Thickened slab edges have been in use around the exterior perimeter of wooden block-out forms for many years. It wasn’t that thickened slabs were preferential - it was simply a matter of being the “lesser of two evils”. When a contractor chooses to cast the slab prior to steel column erection, that contractor must build a wooden box with all exterior dimensions equivalent to the required isolation pocket that will be enclosed. Obviously, prior to casting the interior void (isolation pocket), other items must be completed... The wood must be removed and...The column must be erected in its final position.
What caused the need for the thickened slab edge was the fact that subbase material under the slab must have confinement. The wooden box provides this confinement temporarily, but the confinement was lost the very minute that the wooden box is removed. It is for this reason that subbase material so often “caves-in” when the wooden box is removed. Admittedly, some soils are more prone to “cave-ins” than others. Weather conditions can be a cause for “cave-ins” of otherwise cohesive soils.
To prevent the pre-described “cave-ins” from occurring, many contractors chose to thicken the edge of the slab - in order for the subbase material to maintain confinement after removal of the temporary wooden boxes. Unfortunately, the thickened slab edges solve the “cave-in” problem, but offer detrimental by-products such as:
(1) Additional expense - more concrete costs more money
(2) Modified slab behavior - slab movement to accommodate concrete shrinkage is considerably hampered.
(3) Conduit or piping penetrations are compromised.
The ideal formwork for an isolation pocket must be able to:
(A) Permanently confine subbase material,
(B) Eliminate the need for slab thickness variations,
(C) Easily and permanently conform to penetrations, and
(D) Allow a variety of concrete placement schedules.
POCKET FORM ISOLATOR does all of these things and much more! PFI is very “stealth” in that it is hardly detectable in a finished slab. Because no thickened slab is necessary, PFI enables the contractor to reap the benefits of:
(1) No wasteful expense of thickened slab edges,
(2) No unsightly chipped edges from removal of wooden boxes,
(3) No damaged conduit or piping penetrations.
*Due to the unique material properties of POCKET FORM ISOLATOR , some other benefits may prove additionally beneficial to the user.
*The cost of a completed isolation pocket where PFI was utilized is considerably less than the completed cost of an old-fashioned unit.
*The functionality is greatly enhanced - because true separation occurs via material that does not permanently bond to concrete.
*Compressive expansion material is never required due to the simple physics that work in your favor.
*Polyethylene backer rod is not required for caulking isolation pocket edges - because PFI itself is made of polyethylene.
As stated before, POCKET FORM ISOLATOR enables its users to benefit from an additional construction sequence that has never before been available - simultaneous slab and isolation pocket casting. Since compressive expansion material is not necessary in conjunction with PFI , the required separation is inherent - due to material properties that work in your favor. You can say “good-bye” to the old fashioned “stop and start” casting sequence on many of your projects! How in the world can someone expect to successfully remove a wooden box without damaging a penetrating conduit or pipe? With the POCKET FORM ISOLATOR broken conduit caused by removal of temporary wooden forms becomes a bad memory from the past.