Problem with Dirty Concrete - Bored Piles
Problem with Dirty Concrete - Bored Piles
(OP)
Currently we are having issues regarding the integrity of our bored piles. Our project is a residential building with 20 floors. We are using dry method when we construct the bored pile since bedrock is very shallow (less than 6 meters from Natural Grade Line)
After subjecting in cross hole sonic logging test, the third party contractor of the tes advise us that our bored piles have issues in the upper layer (2-4 meters). They are thinking that is due to dirty concrete that was not expelled in the construction process. In this light, would like to create a discussion 1) What is the best method of expelling dirty concrete from your experience 2) What is the chance that the cross hole sonic logging test may be receiving bad signals and may not be entirely reliable?
After subjecting in cross hole sonic logging test, the third party contractor of the tes advise us that our bored piles have issues in the upper layer (2-4 meters). They are thinking that is due to dirty concrete that was not expelled in the construction process. In this light, would like to create a discussion 1) What is the best method of expelling dirty concrete from your experience 2) What is the chance that the cross hole sonic logging test may be receiving bad signals and may not be entirely reliable?





RE: Problem with Dirty Concrete - Bored Piles
RE: Problem with Dirty Concrete - Bored Piles
How large a diameter are your end bearing piles?. Unless you are on granite or something of that ilk, I would think your shafts would be in the order of 900-1000mm dia. How are you inspecting the bearing surface (for a 20 storey building, I'd do that) How heavy are your loads? What is your bearing value? I assume bedrock is 'flat'. How highly stressed is the concrete? How is the contractor cleaning the holes? at bedrock? What is dirty concrete? What is the condition at the pile/bedrock interface?
Dik
RE: Problem with Dirty Concrete - Bored Piles
RE: Problem with Dirty Concrete - Bored Piles
RE: Problem with Dirty Concrete - Bored Piles
Dik
RE: Problem with Dirty Concrete - Bored Piles
RE: Problem with Dirty Concrete - Bored Piles
Dik
RE: Problem with Dirty Concrete - Bored Piles
Check if the sonic tube are mada of steel. PVC should not be used because lack of adherence between concrete and PVC can alter the signal.
RE: Problem with Dirty Concrete - Bored Piles
RE: Problem with Dirty Concrete - Bored Piles
You should not have problems concreting dry. I believe the sonic tests can be questioned.
However if the slump value of the concrete is not maintained above 16 cm during the complete concreting section you might have dirty concrete inclusions in the sound concrete. This is because the concrete of the tremie tube goes up alongside the tremie tube instead of being well distributed. At one stage the concrete level is much higher close to the tremie pipe than on the outside of the pile and then can overflow the dirty concrete from the bottom of the excavation.
One way to know is to ask the concrete foreman if he encoutered difficulties with the flow of concrete in the tremie pipe in the last meters of concreting.
Anyway since depth of defects is not that big, you should try to expose alleged defects. If they don't show up, it means that the sonic test contractor proficiency should be questioned. Alternatively you could bring another company (provided you are sure they are working well) to do the tests again.