Is it ok to pour piers without use of a vibrator
Is it ok to pour piers without use of a vibrator
(OP)
We are concerned about the work a concrete company has done. We learned halfway through the project that they should have been using a vibrator during the pours. We made them use one for the retaining walls, but they had already poured all the piers. The piers are 16' deep, 16" diameter. The cages are 4 vertical bars arranged in an 8.5" square with stirrups every 6". They did shake the top of the cages as the concrete neared the top, but I don't think it was doing too much. Should I be concerned or would the concrete been likely to flow well enough to prevent large voids?






RE: Is it ok to pour piers without use of a vibrator
Check the slump of the concrete and the type of mix. If the mix was a high strength grout mix with a high slump (over 8 inches or so for this application), then vibration wouldn't likely be necessary.
The purpose of vibration is to consolidate the concrete and reduce the number of large voids you can sometimes get through the combination of mix design factors, the slump conditions at the time of placement, and the geometry of the pier/reinforcement interface.
RE: Is it ok to pour piers without use of a vibrator
Piers are a very rugged thing and in most cases the concrete is self consolodating in a vertical shaft configuration.
RE: Is it ok to pour piers without use of a vibrator
Were permanent casings used? Or a tremie method or was the excavation dry enough that the walls of the excavation could be self supporting?
Regards,

Qshake
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RE: Is it ok to pour piers without use of a vibrator
1) Consolidates the interface between successive pours.
2) Eliminates concrete hanging on the reinforcing creating voids within the structure.
If the piers were poured in one continuous pour then you will not have irregularities in the concrete. So check the volume.
Check the concrete tix from the trucks. Compare the recorded volume used from the tix, verses the volume from a quantity take-off from the drawings. If the two differ by a significant volume you might have voids within the pier.
RE: Is it ok to pour piers without use of a vibrator
RE: Is it ok to pour piers without use of a vibrator
Secondly there is the posiibility of coallapse of the bore. Either a casing, bentonite or polymer may have been used. Alternatively the geotechnical engineer may have advised that the vertical face would be self supporting. More information is needed before an opinion can be given on this.
Zambo
RE: Is it ok to pour piers without use of a vibrator
In fact, the older engineers that I learned under used to only specify 2" of clear distance even though ACI calls for 3". The reason was that the rebar supplier would take the specified shaft diameter, say 18", and set his hooping or ties at 18-2-2 - 14" dia. The shaft would end up being 20 to 24 inches and you'd end up with more than the required 3" clear.
RE: Is it ok to pour piers without use of a vibrator
RE: Is it ok to pour piers without use of a vibrator
Zambo
RE: Is it ok to pour piers without use of a vibrator
Check the mix design to see what slump was ordered. It was likely not less than that when placed.