// CODE SNIPPET
20.5 Provisions for Durability of Steel Reinforcement
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20.5.1 Specified Concrete Cover
20.5.1.1
Unless the general building code requires a greater concrete cover for fire protection, the minimum specified concrete cover shall be in accordance with 20.5.1.2 through 20.5.1.4.
20.5.1.2
It shall be permitted to consider concrete floor finishes as part of required cover for nonstructural purposes.
20.5.1.3 Specified Concrete Cover Requirements
20.5.1.3.1
Nonprestressed cast-in-place concrete members shall have specified concrete cover for reinforcement at least that given in Table 20.5.1.3.1.
Table 20.5.1.3.1—Specified concrete cover for cast-in-place nonprestressed concrete members
| Concrete exposure | Member | Reinforcement | Specified cover, in. |
|---|---|---|---|
| Cast against and permanently in contact with ground | All | All | 3 |
| Exposed to weather or in contact with ground | All | No. 6 through No. 18 bars | 2 |
| No. 5 bar, W31 or D31 wire, and smaller | 1-1/2 | ||
| Not exposed to weather or in contact with ground | Slabs, joists, and walls | No. 14 and No. 18 bars | 1-1/2 |
| No. 11 bar and smaller | 3/4 | ||
| Beams, columns, pedestals, and tension ties | Primary reinforcement, stirrups, ties, spirals, and hoops | 1-1/2 |
20.5.1.3.2
Cast-in-place prestressed concrete members shall have specified concrete cover for reinforcement, ducts, and end fittings at least that given in Table 20.5.1.3.2.
Table 20.5.1.3.2—Specified concrete cover for cast-in-place prestressed concrete members
| Concrete exposure | Member | Reinforcement | Specified cover, in. |
|---|---|---|---|
| Cast against and permanently in contact with ground | All | All | 3 |
| Exposed to weather or in contact with ground | Slabs, joists, and walls | All | 1 |
| All other | All | 1-1/2 | |
| Not exposed to weather or in contact with ground | Slabs, joists, and walls | All | 3/4 |
| Beams, columns, and tension ties | Primary reinforcement | 1-1/2 | |
| Stirrups, ties, spirals, and hoops | 1 |
20.5.1.3.3
Precast nonprestressed or prestressed concrete members manufactured under plant conditions shall have specified concrete cover for reinforcement, ducts, and end fittings at least that given in Table 20.5.1.3.3.
Table 20.5.1.3.3—Specified concrete cover for precast-nonprestressed or prestressed concrete members manufactured under plant conditions
| Concrete exposure | Member | Reinforcement | Specified cover, in. |
|---|---|---|---|
| Exposed to weather or in contact with ground | Walls | No. 14 and No. 18 bars; tendons larger than 1-1/2 in. diameter | 1-1/2 |
| No. 11 bars and smaller; W31 and D31 wire and smaller; tendons and strands 1-1/2 in. diameter and smaller | 3/4 | ||
| All other | No. 14 and No. 18 bars; tendons larger than 1-1/2 in. diameter | 2 | |
| No. 6 through No. 11 bars; tendons and strands larger than 5/8 in. diameter through 1-1/2 in. diameter | 1-1/2 | ||
| No. 5 bar, W31 or D31 wire, and smaller; tendons and strands 5/8 in. diameter and smaller | 1-1/4 | ||
| Not exposed to weather or in contact with ground | Slabs, joists, and walls | No. 14 and No. 18 bars; tendons larger than 1-1/2 in. diameter | 1-1/4 |
| Tendons and strands 1-1/2 in. diameter and smaller | 3/4 | ||
| No. 11 bar, W31 or D31 wire, and smaller | 5/8 | ||
| Beams, columns, pedestals, and tension ties | Primary reinforcement | Greater of db and 5/8 and need not exceed 1-1/2 | |
| Stirrups, ties, spirals, and hoops | 3/8 |
20.5.1.3.4
Deep foundation members shall have specified concrete cover for reinforcement at least that given in Table 20.5.1.3.4.
Table 20.5.1.3.4—Specified concrete cover for deep foundation members
| Concrete exposure | Deep foundation member type | Reinforcement | Specified cover, in. |
|---|---|---|---|
| Cast against and permanently in contact with ground, not enclosed by steel pipe, tube permanent casing, or stable rock socket | Cast-in-place | All | 3 |
| Enclosed by steel pipe, tube, permanent casing, or stable rock socket | Cast-in-place | All | 1-1/2 |
| Permanently in contact with ground | Precast-nonprestressed | All | 1-1/2 |
| Precast-prestressed | |||
| Exposed to seawater | Precast-nonprestressed | All | 2-1/2 |
| Precast-prestressed | All | 2 |
20.5.1.3.5
For bundled bars, specified concrete cover shall be at least the smaller of (a) and (b):
(a) The equivalent diameter of the bundle
(b) 2 in.
and for concrete cast against and permanently in contact with ground, the specified cover shall be 3 in.
20.5.1.3.6
For headed shear stud reinforcement, specified concrete cover for the heads and base rails shall be at least that required for the reinforcement in the member.
20.5.1.4 Specified Concrete Cover Requirements for Corrosive Environments
20.5.1.4.1
In corrosive environments or other severe exposure conditions, the specified concrete cover shall be increased as deemed necessary. The applicable requirements for concrete based on exposure categories in 19.3 shall be satisfied, or other protection shall be provided.
20.5.1.4.2
For prestressed concrete members classified as Class T or C in 24.5.2 and exposed to corrosive environments or other severe exposure categories such as those given in 19.3, the specified concrete cover for prestressed reinforcement shall be at least one and one-half times the cover in 20.5.1.3.2 for cast-in-place members and in 20.5.1.3.3 for precast members.
20.5.1.4.3
If the precompressed tension zone is not in tension under sustained loads, 20.5.1.4.2 need not be satisfied.
20.5.2 Nonprestressed Coated Reinforcement
20.5.2.1
Nonprestressed coated reinforcement shall conform to Table 20.5.2.1.
Table 20.5.2.1—Nonprestressed coated reinforcement
| Type of coating | Applicable ASTM specifications | ||
|---|---|---|---|
| Bar | Wire | Welded wire | |
| Zinc-coated | A767 | Not permitted | A1060 |
| Epoxy-coated | A775 or A934 | A884 | A884 |
| Zinc and epoxy dual-coated | A1055 | Not permitted | Not permitted |
20.5.2.2
Deformed bars to be zinc-coated, epoxy-coated, or zinc and epoxy dual-coated shall conform to 20.2.1.3(a), (b), or (c).
20.5.2.3
Wire and welded wire reinforcement to be epoxy-coated shall conform to 20.2.1.7(a).
20.5.3 Corrosion Protection for Unbonded Prestressing Reinforcement
20.5.3.1
Unbonded prestressing reinforcement shall be encased in sheathing, and the space between the prestressing reinforcement and the sheathing shall be completely filled with a material formulated to inhibit corrosion. Sheathing shall be watertight and continuous over the unbonded length.
20.5.3.2
The sheathing shall be connected to all stressing, intermediate, and fixed anchorages in a watertight fashion.
20.5.3.3
Unbonded single-strand tendons shall be protected to provide resistance to corrosion in accordance with ACI 423.7.
20.5.4 Corrosion Protection for Grouted Tendons
20.5.4.1
Ducts for grouted tendons shall be grout-tight and nonreactive with concrete, prestressing reinforcement, grout, and corrosion inhibitor admixtures.
20.5.4.2
Ducts shall be maintained free of water.
20.5.4.3
Ducts for grouted single-wire, single-strand, or single-bar tendons shall have an inside diameter at least 1/4 in. larger than the diameter of the prestressing reinforcement.
20.5.4.4
Ducts for grouted multiple wire, multiple strand, or multiple bar tendons shall have an inside cross-sectional area at least two times the cross-sectional area of the prestressing reinforcement.
20.5.5 Corrosion Protection for Post-Tensioning Anchorages, Couplers, and End Fittings
20.5.5.1
Anchorages, couplers, and end fittings shall be protected to provide long-term resistance to corrosion.
20.5.6 Corrosion Protection for External Post-Tensioning
20.5.6.1
External tendons and tendon anchorage regions shall be protected to provide resistance to corrosion.
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