Concrete slab issues? Need opinions

[DavesGarage]

Alright, update for today. Crew showed up this morning and immediately went to digging under the slab. Foreman was here for about 20 minutes and instructed his guys then bailed out. They dug a nice footer out until they hit firm ground under the opening that was 2 feet front to back (1 foot of it was under the existing pad), used a jumping jack to pack the soil in the footing, installed a couple vertical rebar and a couple horizontal rebar while drilling and using epoxy to set them into the giant footings for the simpson walls. The new footer was about 2 feet front to back, 6 feet wide (spanned between the existing large footers) and 2 feet deep top to bottom. They used the ******** to work the concrete up under the pad and set the forms about 3 to 4 inches above the bottom of the pad. I am happy with the fix but then again, I am not dealing with concrete or structure very often. I did notice after it was done that they didnt tape up the vertical rebar like the others. Satisfactory?

 

[DavesGarage]

Forgot to mention, for this footer they ordered 1 yard of the same mix that the pad was (3500 psi and stealth fiber). They cut it really close, I would have like to see it come up higher but again this is not my forte.

 

[wssix99]

Did they pin the slab pieces to this new footer or did they just connect the two footers together?

 

[readhead]

I would have liked to see some non shrink grout between the new work and the slab. Considering where it is and the thickness of the slab you will probably be fine. At least the guy made an effort to make it right.

 

[Todd.Brock]

I'm not a concrete guy, but if I didn't have the GJ for feedback, I would look at that as a solid effort to make it right.

 

[DavesGarage]

WSSIX99, they did not pin the slab, just installed pins and rebar into the footings. I didnt think it would be all that necessary to pin the slab since it was monolithic, 6-8" thick and had rebar/ stealthfiber but I can see where these is the chance for movement between the 2 pieces. That probably could be avoided (as readhead mentioned) by using a mix that doesnt shrink. Pray for my sanity! I dont plan to drive dumptrucks over this but I do have a diesel Excursion (close?). This is also underneath where the trucks will park so a minor crack wont send me over the edge, if it was where I will be rolling tools around I would be beside myself. Hopefully the crack wont go past the 8 foot saw cuts!

 

[wssix99]

Hopefully the crack wont go past the 8 foot saw cuts!

It won't. The repair that was done will stop it at some point. (You've completed that "barrel ring" around the slab to help hold every thing together so that any cracking should go back to the control cuts, where they belong.) The crack could grow a small bit more. Pinning would have stopped it completely, but there's nothing to worry about structurally.


The slab is only as strong as the foundation beneath it. Physically:

6-8" thick

In the way you've designed your slab, this thickness reduces/spreads out the pressure on the foundation from the vehicles traveling over it. The effect of this is exponential with the depth, so this is really over-designed. (You could probably put this slab on quicksand and be fine for what you are doing!)

rebar/ stealthfiber

This doesn't do anything for you structurally except help control shrinkage cracking and keep the slab together if it does crack.

(Some industrial slabs do use structural rebar, but you have to get bars in a few inches apart before you start seeing that kind of effect.)

 

[DavesGarage]

Thanks for all the help and info guys! It rained pretty good the last few days so i will keep an eye out for any more issues.

What do you guys suggest for using in the saw cuts? I shop vac'd them out later the same day that they were cut but its been raining quite a bit so Im sure cut dust has fallen back into the cuts. Should I clean them out again and then use silicone to fill in the cracks?

 

[readhead]

Sikaflex makes a product that most of the pros use. I have seen it at HD or you can get it at a concrete supply.

 

[wssix99]

use silicone to fill in the cracks?

Definitely not!

Sikaflex makes a product that most of the pros use. I have seen it at HD or you can get it at a concrete supply.

^ This stuff is great if you are going to leave the floor bare and untreated.


Are you going to coat the floor with anything?

 

[DavesGarage]

I would like to coat the floor some day but probably wont happen. There are two kinds of sikaflex if I remember right, one is self leveling. That the one? seems like it would just fall into the crack and fill it up, that would take a truck load of silicone.

 

[wssix99]

I would like to coat the floor some day but probably wont happen. There are two kinds of sikaflex if I remember right, one is self leveling. That the one? seems like it would just fall into the crack and fill it up, that would take a truck load of silicone.

The sikaflex is thick (even though it levels) and it won't flow in to the small cracks.

A non-shrinking, synthetic topping product will fill your cut joints perfectly if you are going to coat the floor with epoxy, etc. later. https://www.ardex.com/product/toppings-concrete-restoration/ < I have a flake floor and used this in my cut joints. They are completely invisible!

 

[Fatboy148]

This may be a silly question but I didn't see where anyone else has asked....

Did your architect / engineer / design professional spec out an under slab vapor barrier? If so, I didn't see it in the picture that showed the rebar starting to get laid out. Either way... IF... you ever consider covering the floor with a product that doesn't "breath", you need to be aware of possible issues.

IF he did have it detailed in his plans, your concrete contractor has a issue that will be real tough (impossible) to fix.

 

[DavesGarage]

Fatboy, no he didnt have the vapor barrier in the plans. I did ask about it though and the response from the engineer and the concrete guys was "In Arizona??". I wasnt aware that coating a slab would be effected by a vapor barrier, I will keep that in mind!

Thanks again for the info wssix99, I will pick some of that sikaflex up next time Im at the hardware store. Its unreal how many delays have happened from the lumber company. The framers are going to be starting in a week because the lumber guys have dropped the ball!