Aquatic Technology Pool & Spa, "Creating Water as Art."™

Aquatic Technology Pool & Spa, "Creating Water as Art."™
Pools as an art form - the way it should be!

Friday, November 30, 2012

Cracking Concrete Pool Decks

Swimming pool concrete deck expert witness Paolo Benedetti, discusses improper slab thickness and the lack of proper reinforcement steel placement.

The Concrete Pool decks are cracking
There is no code that requires reinforcing steel within non-structural concrete "slabs on grade."  However, if any reinforcement is used, then the codes are very explicit as to where and how it is to be placed.

There ought to be a law!
The Uniform Building Code makes direct reference to the standards established by the American Concrete Institute.  For slabs poured on grade there must be a minimum of 3 inches of concrete between the reinforcement and the earth.  It also states that there must be a minimum of 1.5 inches of concrete on top of the reinforcement (side exposed to the weather).

ACI Standards require a Minimum Slab Thickness 
Because the ACI specifies the amount of concrete around the reinforcement, it de facto creates a standard for minimum slab thicknesses.

If #4 reinforcement steel is used to reinforce a slab on grade, then the slab must be a total thickness of no less than 5.5 inches.

1.5 inches of coverage over the steel
1 inch of steel (#4 bars are 0.5 inch thick, where two #4 bars cross there is 1" of steel)
3 inches below the reinforcement steel
1.5 + 1 + 3 = 5.5" minimum slab thickness (when using #4 bars).

2x4 Formwork is INCORRECT!
2x4's are actually 3.5" wide.  Therefore there is no means for a concrete contractor to pour concrete slabs of sufficient thickness if they utilize 2x4's as forms!

2x6's are 5.5" wide.  They are the MINIMUM sized lumber that should be used when placing concrete slabs.

The ACI standard applies whenever reinforcement is used within the concrete.  This even means when they use #10 wire mesh, that they must support the reinforcement so that it is placed in the proper location within the slab.

"Hooking" the wire mesh & lifting it up into the wet concrete will not place the mesh in the proper location. 

This is why most concrete slabs are cracking, too thin, incorrectly formed and with the steel in the wrong location! 

Paolo Benedetti - Aquatic Artist
"Creating water as art."™
 Aquatic Technology Pool and Spa