I had EXACTLY the same situation when they took the slabs off my pour. Tons of honeycombing...

First I did a lot of on-line research which I'm suspect you've also already done. On-line research suggested that SOME honey-combing is perfectly normal and is due to failure to completely vibrate the air pockets out. If you don't have too much, it is no big deal and you just cover over the honey-combing with a "parge coat." (Some builders refer to applying a parge coat as "underpinning" which isn't the same thing at all but...)

Problem is that I also learned that too much honey-combing CAN be problematic because it CAN indicate an overall poor pour using concrete that had begun setting up while still in the truck. This results in more air pockets being caught within the slab which will be weaker and more prone to cracking than if poured with fresh concrete. Plus, extensive honeycombing can expose the rebar within your slab to moisture so that it can rust which will also reduce the strength of your slab.

Nowhere could I find anything helpful on how to tell whether the amount of honeycombing I had was normal or excessive. (You would think there would be pictures showing "normal honeycombing" and "excessive honeycombing" or some kind of mathematical formula like "if honeycombing covers more than x% of the edge surfaces of the slab, it is excessive. But nothing like that is available.)

So, I had the company that had originally engineered my slab come out and take a look. Biggest waste of $200 I ever spent! The report they provided me told me EXACTLY what I'd already learned (i.e., some honeycombing is normal, too much can cause early foundation failure) and then they basically said, "we can't tell you if the amount of honeycombing you have is extensive enough to result in early failure of the slab. If you are concerned with how it looks, you can make it look fine by putting a parge coat over it." GRRR! I was pissed and wrote them back that their report told me absolutely nothing that I had not learned within 15 minutes of researching on the web and that it was the single most useless "report" I had ever received in my entire life on any subject.

Needless to say, my builder took the engineer's letter as meaning "there is nothing wrong with your slab" which, of course, it NOT what it said.

After throwing my hissy fit with the engineering company, I learned that there are a few companies that actually CAN tell you whether or not the honeycombing extends within your slab and is extensive enough to be problematic. These companies use an instrument that sends sound waves into the slab and then they analyze the echos. I forget what they actually call the process when done on concrete but it operates on exactly the same principle as SONAR does so I think of it as sonaring the concrete slab.

The company I talked to is out in Colorado somewhere and, if you want me to, I'll dig up their address for you. Only trouble was, it cost something like $12,000 to $15,000 to do the testing so, while it gets done on big commercial builds (skyscrapers and warehouses), the company said they'd never been hired to run their tests on a residential foundation and wouldn't recommend spending the money.

Testing isn't going to fix your slab IF you have problems and, even if you don't have extensive honeycombing it is possible to wind up with foundation problems 10 years down the road anyway. And, fixing a residential foundation that fails would likely not cost all that much more than having the test done in the first place.

So, on balance, it just seemed to make more sense to us to not do the test and cross our fingers and hope for the best. I was NOT happy with that decision but what can you do?

Now, 3.5 years after the foundation was poured, we do have foundation problems and are facing a $10K to $18K slab repair bill... and meantime, our sorry a-- builder has filed bankruptcy which means he no longer has to honor the ten-year foundation warranty that the state of Texas mandates that builders provide.

I do wish I had something more positive to share with you. If you want to post some pictures, I might be able to tell you whether your honeycombing is as extensive as what we had or not as bad or about the same.

I can also tell you that, once a proper parge coating is on, the foundation will look fine... unless you start getting cracks in the parge coat which indicate the foundation is cracking.

Good luck

Thanks for the detail Cpate. I spoke to him and he indicated they'll be "underpinning" as you'd indicated.

One other question - for whatever reason on the slab that will be covered by either ceramic tile or carpet they did a brush type finish as opposed to what i thought was the more customary power trowel finish.

Any problem with that down the road? Does that make it harder or easier to replace tile 10 Y from now?

Sorry, don't really know anything about brush-type finish versus power-trowel concrete finish except what they look like tho I always thought that brushed finishes were mostly used on walkways and around swimming pools to provide a bit of traction.

It seems reasonable tho that a brushed finish might ensure that tile bonds a little better because the little grooves would give the mastic (thin-set) used to hold tiles down a little more surface area to cling to. I'm pretty sure that there is more work and expense involved in brush-finishing concrete so I rather doubt any builder would bother to do it without a good reason.

Personally, I think of tile as a "forever surface" and (knock wood) I have no intention of EVER replacing mine. Our concrete was not brush-finished and we have not had any trouble with tiles popping up or anything like that so I'm not sure you really need a brush finish to hold tile down. Still I suppose having the tile's grip the concrete surface be a little stronger is probably generally a good thing. On the other hand, if you're planning on replacing the tile ten years down the road, maybe not. Did you tell your builder that you're thinking you might want to replace the tile ten years down the road?