No need for a vapour barrier under an outside slab that is going to get rained and snowed on top.

 

Saturating the soil with water is much simpler than poly and that's the first thing i learned as a kid when mixing in a wheelbarrow at a temperature around 100F. Those are hard learned lessons that stay with a person for a life time. Poly hadn't been invented then and i still don't use it.


https://www.ascconline.org/Portals/0/docs/POSITION-STATEMENTS/PS-17-free-fall-concrete.pdf




Edit: Edit:

 

Yep, that is the method that I learned a half century ago.

Dampen the ground to prevent any of the mixture from being denied it's needed water to cure.

Then in over 80 degree weather either place a wet blanket, or keep a bit of sprinkle on the slab to prevent scaling.

Heat will dry the outer layers and cure them, but the inner layers are still green, and in a few days to months the scaling happens and ruins the slab.

Be sure that you have undisturbed ground underneath, to prevent any settling, and making the slab unlevel.

That would make the tank draw oddly, and might cause a problem if unlevel enough.


ED

 

If the soil has good drainage, use the poly. Don't let 40¢ worth of plastic stop you from have the best slab you can make.

 

In todays economy, make that $1.00.:devil3:


ED

 

Thabks for all the tips guys, much appreciated. I should also note that the area is a combination of sand with dirt underneath, if this changes anything?

 

They didn't go anywhere. Those a just air bubbles.

 

How old is the house, the soil around a new house can settle, I am sure you have many feet of fill next to the house.

 

The house was built in the mid 70's - 1974 I believe.

 

I am not sure whether this is a non-problem but I have a general question: When concrete is poured or mixed in a fence pole hole or in a form open to the ground below, what prevents the more liquid components from percolating into the ground leaving the more coarse components no longer in the correct ingredient proportions including water content? Wouldn't a poly' sheet underneath help?

 

Not enough to worry about.

 

Concrete does separate like you suspect and percolate the fines into the ground. If you fill the hole with sand does it disappear into the ground below? I don't think so.

 

Dampen the ground, and you will be fine.


ED

 

Thank you

 

Well I think I will have to rip it out and try again not happy with what appears to be scaling on surface of concrete and the sides look like they have holes in them. Not sure if this would be adequate for holding such a heavy thing such as a full oil tank. I had posted another thread regarding this but I can't figure out how to delete it to just keep this one thread active. Image links posted below of finished job.

https://ibb.co/59Wpz1v https://ibb.co/16P7hdS
https://ibb.co/T88FxW7 https://ibb.co/kJNV1L2
https://ibb.co/fXLVnjv

 

Holes in the side are not an issue. Other than looking ugly it should be fine.
Did you mix it yourself or order ready mix truck?

 

mixed myswlf with concrete mixer, 2.5L water per bag of quikrete.

 

I wonder where all the fines went that were in those holes?

 

If the concrete on top os already flaking is this going to be a problem come the winter months in -35 temps?

 

What was the ambient temperature at the time of curing?

Did you keep it damp with a wet blanket or wet cloths during a hot day?

Premature flaking is a sign of an improper curing process, usually a dry hot day, and the surface cured, but the interior was still green, and cured later, and caused damage that is best R&R'ed.


ED