and saw cut through the entire slab and remove the bad edge. Then pour back what is needed to repair the edge - it should be no problem. If there is a concern about load transfer then dowel the slabs together. But, this is a 4" slab, so that shouldn't be a big concern either, since you shouldn't have much of a loading anyway.

Removing the entire slab, based on your discription, is a waste of money.

 

[SperlingPE]

There is an ACI code that addresses delivery/mixing time for concrete. The code addresses the delivery time during hot weather placement of concrete. I believe the normal time is 60 minutes and during hot weather the time is reduced to 45 minutes. This is the time from the plant to when the truck is emptied (not when it arrives).

 

[dirtdoctor]

Any reputable concrete company would own up to this screw up. But, have to agree with jheidt that ripping up the slab is not warranted. As far as a poor finish, get a top coating or epoxy surface treatment to pretty it up.

 

[Qshake]

As noted by the other posters, there are guidelines, specifications and industry accepted standards for the acceptance of concrete for placement.

It seems, from your description, that the supplier failed to meet the specifications required by you (contractor). As such, since the supplier has a duty to you (i.e. furnish concrete within a reasonable time of that stipulated in your agreement) and has failed to make good on that duty is responsible for the poor product. This, of course, is noted without mention of whatever clauses that the supplier has on any agreement it enters with contractors.

So, noting the above it would appear that some persistence with legal action is in order to force the concrete supplier to pay up (partial or full). I imagine that they've seen this a few times (nature of the beast) and treat each case the same way hoping each will go away. Only those that are persistent are pursued.

As for the quality of slab, the durability and therefore the longevity of the slab is in question especially if the finish is in question. Its not just about bad looks. I agree that the slab is not likely structural, but that doesn't mean the owner should settle for less of a product that what was ordered.

As for what to do, there will undoubtedly be several things noted. Some mentioned by other posters. Leave in place and take a refund. Place a new and seperate thin finish on top (something I've never seen work to date as they usally crack). Cut it out and replace it. The likelihood of the latter being implemented is rare. However, I'll be willing to bet someone will suggest the concrete be tested to ensure its appropriate properties and that along with the lawyer fees will be over and above the expense of replacing the damn thing from the start!

Good Luck.

 

[dirtsqueezer]

STEELMANROCKS,

From the sounds of it, you are fighting the good fight. You need paperwork and code references if you are going to handle this properly. I don't know what code applies to you, but you probably have the '97 UBC and possibly even the plans themselves to fall back on. I don't know of any specific ACI codes on delivery, but locally, our jurisdiction gives concrete trucks 1.5 hours to pour out.

Let me ask you, did you have a special inspector? I'd hate to go against one of my own, but if they allowed the pour or don't have their paperwork in order, you might be able to go after them. Let say also that have no fear, your slab would be structurally compromised. Joints through a steel connection allow water to wick in. When the steel rusts, it expands, and it has pretty good potential to crumble your slab in a short amount of time.

It sounds like you have good intentions! Don't let this supplier drag you down. I think a quality company will always outlast one that's not, even if it's just from the joy of good work. Good luck.

 

[gauger]

You do not say where you are, but we have hot weather in Oklahoma, 70 degress is not that bad but for quality, the concrete should be in place within 45 min. of the introduction of water in mix.
Similar concrete finishing problems happen here during hot pours. Bad things happen to structural concrete when the Portland Cement content sets before it is spread out in a pour.
Concrete shrinks as it dries and has low strength, especially tensile strength, when the cement is dead. Bad finishes,and very low performance properties are almost assured. This often shows on the surface, as dimples, rough or uneveness, and cracks.
On those occasions we sometimes avoid the problem by not introducing mix water until the load gets to the job site. When normal mix water is introduced we even resort to replaceing some of mix water with ice to keep the load cool.
A slab on grade with 60x80 dimensions should be broken into panels with expansion-contraction joints,in order to reduce the movement and not overload the reinforcement. The minimum reinforcement should be sufficient to drag the weight of half the panel width across the ground in each direction.
Obviously E-C joints would simplify decisions about where to start or stop removing bad areas of slab. Capping the surface with a thin slab has never worked for me, except for small areas (4'x4') with special concrete and special bond enhancers on a slab that is not cracked.
So much for the lecture, the ACI Code has mix design requirements and handling procedures and time limits, usually in relation to the temperature. Portland Cement Company provides numerous manuels that are commonly the basis for "Recommended Good Practice" for concrete work.
I have never heard of construction documents or contracts that specify the delivery intervals, that would be the contractors choice, determined by the ability of his crew to handle each load into place and finish it.
The concrete company has responsibilities for a reasonable design if one was not specified. In my opinion they are responsible for the product until it arrives at the job. You should obtain and review written standard operating practice, or limitations of liability either as published company standards or on the sales contract.
The concrete company also would normally record the time truck left the plant, and the time the load arrived at the job, as well as when delivered. This information may be on their delivery tickets, and may be part of your records. You may have received a copy from the driver and maybe a copy with their billing.
In my opinion, you are responsable to the owner for the job according to the contract with him. The concrete company is responsable to you for the product as determined by the purchase contract.
The job repair might be expedited by sawing the slabs into panels and replacing the bad ones. The cuts should, probably, be of uniform spacing determined by the size of the welded wire fabric as noted above.
I am not a Lawyer, this informaion is from my experience as an engineer.