Concrete Cover
Concrete Cover
(OP)
I am interested in board members views about concrete cover and construction joints.
Over the years if the drawings show either a column penetrating into a slab or beam or a bored pile penetrating into a pilecap I would allow the horizontal bars to sit directly onto the construction joint.
For clarity if this was a pilecap with specified 75mm cover to the bottom layer of rebar I would have the pile cut off at +75mm then place the first layer of rebar directly on the bored pile. But I am now on a project (still at design stage) where the designer is insisting that spacer blocks of minimum 50mm must be placed on the top of the cut off pile. This means that to satisfy the condition of pile cut off 75mm above the pile cap base then I must have 75 + 50mm = 125mm cover (although tbe specified cover is min 75mm).
Is there a correct way of doing this or is it variable depending on interpretation?
Over the years if the drawings show either a column penetrating into a slab or beam or a bored pile penetrating into a pilecap I would allow the horizontal bars to sit directly onto the construction joint.
For clarity if this was a pilecap with specified 75mm cover to the bottom layer of rebar I would have the pile cut off at +75mm then place the first layer of rebar directly on the bored pile. But I am now on a project (still at design stage) where the designer is insisting that spacer blocks of minimum 50mm must be placed on the top of the cut off pile. This means that to satisfy the condition of pile cut off 75mm above the pile cap base then I must have 75 + 50mm = 125mm cover (although tbe specified cover is min 75mm).
Is there a correct way of doing this or is it variable depending on interpretation?






RE: Concrete Cover
RE: Concrete Cover
thanks
chris magadia
www.chrismagadia.com
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RE: Concrete Cover
Another detail I have used for 2 pile caps with bar arrangements similar to a beam is to have the links sit on top of the piles. This has typically been used if the piles are a larger diameter than the link spacing. This results in 75 cover to shear links and 87 to main longitudinal bars ( assuming 12 diameter links.)
RE: Concrete Cover
BA
RE: Concrete Cover
RE: Concrete Cover
Also - over pile caps, there are no development needs at that point so lack of competent concrete all around the bar is not necessary.
RE: Concrete Cover
As far as needing confinement for development and splices, these would be a consideration in certain instances, and I don't think you can make a general statement that competent concrete is not needed. One other possible consideration is that rotation of the pile could compromise the reinforcement if there is direct contact.
I'm not sure why you are concerned with having addition cover. The 75mm minimum (3" in the states) reflects it being cast against soil, because of the inherent irregularities in that process, as well as potential exposures.
RE: Concrete Cover
It would depend what the rebar is doing at that point. Maybe not a huge concern if you're just using it for shrinkage, but if it's doing something I'd look a little more closely maybe.
RE: Concrete Cover
So are you saying that for a concrete pile projecting 4" into a pile cap, there should be 7" cover to the soil under the bottom bars of the pile cap? I have never seen it done that way, and it seems very wasteful.