Taking concrete cube samples from overflow of bored pile

[bonboncats]

Hi All,
just want to hear your opinion about whether the concrete cube sample can be taken from the overflow of concreting work (bored pile) instead before placing the concrete in the bore shaft. because the cube sample may not reflecting the actual concrete strength since it is diluted with water.

Does this ever been done in construction of bored pile?

 

[EireChch]

The two strengths should be the same. On the limited times I have been on site for this it was just taken from the tremie pipe or off the back of the chute.

Your concrete shouldnt be getting diluted with water. I imagine that there maybe some water added to the mix from the concrete plant to site as it travels in the concrete truck. I would think that this is accounted for though.

However on site you should be pouring concrete in dry holes or using a tremmie to start pouring concrete at the bottom to displace the water.

 

[SlideRuleEra]

bonboncats - I agree with you, the sample from the unconfined overflow is likely to be somewhat segregated and is not representative of the concrete in the shaft (which is confined by the shaft walls).

http://www.SlideRuleEra.net

 

[EireChch]

SRE but is it likely any different from the stuff from the chute of a truck ?

 

[BigH]

The bottom line - what you are doing or considering or just being inquisitive is not in accordance with ASTM nor with EN or BS EN. If there is ever a problem, you will be toast . . .

 

[SlideRuleEra]

ErieChch - The way I read the OP's question, he is asking about taking the sample from the overflow at the top of the pile. That is, after the concrete has passed completely through the tremie, the bored hole is totally filled with concrete, and the overflow at the top of pile takes place as the very last of the concrete is being placed... but the sample is not the very last concrete being placed.

This overflow concrete will be very different from the concrete that came out of the truck. A few examples...

How long has the overflow concrete been in the bored hole?
Who knows... maybe the concrete had even been in the truck too long.

What was the temperature or slump of the overflow concrete when initially placed?
Who knows... maybe it was out of spec when it came out of the truck and that load should have been rejected before placement.

For large bored piles, say 4' diameter, 40' long (18.6 yd²), which truck did the the overflow concrete come from?

As BigH says, the problem with sampling this overflow concrete comes when thing go "wrong"... overflow concrete samples will not give any accurate clues.

http://www.SlideRuleEra.net

 

[EireChch]

SRE - I see your points, cheers.