BRAB slab using air entrained vs. non-air entrained 2

[whir]

If you have a BRAB slab on grade design that is poured monolithically with some of the grade beam exposed on the exterior and the slab exposed on the interior, do you use air-entrained concrete or not? My thought is not to because patching an exterior spall is less of a problem than delaminating pockets in an exposed floor finish.

 

[SlideRuleEra]

...patching an exterior spall is less of a problem than delaminating pockets in an exposed floor finish.

I prefer air-entrainment for virtually everything.
Sure would not be using/not using air-entrainment as a band-aid for poor workmanship. See "Concrete Slab Surface Defects: Causes, Prevention, Repair" by Portland Cement Association.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[dik]

Use air entrained throughout... spalling on the interior should not be an issue if finished properly. Air entrainment also makes the concrete mix more 'fluid'. This results in a more 'workable' and easier to place concrete.

Dik

 

[hokie66]

Is BRAB a new kind of concrete? I hate acronyms.

 

[dik]

SRE... an old, but excellent publication.

Dik

 

[dik]

hokie... good question. I've not heard of it either.

Dik

 

[hokie66]

Must be a US thing. I am too lazy to Google it.

 

[Ron]

Building Research Advisory Board technique....archaic and rarely used.

 

[dik]

thanks, Ron... I've never heard the term... my sheltered existence.

Dik

 

[jayrod12]

I believe the type of finishing technique also plays a role in whether you want an air entrained slab or not. My memory is foggy but a steel trowelled finish may cause the bubbles to rise to the surface.

 

[dik]

Depends on a few thing... timing and degree of the steel trowelling is one are some of them...

Dik

 

[whir]

Where I started with this question was a Portland Cement Association web page advising against hard troweling air entrained concrete:

https://www.cement.org/learn/concre...construction/finishing-air-entrained-concrete

As well as the American Society of Concrete Contractors advising against it:

https://www.ascconline.org/Portals/...d-trowel-finish-on-air-entrained-concrete.pdf

 

[HuckleberryFinn]

As Ron says, it's an old Texas documents for sizing waffle slabs in expansive soils. I think most folks are using the WRI method these days (at least, that's what we use).

 

[JoelTXCive]

The 1968 Building Research Advisory Board (BRAB) "Report No. 33" was prepared by the National Research Council (not sure who that is) for the U.S. Federal Housing Administration (FHA).

My understanding is that it was groundbreaking because it led to the widespread acceptance of the residential "California Slab" (thickened perimeter slab) and "Texas Waffle Slab" (ribbed slab). I think that after this report the FHA and other lenders were clear to lend money on homes with these type slabs, which meant the builders in the Southern & Western US had a green light to start using them everywhere.

I do not think the design procedure is used much anymore, but it does serve as a basis for the WRI method and PTI method. You still see references and citations to the BRAB #33 every now and then.

Attached is a digital copy. (Slide Rule might want to put it in his collection) I've looked for a used hardcopy, but not come across one. (I think it is a unicorn)