My experience has been that the grout used for setting and leveling the panels should be a non-shrink grout, (2 erection beds each panel), but the concrete between the bottom of the panels and continuous footing, (assuming a cont. footing and not isolated pads), is a normal pea grafel mix and is usually poured with the adjacent "pour strip." The gap between the bottom of the panels and top of the footings is usually about 2".
If non-shrink grout is required, I will specify it continuously to get uniform support. Friction probably is not a concern because it is related to total vertical load and surface condition but not total contact area.
Lutfi: It is interest to know that you lost every fight. Can you give more details? I assume that you are the Engineer of Record, can you refuse the contractor's work? Did the inspector sign off the work? Can the owner refuse to pay (at least deduct the price difference)?
I worked as an quality assurance engineer for a multi-billion project. When casting slab on grade or on metal deck, all top WWF was stepped to the bottom. The engineer of recore and inspector didn't care. And since the organization is very big, no body in the owner's team cared, too. I'm afraid the same thing will happen for the tilt up panels. If top bars are stepped down, there will be structural cracks under wind.
Lutfi... can you certify with the note '... was in general compliance with the approved documents, except...' and if it is an issue, then require that the Contractor obtain an engineering opinion that the manner of construction is adequate?
That reminds me of when I tried to force them to chair the WWF instead of using the highly ineffective pull method where 5 guys stand on the WWF while one is pulling it up as the concrete is being poured. I got the argument from them that it was standard practice and nothing detrimental could be proven by using this method. Then, the contractor wanted to go to the owner and say we are holding up construction by stopping what they consider standard practice. The problem is that it becomes an argument of means and methods versus what I feel like should be done.
It seems like you could write in your specs to have the grout placed prior to placing the tilt panels if you are worried about the soupy mix. I think you should be able to write in your specs any forbidden construction method if you feel it negatively effects the structural adequacy of the building. If he doesn't like it, tell him he shouldn't have accepted the contract with the way the specs were written.
The "pull" method is simply a joke. When you stand on the WWF, your body weight prevents you from pulling up the WWF.
If you can achieve the specified concrete cover in your way, it is your means and methods. If you cannot, it is non-compliance.
I don't think bar chair is a practical way to support WWF. To prevent WWF from being stepped down, the chairs may need to be at 6" or 8" spacing. The only way I think will work is to make many "stools". The workers must stand on the stools and move the stools when they need to move. I don't have enough courage to propose this in a real job yet. For slab on grade or on metal deck, top bar location is not a serious structural issue; for tilt up panel, however, it is. I guess that conventional bar chair spacing is for the bar selfweight plus a little bit incidental load. I'm not sure whether it is practical to use bar chairs for #5 bars to support a 200LB construction worker.
The purpose of the grout between the tilt up panel and the footing is to eliminate any possible gap; therefore, it should not be poured before erection.
