Tilt Up Concrete Repair Using Shotcrete 2

[sponcyv]

I am working on a job currently where chlorides have deteriorated a tilt up panel excessively. Cracks have developed along the reinforcing lines both vertically and horizontally and extend to the reinforcing which is located in the center of the 5.75" thick panel. There is also excessive spalling on the exterior face of the wall. The wall has deflected out of plane roughly 3". The wall supports roof joists which span 32'.

I am looking at several options and one involves shoring the roof and removing the deteriorated concrete from the exterior face and then adding shotcrete to increase the section of the wall. Has anyone ever done something similar?

I am worried about the pressure of the shotcrete and the necessity of shoring the panel while adding shotcrete.

 

[Brad805]

That is what I was guessing, but the focus seems to be putting something over without discussing the issues of new rebar.

 

[larsacious]

I would shore this immediately.

 

[sponcyv]

Water soluble chloride testing was performed on powder samples. The tests do indicate that chlorides were in the mix leading to the likelihood that chloride accelerators were used.

This building is 40 years old and has changed hands multiple times making it very difficult to go after legal recourse.

Yes, the rebar is corroded and is the source of the cracking.

I'm not worried about shoring the roof immediately as many are in this forum however.

I do appreciate everyones input and this forum is really great!

 

[a2mfk]

Not to be pushy- its your call, you've been to the site, all we have seen is a couple of pictures. But with 3" out of plane lateral deflection, and all of the other indications of distress, why wouldn't you shore and brace this panel and the roof?

 

[sponcyv]

I understand where you are coming from and it is the safe thing to do being that I've been to the site and I've seen it and making them shore would cover myself. I also know the wall didn't experience this deflection overnight. In fact, the wall has been standing for 40 years and I have a strong opinion that the deflection was caused by stress in the panel during erection. When tilt wall panels have been tested under combined axial and lateral loads, the deflections before failure have been extremely high (10" and more). That being said, I also understand that the concrete mixes were good and they were tested in a controlled environment. This wall is not carrying much load. It is my strong opinion that this wall will not collapse outside of an extreme event. I try to see things through the owner's eyes and be practical. Just because I've been to the site does not mean the wall is going to fall in the next week before construction begins.

 

[a2mfk]

I had a long drive today and your problem popped into my head. I racked my brain as to why the panel would deflect inward and not outward as you said, based on the roof connection being eccentric and causing a moment that in theory would produce outward panel deflection. I know its only a theoretical discussion. Maybe it was cast poorly with a small concave, or lifted too early or incorrectly?..

That's interesting about that testing, 10" for how tall of a panel? That's amazing. But that is with intact and developed rebar. I would worry with the amount of corrosion you have that your rebar bond to the concrete and your loss of steel section may leave your panel with very little tensile strength.

Steel pipes and jacks are cheap and fast, can I talk you into at least shoring up the steel joists? The panels then only have to support their own weight.

I do a lot of forensics, this one is very interesting. I am saving that pic to my library. Keep us updated with another post and a couple more pics if you want. Most tile panel issues I have dealt with involve construction problems like improper or inadequate bracing, misplaced connections, etc...

 

[csd72]

A prop is cheap insurance.

If this panel fails and falls on someone before you come up with a solution then you may struggle to get a decent job again. Do not succumb to pressure from the client to do otherwise.

You must never forget that you have a legal duty of care.

 

[dhengr]

Sponcyv:
Can I hijack your thread for a moment? I see two people right here that I want to talk to, and then I’ve got bigger fish to fry this evening. How did your Hertz stress problem turn out, let me know, I really am interested in what you finally did.

This tilt-up wall is certainly an interesting problem, and I will follow it to see what you do. Do what’s right and safe; of course you have to be practical and do what’s best for the client, but you shouldn’t stick your neck out a mile to save him a few bucks or put your company in a dangerous position to do that either.

A2mfk:
I believe you and Slick chided me some time back for not posting sketches of my own ideas, when I harp on that so much. That OP was something about proper location of a light single web stiffener, under two heavy lifting lugs, on a light WF; a complicated little lifting beam problem, which I thought was way over detailed. Then you got after me again the other day for not knowing how to post an attachment, and more or less suggested I should go back to 4th grade, or at least get help from there, in a nice way of course. WELL! Look what I think I can do...... we’ll see. Talk about teaching an old dog new tricks.

 

[dhengr]

I was so damn excited to see if the scan would work, that I forgot something I intended to add....
Thanks to you too, BA for some direction, even if you’re older than 10.

MERRY CHRISTMAS to all, and to all a good night.

Dick

 

[a2mfk]

dhengr- You see, I knew you could do it! Nice self portrait!

 

[rscassar]

Would there be a temperature differential between the inside and outside of the building that caused the wall panel to deflect inwards.