Bonded topping joints
Bonded topping joints
(OP)
With a bonded topping (1 1/2" over 4 1/2" slab), with joints cut about every 12 to 14 feet, would you expect the topping to shrink to a degree that sawcut joints filled with semi-rigid epoxy would tear?
Interior slab - normal weight - bond was tested for tensile-bond limits and passed. Joints about a sawblade wide.
Interior slab - normal weight - bond was tested for tensile-bond limits and passed. Joints about a sawblade wide.






RE: Bonded topping joints
Just did a petrographic examination on a similar condition here locally. Two-inch topping over five inch slab....So much shrinkage that debonding occurred over most of the slab. It had some construction problems as well, though.
RE: Bonded topping joints
Pumped mix. 3/4" aggregate I believe.
I just have a hard time "seeing" a bonded topping (we bond tested the heck out of it) shrink when it is bonded to an older underlying slab.
RE: Bonded topping joints
RE: Bonded topping joints
I don't know if you've measured the joint width now relative to the saw blade width at the time of sawing, but that would give a magnitude of shrinkage.
Any chance that the joint width was very small right after saw-cutting and that there was not sufficient width to get a proper sealant profile? If so, then the sealant might be giving a false indication of the joint shrinkage.
Also, keepin mind that you probably measured tension bond when the failure mechanism for bond failure is going to be shear. Figure the shear bond to be a small fraction of the tension bond.
RE: Bonded topping joints
RE: Bonded topping joints
RE: Bonded topping joints
RE: Bonded topping joints
RE: Bonded topping joints
The joints have cracked - primarily through the epoxy with only minimal bond loss between concrete and epoxy.
With 24% there isn't much room for movement - but again, since it was bonded, I would think the shrinkage ...at the joint....would be minimal. 12 ft. to 14 ft. centers on the sawn joints. So the question is basically, at 21 days of age (the underlying slab was older) would a 1 1/2" bonded topping stretch a sawn joint more than 24%? (i.e. the final joint width is 124% of the original)
RE: Bonded topping joints
"The joints have cracked - primarily through the epoxy" & "The filler was a semi-rigid epoxy with an elongation capability of 24%."
How exactly the crack looks? Can you post a photo?
RE: Bonded topping joints
How much separation is there at the sealant crack? The amount of separation should mimick the total joint movement, since cohesive not adhesive failure occurred.
RE: Bonded topping joints
RE: Bonded topping joints
I'll see about posting a photo tomorrow.