Rain Damage at Top of Augured CIP Pile. 10

[KootK]

PARAMETERS

- Helping out with a field issue on someone else's design.

- Augured CIP piers for a pickleball screen wall fence thing. Seriously. Part solid, part chain link.

- Contractor allowed heavy rain to fall on the tops of the piers 60 min after casting.

- Ridiculously windy location. It's small scale but not as small as you might think.

- The owner is a municipality and they are traditionally quite concerned about durability.

- The posts supported on the CIP piers cannot be relocated without causing great pain.

- While I can think of several structurally acceptable solutions, I don't want to get too ridiculous with a damn pickleball fence. I'm a traditional tennis guy and generally annoyed by the pickleball striping on my local courts. Why can't the elderly just play Canasta like they used to?

QUESTION: What's to be done?

SOLUTIONS I'VE CONSIDERED

1) Current favorite. Chip the piers down to the bottom of the anchor bolts. Fill the hole back up with concrete and call it good. This probably does not rigorously deal with durability or anchorage but kind of feels "reasonable" to me.

2) Pull the piles out vertically somehow, augur bigger holes at the same location, and put the piles back. Expensive.

3) Install new piers located away from the posts and install a grade beam ring on the piers such that the superstructure posts can stay where they have to. Expensive. This does kind of feel like an excellent mechanical solution to me however.

4) Excavate the piles and come back with some kind of retaining structure:

a) Sonotube in engineered fill.

b) Sonotube on footing.

c) Retaining wall.

All crazy expensive.

 

[JAE]

So the rain didn't start until 60 minutes after casting? Or started right after casting for 60 minutes?

Can you see if the top layers of concrete are truly damaged or just the top 1/4" or so? If the latter I'm not sure I'd do much of anything...maybe chip out 1/2" and put back some non-shrink grout to seal the top.

I'm surprised by the anchors. Usually tennis posts are simply embedded in the piers (at least the ones I've seen due to the large lateral force imposed at the top of the posts by the tension in the net).

 

[Aesur]

I'm a fan of chipping away the concrete to bottom of anchors, roughening surface, using a bonding agent, cleaning rebar and pouring new concrete. If the anchors are still an issue, get longer anchors and chip a bit further to lap the bars and anchors and done.

 

[KootK]

So the rain didn't start until 60 minutes after casting? Or started right after casting for 60 minutes?

The former, according to the reporting of the contractor. Are you thinking that 60 min old concrete is probably pretty good?

Can you see if the top layers of concrete are truly damaged or just the top 1/4" or so?

How do I ascertain that? I pitched the same solution that you recommended internally, maybe via hydro demolition of the soft stuff etc. Colleagues expressed concern that the rain probably penetrated some distance through the soil around the pile, possibly messing with the concrete lower down. I found that moderately convincing.

I'm surprised by the anchors. Usually tennis posts are simply embedded in the piers (at least the ones I've seen due to the large lateral force imposed at the top of the posts by the tension in the net).

Ditto. But, alas, we are where we are. Junior folks that grew up with APP D seem to be quite skeptical of other, more traditional anchorage solutions. And that makes sense.

Thanks for your help. It's good to have my favorite cyber mentor watching the store, particularly on the "reasonableness" front (never my strong suit).

 

[WinelandV]

Based on the anchorage depth and the vertical r/f, I like option #1. Not enough anchor length to lap the anchors to the vertical r/f, and there's no way you're developing the vertical bars above the anchor breakout cone - i.e. the loads are small. Maybe take the pier down another 150mm below the anchors depending on how you feel about the load path and r/f development.

Please note that is a "v" (as in Violin) not a "y".

 

[KootK]

Not enough anchor length to lap the anchors to the vertical r/f, and there's no way you're developing the vertical bars above the anchor breakout cone - i.e. the loads are small

I see it the same. Thanks for your input.

 

[cvg]

i would start with testing the surface

"sounding" using a hammer is a typical field method to test if concrete is hard/durable/delaminated/cracked/soft

listen for a ringing sound, not a thud

i would not worry about rain penetrating the soil along the sides. that would be unlikely to cause any issues

the following may also be useful:

Engineer Manual 1110-2-2002 EVALUATION AND REPAIR OF CONCRETE STRUCTURES
Link

 

[Enable]

I don't buy reduced durability for concrete lower down as it couldn't exactly mix with the concrete and if anything, provided a better cure than usual. Worst case is the first few mm are weak but that's unimportant with 3" of cover.

If you need something quick just to get it out and moving then I am also partial to your option #1. I'd probably add some additional dowels epoxied into the base. Mostly because they're cheap, you're already there, and why not (can sell as beefing up the durability).

If this is actually of some size (you say not as small as we might think) then I might explore the testing route. Core the top surface and put under a microscope to see extent of scaling / mixing. Then load test a welded fence post to the in-situ condition, if it passes then call it good. This still all costs money but maybe under $5k and if we're talking about tons and tons of courts that require chipping / new concrete / etc then maybe they might want to go this route. It has a high probability of justifying doing pretty much nothing IMHO.

 

[dik]

I think your #1 is the correct approach. Is there a need to remove all concrete? I would have thought the top couple of inches would be adequate.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[KootK]

Is there a need to remove all concrete? I would have thought the top couple of inches would be adequate.

There is not. It's just a matter of establishing how much removal is enough. Perhaps you are right about the top couple of inches. Thanks, as always, for coming to the aid of a damsel in distress.

 

[KootK]

If you need something quick just to get it out and moving then I am also partial to your option #1. I'd probably add some additional dowels epoxied into the base. Mostly because they're cheap, you're already there, and why not (can sell as beefing up the durability).

Sold. I'm pitching that now. That said, other solutions are still valuable here as it's difficult to anticipate the pushback that we'll get on this one.

 

[KootK]

I'm surprised by the anchors. Usually tennis posts are simply embedded in the piers (at least the ones I've seen due to the large lateral force imposed at the top of the posts by the tension in the net).

no one likes to embed fence posts anymore because replacement maintenance issues, they want a clean weld to an embedded connection so they can replace the posts easily when damaged

I passed your inquiry along and that was the response.

 

[JAE]

I don't buy reduced durability for concrete lower down as it couldn't exactly mix with the concrete and if anything, provided a better cure than usual.

That's my thought as well.

Also - if the rain didn't start for 60 minutes after placement - then I just wonder how much concrete was really affected by the rain - although your photo looks like the concrete certainly was affected (that smooth buttery look).

Here's what I might consider:
1. Per cvg - sound out the top - try to determine how much of the top was "damaged". (the concern is a too high water cement ratio right?)
2. Verify if the distance to "good" concrete, or at least acceptable concrete, is small such that you still have adequate anchor embedment in "good" concrete.
3. If embedment is OK if you remove/replace the top X" of concrete then proceed with step 4.
4. Remove/chip away (carefully!) - perhaps grinding vs. chip hammer - the top poor concrete - leave a roughened surface and patch with a non-shrink, non-metallic grout - or a modifed polymer patching mortar.
5. Install your base plate and post.

The above items 1 and 2 are a quick, rough, not-exactly-perfect way to attempt an evaluation of the rain damage. You could take a core and have a lab slice and dice it down its length and via petrographic analysis determine the w/c ratio variations vertically - but that's just me living in a dream world where money doesn't matter.

If you find that the concrete is crap for 2 to 4 inches, then maybe a total removal and re-do on the piers is the least expensive option (vs. chipping down to bottom of anchors - contractors aren't surgeons).

 

[JAE]

I like enable's idea too - but in my part of the world - high w/c ratio concrete exposed to freezing is a bad thing - will look like crap in a few years.

(note: "Crap" is a technical term only used by highly trained professionals who like to look cool around tough contractor dudes)

 

[Craig_H]

Have you tried popping off a base plate yet? I am genuinely curious how much of the rain water whicked under the base plate, and how much that plate acted as an umbrella.

PS: I hope Civil's need for those dowel holes disappeared?

 

[dik]

"Perhaps you are right about the top couple of inches."

I've encountered some pretty damaged concrete from rain, and it is seldom damaged beyond an inch or so.

"Thanks, as always, for coming to the aid of a damsel in distress.""

nudge, nudge, wink, wink...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[GC_Hopi]

Definitely removing the base plate and a quick inspection with some sounding is the way to go. I would not expect any real damage to the concrete but if it is looking/sounding ugly them chip back and use some non shrink grout. I have had some slabs been caught out in the rain in Florida and generally if the concrete has had time to set and get a initial float to seal it up then it works out ok. Obviously the proof is in the final product particularly the aesthetics when dealing with floor slabs.

 

[jerseyshore]

I feel like 90% of contractors I know wouldn't even blink at something like this or bring it to anyone's intention. You would get the "this thing could support the Freedom Tower" comment. Around here, if the house is on the bay side these guys are just hoping their footing inspections take place during low tide.

This is a pickleball fence, I probably wouldn't do anything except maybe drill 4 new extra long anchor bolts. Would also poke around to make sure it's not mush right underneath and then kick my boot and say "this thing ain't going anywhere".

 

[KootK]

I feel like 90% of contractors I know wouldn't even blink at something like this or bring it to anyone's intention.

In all seriousness, I wish that this had not been brought to my attention. But... it was. And now I have to do something "responsible". It was actually the owner's rep that flagged the concern.

Definitely removing the base plate and a quick inspection with some sounding is the way to go.

I agree. As it turns out, the base plates are not installed. I'm told that what we see in the photo is a plywood setting plate.

Have you tried popping off a base plate yet?

No, but we will have that done. Also, see my previous comment in this post re plywood.

..then I just wonder how much concrete was really affected by the rain - although your photo looks like the concrete certainly was affected (that smooth buttery look).

Agreed. We also need to get the top of the thing washed off I think. Much of what see is just a layer of rain mobilized mud I suspect.

 

[LittleWheels]

I don't think that rain occurring 60 min after pouring will have affected more than the top 30mm or so of concrete (maybe 50mm at worst?), if setting had commenced prior to the rain. A core will let you examine the concrete on the surface and at depth.

Things would be different if the concrete had not reached initial set and there was consequential mobilisation of the fluid concrete which can incorporate additional water into the concrete. Otherwise, puddled water is just improved curing.