Infilling at Depressed Concrete Slab on Grade
Infilling at Depressed Concrete Slab on Grade
(OP)
The contractor poured a portion of a slab on ground 2-1/2" too low. He thought it was a depressed slab, but it is not. The existing slab is 6 inches thick with 4x4 W4.0xW4.0 WWF. The rooms are mostly for storage and will have vinyl composition tile.
The contractor's solution is to apply a bonding agent and infill the 2 -1/2" with a 4,000 psi grout. I have asked that he submit a mix design along with break data.
This seems acceptable to me, what do you think?
The contractor's solution is to apply a bonding agent and infill the 2 -1/2" with a 4,000 psi grout. I have asked that he submit a mix design along with break data.
This seems acceptable to me, what do you think?






RE: Infilling at Depressed Concrete Slab on Grade
RE: Infilling at Depressed Concrete Slab on Grade
Consider pinning the topping to the existing slab.
RE: Infilling at Depressed Concrete Slab on Grade
What would be the difference between 4,000 psi grout and 4,000 psi concrete? Given that the thickness is only 2-1/2" what maximum size of aggregate would you recommend?
Wouldn't a mix similar to that used for composite precast concrete plank be suficient?
RE: Infilling at Depressed Concrete Slab on Grade
The coarse aggregate should be #89 stone, although for 2-1/2 inches, you could use #57 stone...but might be a bit difficult to finish.
RE: Infilling at Depressed Concrete Slab on Grade
Regardless of w/c ratio, the amount of water in the mix has a direct effect on the shrinkage. The smaller the aggregate, the greater the surface area/volume of the aggregate is. The greater this ratio is, the more cement that is needed. The more cement you have, the more water you have (simply by virtue of the w/c ratio - double the cement, double the water) the more shrinkage you get.
Grout is really just sand, cement, and water. You can't get aggregate smaller than sand, the so the surface area/volume ratio is very high. As Ron noted, this requires a lot of cement, which, in turn, requires a lot of water.
RE: Infilling at Depressed Concrete Slab on Grade
RE: Infilling at Depressed Concrete Slab on Grade
RE: Infilling at Depressed Concrete Slab on Grade