Wall Honeycomb | Investigation and Repair
Wall Honeycomb | Investigation and Repair
(OP)
I know this comes up here a lot and it ends up largely being a judgement call but - see attached photo. This is a basement wall, inside face. The rest of the wall so far is fine. This is the lower 1/2 of what will be a two story wall (i.e. this is subbasement to basement, upper 1/2 still to come). There are pretty distinct lines at each placement lift, looks like no one got in there with a vibrator.
The back face is stayform so I can't and won't be able to see it. I am thinking that I will ask them to core the wall in a few of the bad areas to see the inside of the wall.
- The top and bottom of wall are decent so it seems that rebar bond should be ok and shear ok. If the inside looks good then it's just a chip/clean and repair mortar fix?
- If the inside doesn't look good.... repair options (other than demo)?
The back face is stayform so I can't and won't be able to see it. I am thinking that I will ask them to core the wall in a few of the bad areas to see the inside of the wall.
- The top and bottom of wall are decent so it seems that rebar bond should be ok and shear ok. If the inside looks good then it's just a chip/clean and repair mortar fix?
- If the inside doesn't look good.... repair options (other than demo)?






RE: Wall Honeycomb | Investigation and Repair
RE: Wall Honeycomb | Investigation and Repair
If it's just this one wall area I would highly suspect it's cheaper to demolish and replace than to repair. I went though a similar job with a basement foundation that was almost as bad (except it was the entire wall) but the site was remote so demoing and replacement of the concrete was extremely expensive, so we went with a repair.
My steps involved: calculations to prove the wall works structurally, coring and testing, chipping and grinding the repair areas, cleaning, bonding primer, SikaTop 123 PLUS repair mortar, heated enclosure (cold weather curing), carlisle wrap below grade (for durability concerns), backfill, waterproofing coating above grade (my project was a sand/salt storage shed so above grade durability and chloride resistance was paramount), reports and documentation throughout.
Easily cheaper and easier to demo and replace.
Professional and Structural Engineer (ME, NH)
American Concrete Industries
www.americanconcrete.com
RE: Wall Honeycomb | Investigation and Repair
RE: Wall Honeycomb | Investigation and Repair
You mentioned that the back face is StayForm - which means this was a one-sided forming condition. I can understand why you got this result - using a stiff mix and fear of vibrating the concrete and loosing much of the paste through the StayForm. Or worse, loosing the formwork. I suspect the crew was overly cautious.
Water-tightness may be a major concern, and is always a challenge with one-sided conditions. The final course of action will depend on what is required of the foundation wall. If it is required to be reasonably water-tight, then I would opt for full replacement. If not, then structural integrity will govern, and the previous recommendations are appropriate.
Ralph
Structures Consulting
Northeast USA
RE: Wall Honeycomb | Investigation and Repair
Demo will not be an easy sell, they have several hundred linear feet of wall to go + the 2nd level of basement wall and then 20+ story superstructure - and of course they are pushing schedule. If it needs to come out it needs to come out but I'm hoping that's not necessary.
In the interest of showing this works does any of the following sound incorrect:
- I agree that there is a horizontal joint, I'll get coring here to verify that it goes all the way through. However, I am guessing that I can show that this joint works for strength pretty easily - mostly a shear issue and they are near midspan at a basement wall so likely a big cushion there. Any other issue with the joint?
- Durability: Outside face - I'm way above a water table, walls have insulation, w.p., drainage board and there is effectively zero soil here - these are lot line sites so 2" away is someone else's basement wall. Inside face we can repair/protect.
TME - to check strength did you use cores/breaks and redo your calcs based on these numbers? The 123 specifies max. of 1.5" lifts, is this how you did it? Seems like that will take forever. I was looking at the 111 which can be formed/poured in larger lifts.
They are going to keep going, no stopping them - so I'm thinking that worst case scenario we build a 'liner' wall later on in front of this one.
RE: Wall Honeycomb | Investigation and Repair
We took cores and verified that the reduced compressive strength didn't change the calculations. We had a large thrust load on our wall from an arched roof so you'll likely have less strength requirements than we did (though you have a bigger building it sounds like). We assumed that the visibly acceptable areas of the wall had strength equal to the cylinders cast at time of the pour (which tested at the nominal design strength). We also found that the cold joints in our wall were entirely unbonded all the way through, and yours looks worse than ours. You'll want to verify that you can transfer the shear you need across this joint using shear friction assuming a cold joint.
SikaTop 123 PLUS is a good product. We ground the edges of the repair areas down 1/4 inch to give us the minimum thickness allowed (1/8" for SikaTop 123). In our deeper areas we filled them fully as they were typically only 1.5" deep. We did not demolish any concrete so essentially we used the SikaTop as a repair topping over the honeycombed concrete.
If you want to demolish large areas and repour then definitely something else is the way to go.
Professional and Structural Engineer (ME, NH)
American Concrete Industries
www.americanconcrete.com
RE: Wall Honeycomb | Investigation and Repair
RE: Wall Honeycomb | Investigation and Repair
Professional and Structural Engineer (ME, NH)
American Concrete Industries
www.americanconcrete.com
RE: Wall Honeycomb | Investigation and Repair
RE: Wall Honeycomb | Investigation and Repair
RE: Wall Honeycomb | Investigation and Repair
Professional and Structural Engineer (ME, NH)
American Concrete Industries
www.americanconcrete.com
RE: Wall Honeycomb | Investigation and Repair
RE: Wall Honeycomb | Investigation and Repair
RE: Wall Honeycomb | Investigation and Repair
How to detail the new wall section to the existing footing. Should they sawcut close to base, then hand demo the remaining leaving that remaining several inches of wall dowels intact which can then receive couplers to the new wall vert bars?
RE: Wall Honeycomb | Investigation and Repair
Hopefully the footing is in much better condition.
Given the condition of the wall, it should not be too difficult to chip/hammer out, preserving all of the wall dowels coming out of the footing.
Ralph
Structures Consulting
Northeast USA