Best material to use to level concrete pad

[Sparky4598]

Hello all, I'm wondering what the best thing would be to use to level a concrete pad would be. The last concrete truck was 1 yard short and instead of calling and making them send another truck to finish the pad to proper thickness I stupidly said I would fix it later.

The pad is 105 inches square and the thickness needed to bring up to level varies between 1 inch and 1/4 inch.

I was thinking of using nonshrink construction grout and the sika latex bonding agent to pour a thin layer.

The pad is just a foundation for a hot tub and the concrete underneath is 5" thick with #4 rebar on 12" grid.

Cost and cracking/delamination of the thin layer is the primary concern.

Any other suggestions or recommendations?

 

[BridgeSmith]

For a sidewalk overlay of 1/4" to 2", I used the bagged sand topping mix concrete. It worked really well for me. I recommend saturated surface dry condition for the existing concrete when you pour the topping. That means the existing concrete is saturated with water, but all free water is blown off (no puddles).

 

[dik]

Can you use Sika top or something like that. Check with the manufacturer's rep to see if applicable.

I don't usually saturate the existing concrete first. The unsaturated concrete 'draws in' the topping for better bond.

Just my experience...

 

[BridgeSmith]

I don't usually saturate the existing concrete first. The unsaturated concrete 'draws in' the topping for better bond.

Our research indicates that dry cured concrete sucks the moisture out of the freshly-poured concrete, causing the cement at the interface to not cure properly. The SSD condition is what our construction spec book requires for all new concrete cast against cured concrete.

 

[dik]

The research I've encountered shows that the moisture/paste 'sucked in' improves the bond. I'll have to look at this again just to be sure.

 

[jhnblgr]

Make sure the product meets the minimum and maximum thickness requirements. Roughen and clean the surface free of dust. A damp surface is typically best for bonding or a bonding agent.

LevelFlor® Datasheet | CTS Cement

www.ctscement.com

 

[XR250]

That entire slab is only 1.25 yards. How were you a yard short?

 

[BridgeSmith]

That entire slab is only 1.25 yards. How were you a yard short?

Oh, you're right. Yeah, something's off with the size description of the slab, the concrete trucks used were really tiny ("last concrete truck"?), or the OP is yanking our chain.

 

[coloeng]

If he used 2x6 forms, the actual thickness could be 5.5" instead of 5" which could account for the discrepancy. But, he should let us know that he values our input and at least respond.

 

[BridgeSmith]

If he used 2x6 forms, the actual thickness could be 5.5" instead of 5" which could account for the discrepancy. But, he should let us know that he values our input and at least respond.

Still doesn't explain the need for multiple trucks.

 

[coloeng]

Yep, missed the part about the last truck being 1 yard short. Rereading the original post, not much of it makes sense.

 

[Pinwards]

Reading between the lines, I would bet it was a larger pour of the main foundation or other elements, and OP was hoping there was enough left over for the hot tub slab and ran a little short.

#

 

[dkrekelberg]

A little late to the party but you want a wet (no standing water, but wet) substrate for best bonding, with a fractured aggregate or roughened surface. Use a product that is non-shrink and can be applied down to 1/4" thick lift (ideally up to 2" without needing to be extended with aggregate).

I am trying to understand though, the original slab was designed to be 7" thick with #4 bar at 12" o.c. each way? OP must have meant 105 SF, roughly 10ft by 10ft - 105 square inches isn't fitting much on it. The thin layer of topping material will deteriorate over time more rapidly than a monolithic 7" slab, especially with a high heat and moisture service state (hot tub).