Help with spall on new concrete

[shedkept]

I am new here but have lurked and learned.

I am building a new barn/pole shed. The concrete was poured last Thursday and the concrete finisher made his cuts with a Sofcut saw the same day.
The next day they applied a water based sealer/curing agent.

After it dried I noted spalling at the edges of these joints and upon further investigation was able to "pop" up dime to quarter size pieces from the concrete at just about any point in the building. They were easy to find as they had a grayish color to them since the sealer wasn't able to work it's way all the way to the substrate.

Opinions have varied from the concrete being sloppy to the finisher working it too soon or too long. The final finish was burned smooth as glass.

An engineer friend in the large consruction business looked at it and thought that while the floor was probably ok (without doing a cylinder/core test) the fix was one of 3 solutions.

1st was to cut wider joints and use a filler/seal in them. This was "ruled out" since we figure it's going to spall no matter how good the cut.
2nd choice was to grind down the surface to a good substrate and apply a new concrete topping like Ardex.
3rd choice was to tear it out and start over. This one is the most work intensive as the building is 36x64 with about 6-7 inches of concrete throughout. This is the least appealing as all of the aprons and approaches have been poured and finished.
4th option got thrown out last night which is hugely labor intensive (although not as bad as tearing out the current concrete). The GC suggested grinding down to the substrate and applying 2-3 inches of fiberglass infused concrete after a bonding agent was applied. The extra work would come from having to raise all the finished aprons by 2-3 inches as well.

I am in the drivers seat as this isn't going to cost me anything but time and frustration. I really wanted the building buttoned up by mid-June but am willing to exercise some patience to get the final product up to the level of the rest of the structure which is going to be really nice.

I appreciate all opinions and welcome your thoughts.

Tom

 

[shedkept]

Well; that was easy.

The GC is going to remove it all and do it again. No charge.

You guys can go back to sleep now.

 

[Ruddy]

ZZZZZZZZZZzzzzzzzzzzzzzz

;-)

 

[shedkept]

Funny.

We're having a structural engineering firm formulate the next job and we are using a different concrete finishing contractor. That ought to do it.
It might seem to be over-kill but as an architect buddy told me long before I got started; "Make damn sure whoever is doing the concrete knows what he is doing because you will have to live with it for a long time."
Boy, was he ever right.

We'll slump test every load this time.

And, if I see another vibratory screed machine I'm going to shoot it.


Tom

 

[1969]

What will it cost the concrete contractor to replace this ? Unless you are quite gentle with any floor of this nature , you will get scars etc regardless. You might want to see if he will do some kind of a $$$ deal to leave as is. BUT, if your not happy and want it redone, thats exactly what you should do. JMHO, Best of luck.

 

[shedkept]

I'm not sure what it is going to cost but he's taking care of it. We have a pretty tight community and the folks that did the initial grade are going to do it. I'm going to get them to do some other work while they are there which works out really well for everyone.

Since the entire pad including re-bar and whatever comes with it is being removed the only scarring will be what the skid-steer with the jack hammer is going to make to the old concrete and all of that is coming out. That's all going to the land-fill.

I'd wrestle over money but it's more a matter of something I have to live with. If you screw up nailing a board you can remove it and try again. Concrete is forever.

Thanks!

Tom

 

[pauls340]

I know this is after the fact, but your fix could have been very cheap and quick...Mg-Krete is a fast cure concrete repair product sold thru construction supply companies (www.imcotechnologies.com) all over north America. It is without a doubt, the best spall repair material available. We have used it on thousands of spalls from 1/16" to 17" deep pours at the airport...any temperature, any depth. We skimcoat complete two car garages in 2.5 hrs and you can park on it that night. After it offgases, you can paint it or epoxy it. Impervious both positive and negative to water, gas, oil, jet fuel, trans fluid and even pickeling juice. AND, it gets to over 11,000 psi ! Good luck.

 

[shedkept]

That good information, however, the contractor decided to do the removal without further consideration to spall repair.
To do it right would have required that the slab be ground down to the point where there was a hard substrate. A lot of work.
ARDEX or similar would have been used which isn't exactly cheap either.

During the demolition it was noted that the surface would "fly off" once the hammer began hitting it. It came off in sections as large as 8-10 inches and showed every sign of being improperly finished. (too soon, too wet, vibratory screed). I saved sections of these pieces because they were anywhere from 3/16's to 3/8's thick. That is too much "cream". Otherwise the concrete appeared to have set up well.

An engineer friend has let me read the ACI Guide to Design of Slabs-on- Ground. Quite a lot of good information for the layman but even more so for those with advanced degrees in engineering and physics. (I'm not in that category)

 

[twostory]

Why is a "vibratory screed" a bad thing?

I monitored my slab pour, the finisher went over the "just poured" concrete once (maybe twice) with the vibratory screed to level it out and let the concrete bleed off the water. He then hand & power troweled and lightly brushed.

I can not see how a vibratory screed that is not used "over and over" again would cause too much cream to get to the surface.

 

[shedkept]

He worked it too wet with the vibratory screed. It causes the gravel to fall out of suspension and you end up with mostly sand and things that don't take much abuse. In my situation it was a lot of sand. It took NO abuse.
I cannot say for sure but the one architect I trust likes to see judicious use of these things. Used too much and they create more problems than they solve.

Up until I built this garage I had never seen one used. All I ever had ever seen were "real men" working the old fashioned screeds. All big men with broad shoulders and a hard work ethic.

Kiss that goodbye.

Tom

 

[Rick3Foxes]

Seems to be more and more common.

Good men being replaced by vibrating gadgets...

 

[twostory]

He worked it too wet with the vibratory screed. It causes the gravel to fall out of suspension and you end up with mostly sand and things that don't take much abuse. In my situation it was a lot of sand. It took NO abuse.

The concrete had too much water in it, if the vib. screed caused that much settlement. The concrete guy /or/ the concrete truck driver are to blame here. The concrete was delivered too wet, or the concrete guy had too much water added after the truck arrived.

 

[kartracer23]

I've got a question on spalling. I've got maybe a dozen or so on my front porch (extremely smooth finish). It's from ice melt I used this year (not sure what was in this stuff, but I've never had the concrete act like that before with ice melt). They're quarter size or so - and probably 1/16-1/8 of an inch deep. Is there anything I can use to fill these - and fill just the spalls without making a mess of the surrounding area? Since it's right where you step onto the porch (hence the ice melt in the area) I'd like it to look as nice as possible. The things I've used in the past to fix spalls were always a mess and although they sealed the spalling, the appearance was the same - if not worse. I guess i'm thinking of a more precision way to do it?

 

[shedkept]

The new pour happened Friday May 21st. It went down without any issues.
On this job the GC hired a fellow who was very experienced. His repetoire included linear accelerators and the like.
His crew numbered around 9-10 and one of the heads of the concrete company even showed up as well. We used a different outfit as the 1st bunch didn't meet his standards. As he put it; "with the volume we do they are always preaching price". He said: "It's not always about price". Truer words never spoken.
He requested NO ADDITIONAL WATER to the mix. Plasticizer was used and they did what I expected to see after getting it all in. They walked away and let it "do its thing". The "boss" watched it like a hawk. When it was time they worked it and stopped. Only when he was satisfied that it could be finished did they start up. The entire time the finishers worked the outside edges.
They also had the widest bull float I'd seen in a long time. The floor is many times flatter. No undulations or wavy areas. The use of a laser level was pretty neat to watch as well.

In the end it took all day and they didn't pull off until it was nearly 9 hours after the last truck left. The Soff Cut saw did its thing and there was little to no pulling up. Of course, this was a Peterbilt compared to the 1st guy's version which looked like a VW Bug. The operator was a very patient person too which I feel has a big effect on the final product. Let the saw do the work.

Now, we move on to more important things like "finishing the building"!