## 1.4 Concrete and Environment [5.12.1]

### 1.4.1 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
| 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 Bridges*** | 2
Top deck surfaces: Long Bridges***: | 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
Ext. formed surfaces, columns, and tops of footings not in contact w/ water: | 3 | 4
Internal surfaces: | 3
Top of Girder Pedestals: | 2
Substructure (Precast): | 3 | 4
Prestressed Piling (Including cylinder piling): | 3
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 milling. 3- See Short & Long Bridge Definitions in Chapter 4 . 4- See SDG 3.13 for MSE wall cover requirements.

### 1.4.2 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.”

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

### Figure 1-3 Pier in Water (Extremely Aggressive Environment)

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

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