New Conc. Topping Slab on Exist SOG
New Conc. Topping Slab on Exist SOG
(OP)
I have retail store with an existing concrete slab on grade. The client wants to raise the perimeter of the store (about 50% of the entire floor area) 2.5 inches. Portions of the new floor will be tiled, while the rest will be finished smooth.
I searched the threads for concrete topping slabs with no definate concensus.
My concerns are cracking of the 2.5" topping. Some have mentioned using WWM, others mention using fibers. I'm leaning towards the WWM on chairs, but worried about accurate placement. Fibermesh is tough to finish, and from what I've seen, leaves a "hairy" finish.
Any thoughts, recommendations?
I searched the threads for concrete topping slabs with no definate concensus.
My concerns are cracking of the 2.5" topping. Some have mentioned using WWM, others mention using fibers. I'm leaning towards the WWM on chairs, but worried about accurate placement. Fibermesh is tough to finish, and from what I've seen, leaves a "hairy" finish.
Any thoughts, recommendations?






RE: New Conc. Topping Slab on Exist SOG
Are you using bonded or unbonded topping?
Take great care in providing sufficient control joints.
RE: New Conc. Topping Slab on Exist SOG
You're right on - provide plenty of control joints. I'll hear an ear-full if this topping cracks!
RE: New Conc. Topping Slab on Exist SOG
Small cracks in the tiled area should not be an issue if a flexible tile adhesive is used.
I would specify a bond breaker between the two slabs, either liquid applied or a plastic sheet.
RE: New Conc. Topping Slab on Exist SOG
Does anyone think a 4ksi mix over a 3ksi mix would be beneficial?
RE: New Conc. Topping Slab on Exist SOG
RE: New Conc. Topping Slab on Exist SOG
engr. rejido
RE: New Conc. Topping Slab on Exist SOG
Hopefully you have an owner who is aware that there will be some slight cracking visible in the exposured surfaces no matter what is done.
Providing WWF reinforcing, with a bond breaker and plenty of joints will certainly help keep cracking to a minimun, but I would make it clear to the owner that he should not expect to see a 100% crack free surface when its done. Its just the nature of the concrete to crack.
Unfortunately, over the years, I have found this is not the expectation of all owners when dealing with exposed concrete floor.
Just my 2 cents worth.
RE: New Conc. Topping Slab on Exist SOG
RE: New Conc. Topping Slab on Exist SOG
RE: New Conc. Topping Slab on Exist SOG
Shrinkage reinforcement does not prevent cracking, it controls the width of the cracks.
cvg,
You don't want a bond breaker if the tiles are thin set, but a flexible adhesive is necessary. A bond breaker could be used under thick set tiles, but I don't think the OP contemplated a thick set method.
RE: New Conc. Topping Slab on Exist SOG
RE: New Conc. Topping Slab on Exist SOG
The bond breaker and plenty of joints is a good idea.
Also:
Specify that there is to be a joint in the topping slab over every existing joint.
Specify that the tiled finishes are to have joints over your slab joints.
I would also specify that the slab be left for at least 2 weeks (or more) prior to tile placement to allow for a lot of the shrinkage to take place.