Bad bad honeycombing

[DKMarty]

This wall was poured with no vibrating. The result is a lot of honeycombing and segregation (In some places we see the original colors of the small rocks used. It's like they never touched cement paste)


The wall is 7inch thick with a good deal of rebar in it. It is a wall inside the house, so no water intrusion worries there. The wall must carry a first floor deck, appr 3 tonnes per meter wall.


Some of the honeycombing has been chipped off as seen in the pics. It comes off quite easily with a hammer. Some places it can be chipped off almost through the entire wall. Other places It's more superficial.


What do you guys think? Should the entire wall be demolished and redone?

IMAGES

https://imgur.com/a/h60m7QN

 

[jayrod12]

Yes. Remove and replace.

 

[DKMarty]

Remove and replace entire wall? Or just honeycombed areas?

 

[Ron247]

I would replace the entire wall. You have no real idea how much honeycomb is just below the "smooth" visual surfaces or at the center of the wall. The rebar is useless without a sound bond of the rebar to the concrete. I assume if there is a "good deal" of rebar in it, the rebar must be needed to resist the loads.

 

[hokie66]

It is a lightly loaded interior wall, so I imagine that the honeycombed areas can be repaired. But I would want to investigate whether or not this poor level of quality has extended into more elements of the structure.

 

[Ron]

Agree with hokie66. This becomes a very deep beam, but you need to do a little investigation. Core the wall in an area of honeycomb to see if it is full section. If so, you probably will need to remove and replace. Epoxy injection can help, but that's usually reserved for smaller areas. This is indicative of poor quality control by the contractor.....thus be wary of other locations.

If core shows integral consolidation, then repair the honeycomb areas with an appropriate repair mortar (SIKA has several good ones...other manufacturers as well.)

 

[MIStructE_IRE]

That’s about as bad as it gets... If in doubt, whip it out!

In reality you have no real way of quantifying this. It might be OK, but who knows. Put the onus back on the contractor with your recommendation to remove.

 

[oldestguy]

I'd chip out and replace with stiff cement grout. Then the deck should have re-bars BOTH WAYS. Thus the weak areas will be bypassed to better areas that can take the load.

 

[TehMightyEngineer]

Yikes. I've had a wall that was almost as bad but it was due to a mix that was shipped too far and dried out. We had lots of honeycombing and pour line cold joints, but they were discretely located and we found a way to patch it. Involving coring the wall to prove that there were no internal voids and lots of work to ensure it was sufficient even with the defects. Not fun and not something I'd recommend.

This is way worse; definitely demolish and replace.

Ian Riley, PE, SE
Professional Engineer (ME, NH, VT, CT, MA, FL) Structural Engineer (IL, HI)

 

[Ron]

The testing, which should be at the cost of the contractor, might be more costly than the fix. Ultrasonic testing, coupled with cores, would find internal voids, but must be done on a tight grid...thus expensive. UT could not be done on the exposed honeycomb...just the potential hidden voids. Have done this numerous times, to salvage existing construction.....not always possible, but an option.

 

[epoxybot]

Epoxy Injection of Honey Combing is one one of the more iffy applications of epoxy injection repair. Most neat (unfilled) epoxy resins for epoxy injection are not meant to be used in a large mass, as they will generate a great deal of heat and subsequent stress upon cooling.

The cement in honey combed concrete can form glass-like bubbles (once filled with water) that create lenses that block the epoxy from penetrating the honey comb. This is not an application where surface mounted ports alone, can address the problem. One has to drill into the honey comb and create a reservoir, through the section, from which the epoxy can radiate into multiple cavities. It is really one of the more subjective epoxy injection techniques and requires patience and exploration. This means an epoxy mix head can sit on a port for some time while the epoxy slowly migrates into the recesses. The longer it sits, the thicker the epoxy gets.

The required epoxy needs a long "GEL TIME". Gel time, for an Injection Epoxy, occurs when one can perceive a slight thickening of the, still fluid, mixed epoxy. Gel Time occurs before "Potlife". Potlife being the time most commonly refereed to in Manufactures Tech Data Sheets. While Gel Time & Potlife are not the same thing, not all manufacturers properly use these terms. Note: Some may disagree with this definition of Gel Time. The ASTM D2471 method for Gel Time uses the word "solidification" which to my thinking is more akin to potlife. A mixed epoxy transitions from fluid, to thickened fluid, to fluid with boogers, to a rubbery hard "solidified" mass in a fluid. The method requires better qualification.

Sometimes an epoxy transitions so quickly through gel time to potlife that there is no determinable difference. At least when using a simple bench top method of probing the specimen with a tongue depressor. A Viscometer would given a more accurate reading but usually isn't necessary.

Your typical Injection Epoxy has a Gel time of between 10 & 15 minutes. Imagine a mix head sitting on a port that slowly pumps epoxy into a void. If the Technicians doesn't stop and occasionally clear the mixed material from the end of the mix head (waste), then gelled material will eventually adulterate the static mixer and then pump, unmixed or off ratio material. You would also be able to feel the heat build in the mix head. Likewise the inject port itself, may eventually need to be abandoned for the same reason.

A standard Injection Epoxy, in a relatively small mass can get really hot. For instance the samples used for Heat Deflection Temperature testing and Compressive Strength testing are about 3/8" x 3/8" in cross section, usually cast in 6" lengths and have to be cooled during gellation in a water bath, to keep the exotherm from rising and causing gas bubbles to form in the sample, from exothermic decomposition.

There are probably only two reasons to epoxy inject honey comb. (1) You are satisfied with the ability of the overall section to perform as intended and injecting spot locations of honeycomb is intended to encapsulate the rebar an possibly restore some section. Or (2) it is a large pour with an special embed that would result in a considerable cost & delay. In the latter, it will still cost a considerable sum, with testing and field inspection & possible follow up injection at additional locations. You will be satisfied to just recoup the time.

The Adhesive Engineering Company used to produce a long potlife, low exotherm epoxy, Concresive 1077 Type II that was intended for these applications. It became Master Builders SCB Concresive 1370. I don't think Master Builders still produces the material, as its uses were very specialized. An Equivalent can be procured from Chemco Systems. Such a material requires a minimum constant temperature of 50F in order to cure, or it will get stuck in a "B" stage of cure. Perhaps SIKA has something like it. Not everything a manufacturer produces can be found in a catalog or online.

 

[dauwerda]

This makes me wonder how many residential concrete walls poured with ICF's actually look like this (or worse) and no one knows about it because the forms are left in place to hide it all.

 

[DKMarty]

Thanks for all the replies. The concrete supplier sent a specialist to look at it and he deemed the wall as "certainly usable" for the purpose it's intended to fulfill.

The rationalization for this was
A a rebound hammer test shows the wall as absolutely fine
B The honeycombed areas do not chip off that easily. It takes the backside of a hammer or some other sharp object to get the stones out.

He advised us not to chip off anymore honeycombing. Just to coat it with some special two-component mortar in two layers with the same product.. First coating should be mixed to a thin solution, second to a thicker solution.

 

[racookpe1978]

No. Don't do it.

Yes, that "specialist" is covering nicely for the supplier.

But the good news is ...... It will be very easy to demolish the wall. A few swings with a sledgehammer, and "Gee, it fell over last night."

There is no load on top of the beam/wall, so less rework in the rest of the house to replace it because yo don't have to prop up an upper floor.

 

[hokie66]

It's an interior wall in a house. Compare that to an interior stud bearing wall. The concrete wall, as bad as it is, will be much stronger than the stud wall. So if it were my house, it would not be coming down. Repair and move on.

 

[MIStructE_IRE]

I was thinking that too hokie, but he does mention that there’s a great deal of rebar in it.

DKMarty - what kind of loading have you got here? Why so much rebar for a house wall?

 

[DKMarty]

The wall must carry a first floor concrete deck. That's about 3 tonnes per meter wall. The amount of rebar is two lenghts of no3 for every course, which is 30cm. Above door openings this is doubled.

The system is an ICF which uses ply-form on one side instead of EPS. The forms can be reused and can be used on both sides of the form, to create a raw concrete wall. The plastic ties are set every 30 cm and they have two cavities for rebar placement.. We simply used both cavities, just in case.