Structures Design Guidelines | Jan 2008
1 - General Requirements |

## 1.4 Concrete and Environment [5.12.1] (07/07) July 2007 - Revised A. to require assumption of use of Florida limerock coarse aggregate with 0.9 correction factor.
Jan 2007 - Inserted new 1.4.1 General, including TDB 06-08.

### 1.4.1 General

A. Assume the use of Florida limerock coarse aggregate in design, with K 1= 0.9 as the correction factor when calculating the Modulus of Elasticity in LRFD 5.4.2.4. For Florida limerock, w c is typically taken as 0.145 kcf.

B. In LRFD [5.4.2.6] under "For normal-weight concrete:", in the second bullet, replace the modulus of rupture of 0.37√f 'c with 0.24√f 'c .

Commentary: FDOT has chosen to use the traditional modulus of rupture that has been in the AASHTO specifications since the 1960's.

### 1.4.2 Concrete Cover

Delete AASHTO LRFD 5.12.3 and substitute the following requirements:

A. The requirements for concrete cover over reinforcing steel are listed in Table 1.2. Examples of concrete cover are shown in Figures 1-2 through 1-5.

B. When deformed reinforcing bars are in contact with other embedded items such as post-tensioning ducts, the actual bar diameter, including deformations, must be taken into account in determining the design dimensions of concrete members and in applying the design covers of Table 1.2.

### Table 1.2 Concrete Cover (07/07) July 2007 - Added line for Spun Cast Cylinder Piling (2" cover). Added note 5.
| CONCRETE COVER (inches)
S or M* | E*
Superstructure (Precast)
Internal and external surfaces (except riding surfaces) of segmental concrete boxes, and external surfaces of prestressed beams (except the top surface): | 2
Top surface of girder top flange: | 1
Top deck surfaces: Short Bridges3 | 2
Top deck surfaces: Long Bridge3: | 2 1/2**
All components and surfaces not included above (including barriers): | 2
Superstructure (Cast-in-Place)
All external and internal surfaces (ex. top surfaces): | 2
Top deck surfaces; Short Bridges 3: | 2
Top deck surfaces; Long Bridges 3: | 2 1/2*
Substructure (Precast and Cast-in-Place)
External surfaces cast against earth and surfaces in contact with water: | 4 | 4 1/2
Exterior. formed surfaces, columns, and tops of footings not in contact with water: | 3 | 4
Internal surfaces: | 3
Top of Girder Pedestals: | 2
Substructure (Precast): | 3 | 4
Prestressed Piling: | 3
Spun Cast Cylinder Piling5: | 2
Drilled Shaft and auger cast piles: | 6
Retaining Walls (Cast-in-Place or Precast)(Excluding MSE walls4) : | 2 | 3
Culverts (Cast-in-Place or Precast): | 2 | 3
Bulkheads: | 4
*S = Slightly Aggressive; M = Moderately aggressive; E = Extremely Aggressive. **Cover dimension includes a 0.5-inch allowance for planing. 3- See Short & Long Bridge Definitions in Chapter 4 . 4- See SDG 3.13 for MSE wall cover requirements. 5- Concrete for spun cast cylinder piling to be used in an extremely aggressive environment must have a documented chloride ion penetration apparent diffusion coefficient with a mean value of 0.005 in2/year or less, otherwise 3-inch concrete cover is required. See SDG 3.5.17 for further limits on the use for splicing of these piles.

### 1.4.3 Class and Admixtures

A. The “General Notes” for both bridge plans and wall plans require the clear identification of, and delineation of use for, concrete class and admixtures used for strength and durability considerations.

B. Concrete Class Requirements: When the environmental classifications for a proposed structure have been determined, those portions of the structure located in each classification will be built with the class of concrete described in Table 1-3 for the intended use and location unless otherwise directed or approved by the Department.

C. Unless otherwise specifically designated or required by the FDOT, the concrete strength utilized in the design must be consistent with the 28-day compressive strength given in the FDOT Standard Specification Section 346.

Commentary: Example:

Component - submerged piling

Environment - Extremely Aggressive over saltwater

Concrete Class - Table 1.2 Class V (Special)

Quality Control and Design Strength at 28 days - 6,000 psi

D. Admixtures for Corrosion Protection: Primary components of structures located in Moderately or Extremely Aggressive environments utilize Class IV, V, V (Special), or VI Concrete. These concrete classes use fly ash, slag, silica fume, and/or cement type to reduce permeability.

E. Structures located in Extremely Aggressive marine environments may require additional measures as defined below. These additional measures and their locations must be clearly identified in the “General Notes”. Technical Special Provisions may be required for their implementation.

F. The use of concrete admixtures to enhance durability must be consistent with these guidelines. The Engineer of Record may request additional measures to be approved by the State Corrosion Engineer and the State Structures Design Engineer.

G. When the environmental classification is Extremely Aggressive due to the presence of chloride in the water of a marine environment:

1.) Specify calcium nitrite in all:

a.) Superstructure components situated less than 12 feet above Mean High Water (MHW) .

b.) Retaining walls, including MSE walls situated less than 12 feet above MHW and within 300 feet of the shoreline.

2.) Specify silica fume in all:

a.) Piles of pile bents.

b.) Columns or walls within the "splash zone."

c.) Sections of post-tensioned cylinder piles within the "splash zone" plus one section above and below the "splash zone" limits.

3.) Do not specify silica fume for drilled shafts.

4.) The splash zone is the vertical distance from 4 feet below MLW to 12 feet above MHW.

Table 1.3 Structural Concrete Class Requirements
Concrete Location and Usage | Environmental Classification
Superstructure |  | Slightly Aggressive | Moderately Aggressive | Extremely Aggressive
Cast-in-Place (other than Bridge Decks) | Class II | Class IV
Cast-in-Place Bridge Deck (Including Diaphragms) | Class II (Bridge Deck) | Class IV
Approach Slabs | Class II (Bridge Deck)
Precast or Prestressed | Class III, IV, V, or VI | Class IV, V, or VI
Substructure | Cast-in-Place (other than Bridge Seals) | Class II | Class IV | Class IV, or V
Precast or Prestressed (other than piling) | Class III, IV, V, or VI | Class IV, V, or VI
Cast-in-Place Columns located directly in splash zone | Class II | Class IV
Piling | Class V (Spec.) or VI
Drilled Shafts | Class IV (Drilled Shafts)
Retaining Walls | Class II or III | Class IV
Corrosion Protection Measures: Calcium nitrite and/or silica fume admixtures may be required. Admixture use must conform to the requirements of “Concrete Class and Admixtures for Corrosion Protection.”

See Figure 1-2 End Bent in Slightly or Moderately Aggressive Environment

See Figure 1-3 Pier in water (Extremely Aggressive Environment)

See Figure 1-4 Intermediate Bent in water (Slightly or Moderately Aggressive Environment)

See Figure 1-5 Cast-in-Place Slab with Beam Supported Superstructure (All Environments)