Auger cast piles

[MotorCity]

We are using auger cast piles that are grouted (as opposed to constructed of concrete). They will be reinforced with a cage and a single bar in the middle of the pile. Reinforcement will not extend to the full length of the pile.

My question is this, is there anything in ACI that addresses the design of structural grout? In other words, do the same principles apply to "structural" grout as for structural concrete? I would assume that the same principles would apply, but I am not sure if ACI specifically allows or addresses this.

To my knowledge, the main difference between concrete and grout is the size of the coarse aggregate (if any).

(The client and contractor have mandated the use of grout, so changing to concrete is not an option.)

 

[Archie264]

You say that "the client and contractor have mandated the use of grout, so changing to concrete is not an option" but who is the design engineer of record? Has he either concurred or issued an objection? The one who gets to make the call is the one who's taking legal liability for the design.

 

[dcarr82775]

What do you mean by grout? A neat cement grout will shrink a lot which could lead to problems. A 'grout' that is more like a concrete mix with 3/8" aggregate would be more acceptable.

Is the center bar at least full length?

 

[MotorCity]

We are the EOR, and at this point we have no reason to believe that grouted piles won't work in terms of strength or constructability. Grouted piles are pretty common in the area where the project is located. My past experience only involves concrete piles.

I am not sure yet of the mix design, but it will have to be grout with fairly small aggregate. It will be placed under pressure through a pipe or tube located in the center of the drill shaft. The grout will flow out as the auger is withdrawn.

The bar is not full length because some of the piles are 100+ feet long and the bar serves no purpose at that depth.

 

[JedClampett]

Augercast piles are normally made with grout. The material needs to be pumped under pressure into a 3 inch pipe, so regular concrete jsut isn't runny enough.
There's nothing in ACI either way. Grout is just a different concrete mix containing no coarse aggregate. The augercast capacity is usually pretty small in relation to the concrete strength. For instance, a 50 kip capacity on a 14 inch augercast only causes a 325 psi compression stress.
As far as shrinkage and other issues with grout, if they happen, they haven't caused any problems with the thousands of augercast piles installed already.