Void around the center bar of an Auger Cast Grout pile

[JKJohn]

We have done 24" Auger Cast Grout piles. The piles have a center bar and a cage bar. The piles were over poured by 3 feet (as designed). During chipping the extra 3-feet we found a void around the center bar at the bottom of the extra grout.

The contractor said this is typical. They claimed that the center bar draws water which causes the void.

Has anyone seen this before? and is it really that common?

 

[oldestguy]

Not seen, but I surmise while inserting it that it dragged grout along with it and of course that grout had to come from some place.

 

[PEinc]

Sounds fishy to me.

http://www.PeirceEngineering.com

 

[Retrograde]

If the void is caused by bleed water rising through the concrete then it means that you need to modify your mix design.

 

[GeoPaveTraffic]

Sounds to me like the grout had started to cure before the center bar was inserted.

Mike Lambert

 

[JKJohn]

Very interesting. One more idea from a coworker, the center bar had dirt on it.

The contractor proposed plan is to clear around the center bar going deep until the grout is well placed around the bar, then fill the void with some sika product. They are very confident that this is limited.

At this point, there is no way to verify that this condition is not repeated. For small voids, I have no doubt the pier will perform. The problem is there is no way to verify (other than testing it, which could not be done.)

Any recommendations?

 

[ATSE]

Retrograde is correct. The mix most likely needs special admixtures.
Check out Specrete or common VMAs available from BASF, Euclid...

 

[Ron]

Steel does not "draw" water. The void is either a void from lack of consolidation or from bleed water. The size of the void, its orientation and its surface characteristics will tell the source of the issue.