Auger cast grout and sample size

[Jabson]

Can anyone either show me or tell me where to find the reason why augercast grout sample sizes are 2x2 or 2x4? I have an out of state engineer who requires 6x12 cylinders for augercast grout. And he informes me that unless I can show why 2x2 or 2x4 break more accuratly and consistently than 6x12, our special inspectors will be making 6x12's.

 

[dirtsqueezer]

Well, actually, the thing is with augercast grout is that pea gravel. Small cubes do take grout, but that's sandy grout, not 3/8" grout. You might be thinking base plate grout. I'm pretty sure the last time I made samples for augercast piles I made 4x8s, not 6x12s, but it was definitely a cylinder of some type.

Watch that grout, too. The last time I did it the concrete company tried to pass off a regular 3/4" mix with loads of water added to make it look like grout; basically a lean mix. Sampled it, of course, and low and behold, they came up something like 2 or 3 thousand pounds short. I hoped that the engineer made them redrill, but I they had no access by then, and I think they just went ahead. Bad business all around. But better to know that 'grout' was bad than not at all. At least they could have designed around it. (Though I don't think they did

 

[dirtsqueezer]

addendum:

I have to ammend this. I thought about it today, and it was another job that we used 4x8 cylinders for, not the augercast pile job. I've been on two of these, both times I used 2x2 cubes. There are ASTMs governing the sampling of grouts, but to my knowledge there's no table spelling out maximum aggregate size corresponding to sample size. Sorry about your predicament. Hope that helps, a bit.

I'm not sure how you would reason with a PE that requires historical testing for consistency, given that you would have to perform trials and such, not timely or cost effective. I would just say that given the aggregate size, namely sand, 2x2s are more economical than 6x12s. ASTM C31 spells out mazimum size aggregate v. sample container and the trend goes larger with larger MSA, and smaller with smaller MSA. It seems also that you would get different results from a 1/1 ratio break than with a 1/2 ratio break. That and I've never heard of anyone making 6x12s out of grout. That's just not how it's done.

That's the best I can do! Good luck.

 

[Jabson]

Thanks, I gave all the data I could to the contractor and testing agency, and have not heard anything back. I think the engineer went with smaller, since I have not got a call from the testing agency or inspector.