Paint Post-tensioned cables
Paint Post-tensioned cables
(OP)
Folks,
I am trying to specify on the drawings to spray paint the P/T cables location on the forms with a spray paint prior to placing concrete so that the locations can be seen from below after the slab forms are stripped.
Has anyone specified this before and if yes, is there a particular paint product that was used?
I am trying to specify on the drawings to spray paint the P/T cables location on the forms with a spray paint prior to placing concrete so that the locations can be seen from below after the slab forms are stripped.
Has anyone specified this before and if yes, is there a particular paint product that was used?






RE: Paint Post-tensioned cables
RE: Paint Post-tensioned cables
So, would a slower-drying brushed on latex be better?
A string laid on the form would be "picked up" by the concrete - but would probably be moved too if it weren't tied at both ends by a nail. The string would leave a "line" in the concrete so you could avoid drilling through the rebar/tensioning wires.
RE: Paint Post-tensioned cables
Mike McCann
MMC Engineering
RE: Paint Post-tensioned cables
RE: Paint Post-tensioned cables
Just going by the slab edge to locate tendons is very innaccurate. The tendons may curve laterally, and typically spread out at the ends. Also, the slab edge is patched and finished over the end caps, so in the finished product, you won't see them anyway. But if you have drop ceiling, the paint will always be visible.
If you are planning to have exposed unfinished concrete, say in parking garage, then you may want to use chalk lines, as I think these may be easier to pressure wash off down the road.
RE: Paint Post-tensioned cables
RE: Paint Post-tensioned cables
RE: Paint Post-tensioned cables
Many a time the MEP guys want to install something overhead. From time to time we have had them hit the low point of a cable group and caused all sorts of headaches.
We want to be able to locate the tendons so that people who are trying to drill from below know where the cable is.
RE: Paint Post-tensioned cables
RE: Paint Post-tensioned cables
They are talking about marking slab tendons so they can be located in the future, when additional penetrations may be required.
structuresguy,
You want the markers to stay in place, not able to be removed by pressure washing. But I suppose that doesn't stop the owner from covering them up by painting the soffit.
slickdeals,
The staples used to hold the ducts in place are usually found quite easily, and painting on the form helps to define the line. I have seen plastic tape used, at several points along the tendon, but it doesn't stick well to oiled forms, so sometimes gets dislodged. If it floats up in the concrete, the thin layer of concrete under the tape spalls off, so I don't like that approach.
RE: Paint Post-tensioned cables
Dik
RE: Paint Post-tensioned cables
When you all come up with the perfect way to permanently leave evidence of the P/T cable locations in the slab soffit, please let me know.
I presume we are talking about unbonded tendons NOT installed a ducts.
Spray-painted lines on the top of the forming deck work, and the paint will transfer to the concrete. Should be reapplied for the next level. In a ceiled area the paint lines should not be objectionable, but I can't say how permanent they will be. In an exposed situation (such as a garage) I suppose a pressure-washing would remove the paint.
Tape, string, etc. are not reliable as they will get dislodged during concrete placing opperation.
Perhap a 1/4" thick X 3/4" wide reveal stapled to the formwork directly below the cable would be ideal. It'll leave a groove in the slab soffit that will be visible forever, yet is shallow enough to not severely impact cover. But I can hear the contractors screaming already about labor involved to install.
Having spent a few decades in the concrete construction industry I felt compelled to comment.
Ralph
Structures Consulting
Northeast USA