Reinforcement cover
Reinforcement cover
(OP)
According to ACI, concrete cast against and permanently exposed to earth is to have a minimum cover of 3" (ACI 7.7.1). Does this apply when placing concrete on crushed stone? I cannot find any further commentary on this in ACI nor any other text. What is the common practice?





RE: Reinforcement cover
RE: Reinforcement cover
What does everybody think?
RE: Reinforcement cover
In addition to the basic irregularity of the earth, there is also the potential for the reinforcing to "loose" some of its cover due to:
1. Pumping of the earth due to wheel or foot traffic.
2. Sinking of chairs into the earth (concrete puddlers typically walk on the rebar, driving the chairs into the ground.
3. Rocking of chairs due to the irregularity.
4. Movement of the subgrade due to concrete, in mass, flowing onto the earth.
All of the above are more critical to the rebar in that the "exposed to earth" leaves the rebar open to moisture fluctuations that ....well, you know what that does to steel.
RE: Reinforcement cover
When cast against a form, there is no migration of moisture outward and the paste is comparatively dense, thus inhibiting inward migration of future moisture.
RE: Reinforcement cover
RE: Reinforcement cover
RE: Reinforcement cover
In an expansive clay situation, your 5" slab reinforcing is not going to really help in adding stiffness to your slab to help in structural behavior during shrink/heave cycles, especially if its in the middle. I would still want the rebar in the top to keep cracks closed on the surface, knowing I've got larger crack widths developing in the lower regions.
If I want to stiffen the slab to minimize localized heave, I would use a stiffened slab made up of monolithic concrete ribs, or beams, in a grid pattern under the slab.
RE: Reinforcement cover