"Hot" Concrete Placed in Residential Foundation 2

[Colostruct]

Last night I got a frantic call from a homeowner/client who is a civil engineer about his new house foundation I designed.

Evidently, the concrete subcontractor placed the last truck at 3 hours out from the batch plant, placed it, tried to trowel the surface and left when it started raining. I took a look at it and could not believe how bad it looked. The concrete was too hot to strike off at the tops of the forms and too hot to place anchor bolts. Top varies up to 2" in elevation. Walls are up to 9 ft. high.

I'm meeting in an hour with the GC and owner. I've never encountered this level of poor craftsmanship in 35 years as a PE. My gut reaction is to say rip it all out and start over. But, is this knee jerk? I'm not sure how to even start repairing it. And, no matter what they've done, I will be responsible for the integrity of the foundation once I try and come up with a repair.

My expertise is on new construction, big retaining walls, and historic restoration. When I've dealt with modern structures with deficient concrete I've called in rehabilitation experts. On a new residence, would it be appropriate to tell the GC he needs to get his own consultant? What would any of you guys do here?

 

[JStructsteel]

I would put it on him. Present the data, use the batch plant tickets, and tell him you want a letter saying its ok, and that there will be no performance issues. That way you dont have to foot the bill either.

 

[RabitPete]

Wondering how well it was consolidated, if at all. You might be out for another surprise once the forms are removed. If I were the homeowner, I would insist on replacing the entire thing.

 

[hokie66]

I would not accept that. Letters won't help. Jackhammers to the ready.

 

[phamENG]

If I were inclined to be nice to the GC, I might opt for coring the footing to test it. Might.

 

[RabitPete]

Just to clarify, are we talking about 9ft tall basement walls, or spread footings which will have a 9ft framed wall on top?

 

[Colostruct]

Thanks for the comments! These are the stem walls. The tallest walls are 9 ft but only retain about 5 feet. Soils are text book perfect...mountain Valley gravels. Old buildings last 120 years so far on stone foundations. So, it’s hard to tell someone to rip out a $40 k foundation on a 1800 sq ft. House.

IF this was one of the resort mansions over the hill in Telluride I design this foundation would already be under the jack hammer. But, that wouldn’t have happened there because GC s there wouldn’t let it!

I asked them to leave the forms on for another day to avoid curing issues (it can freeze anytime) so I haven’t seen the consolidation.

These guys also claim they always grind the tops of walls rather than finish them...that’s why it’s so rough. Is this for real? I’ve worked with a lot of concrete contractors and none of them do this. I’m sensing some major BS going on.

 

[Ron]

Agree with hokie66. Don't waste time trying to placate everyone. Reject it and make them do it over...correctly this time. Apparently you are in California and working either directly under the IBC-R or a California subset of same. ASTM C94 is one of the referenced standards, which under Chapter 1 of the code, invokes the full standard as if it were written verbatim in the code. This means that if you violate the standard, you violate the building code. Placement of concrete that is 3 hours old is a violation of C94 and thus, the building code. Tear it out.

 

[Colostruct]

Colorado. But, my spec is ASTM C94. The Building Official won’t give them a CO unless I approve any repairs. I can ask them to remove it...But, this will get ugly.

 

[Enable]

Maybe it's because I am a contractor but I may be a bit more forgiving in the sense that, if it works as it stands no need to stand on a high-horse and tell them to rip it out. Sounds like that would be annoying for you anyways.

I know the answer to this before asking but just to be sure, did they have a retarder in the mix? Was it poured in hot or cold temps? My immediate reaction to 3 hours after batch is that is not terrible depending on ambient conditions + admixtures. I mean, code typically gives us 2 hours and/or by revolutions. 3 hours in colder temps aint so bad.

Though the reason they gave you for why the top is so out is utter garbage. It's easy to strike off the top of a form and 100% what anyone would do. Actually I raise my forms a bit and nail a finish strip so I know exactly where my line is to be. Works soooo nicely compared to grade nails / eyeballing. So long story short they fucked up. But I'd still wait until the forms are removed to make a decision. If it's honeycombed to shit you have your answer (rip it out). If it looks okay then core it and see what the strengths are + any interior layering that may exist. If that looks good and the top is really the only fucked part, tell them to chip a few feet + dowel in some bars and pour an SCC top course. I say SCC because they are dopes that cant finish clearly.

EDIT - Fun residential concrete story. So I was building a monster custom home, as the GC, and asked what concrete the forming guy wanted. He said: "dont worry send the typical mix and we will make it a corner to corner slump". Joking, I think. But not really, residential is a entirely different brand of terrible. Anyways, I said fuck you and ordered 150mm C1 with super-p. His forms took a beating / deflections were a bit lets say...out of range...but my concrete looked mint otherwise!

 

[MTNClimber]

Enable nailed it. I remember in my first year out of college being the concrete inspector on a job for a new slab in a historic structure owned by a Ivy League university. The pour took 4 hours and… all of the concrete trucks arrived within the first hour. I immediately told the GC that this was not going to end well… The last truck needed so much water that, after he emptied his tank, they brought over the guy that just finished washing out to add some of his water to the truck. Luckily, I had an extra set of cylinders so I sampled the last truck. Shockingly the concrete ended up breaking at the specified strength, the structural EOR was fine with it, and no one said a peep about cracking or other slab performance issues.

So I concur with Enable. See what it looks like after the rip the forms and do some cores to see if it has strength before rejecting anything.

 

[Canuck65]

It is not all just about strength, there is a durability component to it as well. The Owner did not receive what they paid for, i.e. concrete that was clearly out of specification. However I don't think that you can complete your evaluation until a) the forms are removed for a visual inspection, b) some additional testing is completed. After the evaluation is complete, you will be in a position to accept or reject the foundation walls. You have now spent time dealing with this issue, which I presume you will be invoicing the client, plus any additional testing will cost money, plus this is now putting the project behind schedule. The contractor should be responsible for these costs. There also should be an additional credit to the Owner for accepting the risk of a potentially inferior product that didn't meet spec. If the contractor doesn't accept financial responsibility for an inferior product, then have them rip it out and redo it.

With respect to the uneven finishing of the top of the wall (if it is not ripped out), I have never heard of this excuse for poor workmanship, it is an absurd statement. It leads me to believe the contractor does not know what they are doing. Before they start grinding or cutting, you should be clear what the requirements and tolerances shall be. No payment until it meets the specifications.

 

[Colostruct]

Thanks all for the input.

They are removing the forms tomorrow. I just received the mix tickets. The last load was 3:45 old at discharge and 4:15 minutes when they were trying to strike off the top to elevation. They were unable to install anchor bolts. The site is at over 9000 feet in elevation (so cool) and it was mostly cloudy at the end of the placement. This crew was not familiar with construction in the mountains and there were issues with delays on the mountain passes getting to the site. They were batching trucks 20 minutes apart and the crew needed an hour each truck. No room for error.

I built my own house in this town 25 years ago and did my own foundation. We truck mixed the concrete and it worked great. Now, that technique is frowned upon and the batch plant won't do it. Instead they rely on retarders and placements that have enough crew. This crew was, clearly, out of their element.

The client is a civil engineer who does large municipal projects. He is pretty upset. I'm afraid no matter what it looks like he will not be happy. At this point, my approach is to notify the contractor that they are out of specification and code and:

1. There may well be durability issues although there is little exposed concrete.
2. I will recommend that the exposed wingwall retaining structure be replaced. I don't even care what this looks like down in the forms...the top looks more like gravel than concrete and a repair will look like s__t and durability is compromised.
3. The tall wall anchor bolts ARE important and I don't trust that concrete regardless of what it looks like since it was 4 hours old at placement. So, I will recommend that they remove that concrete and repair or provide an alternative restraint connection and alternative hold downs to avoid stress concentrations on locations with, potentially, poor consolidation. I will have to see what the consolidation looks like especially in this area.
4. We will core test in enough locations to ease any concerns with overall structural capacity.

The contractor wants me to bill him. I won't do that BTW. It is my opinion that this crosses the line into means and methods. Plus I've done this on framing issues (utility penetrations) and the contractor stiffed me. Since this is a residence, it is my opinion that I can only make recommendations to the owner and it is up to him to decide how to proceed if there is not clearly an issue with structural stability. On a commercial or multifamily building I would bring in the Building Official. It would be unlikely we would get here with the Special Inspection requirements of the code for those buildings.

My usual work is high dollar residences and mixed use commercial buildings with multi million dollar condos in a resort town. Everything is "by the book" in that environment. Honestly, it has been a decade since I have had a quality issue on a project (Banging head against wall for taking on a small residence...)

 

[BigH]

One question - why so long between batching and placement? Traffic jam (doubtful) - too far away?? Just wondering

 

[Colostruct]

One question - why so long between batching and placement? Traffic jam (doubtful) - too far away?? Just wondering

Remote location and road work. This batch plant is 90 minutes away by truck. There is a closer plant that is 60 min. out. The guys used to working here use that plant to buy another 1/2 hour. That with retarder and early AM placements usually do the trick. Lack of experience.

 

[RabitPete]

Grinding the top is a not a common way of doing it, unless its a big screw up. Nobody grinds 2" off!
Homeowner has the final say, I've seen picky homeowners threatening to refuse to close on the house quite a few times. Issues ranged from the new concrete on the driveway starting to spall to studs with larger than normal knots and tree bark. It's up to GC and contractor to resolve the issue and to decide who will foot the bill. In most cases contractor wants to keep GC happy for the sake of future business and will cover the cost.

 

[Rabbit12]

My 2 cents. If I was the homeowner I'd be a bit reluctant to accept this. It may be ok now, but long term durability and performance concern me. The GC and contractor will be long gone by the time those issues show up. You say that the concrete was too hot to strike off and too hot to place anchors. What does that mean? Like they literally couldn't touch the concrete? Were they going to wet set the anchors?

Ultimately it's an uncomfortable spot for an engineer.

 

[Colostruct]

My 2 cents. If I was the homeowner I'd be a bit reluctant to accept this. It may be ok now, but long term durability and performance concern me. The GC and contractor will be long gone by the time those issues show up. You say that the concrete was too hot to strike off and too hot to place anchors. What does that mean? Like they literally couldn't touch the concrete? Were they going to wet set the anchors?

Ultimately it's an uncomfortable spot for an engineer.

Yeah. This is a tough call for the owner especially since he is educated about this and not happy. Of course he could have been there for the placement...

"Hot" is a colloquial term, I guess. It means the concrete mix was at the point of hydration where it is setting rapidly. It is typically warm then but the term has to do with concrete achieving initial set. The anchors are simple mudsill anchors (1/2" and 5/8" j bolts) although now that you mention it they forgot my shear wall and column hold downs too (dang it)...another paragraph in my field report...

 

[Rabbit12]

I've never heard the term hot. That's new to me. If it was set-up so much they couldn't install anchors or strike off the top how in the world did they ever get consolidation. Even if they somehow made the exterior look ok how would you know whether or not there is internal voids.

If this was my basement wall they contractor is replacing this. I'm paying for a quality product. Whether or not it "works" is irrelevant to me. I think it'd be damn hard to guarantee the expected life is equal to a properly constructed wall.

 

[hokie66]

This is rubbish work, and the owner should get what he contracted for. The thing which struck me most is the statement that the concrete was too hard to install anchor bolts. Why weren't they in place before the placement? The GC is incompetent.