EXODERMIC™ CONSTRUCTION

A brief explanation of the two ways to construct a deck using the Exodermic™ system, precast or cast-in-place. (See "Representative Projects" for additional photographs and project details.)

GRID FABRICATION

The first step in constructing an Exodermic™ deck is the fabrication of the steel grid portion of the deck by a licensed manufacturer.

PRECAST ERECTION

Pre-cast Exodermic™ decks are an excellent choice where the roadway must be returned to active service as soon as possible. Precasting allows rapid deck replacement during a short, nighttime work window, with roadways fully open to traffic during the day.

During precasting, blockouts or slotted forms exclude concrete from deck panel areas that will be directly over the top flanges of stringers, girders, or floorbeams.

Haunches are generally formed before placing deck panels on the bridge. Self-adhesive foam strips, galvanized sheet steel or structural angles (connected with straps or welded to the supporting beam), and timber have all been used successfully.

Once positioned, panel elevation is set by built-in leveling bolts, headed shear connectors are welded to the superstructure through blockouts in the precast concrete, and this area is filled full depth with rapid setting concrete. The use of 3/8" maximum coarse aggregate is recommended. Alternatively, headed studs may be laid out and welded in position before the deck panels are landed.
If desired, an overlay can be applied after all panels are placed. Latex modified concrete, polymer concrete, microsilica concrete, or a membrane and asphaltic concrete may be specified.

Typical transverse connections between panels are double female shear keys filled with rapid setting grout or concrete after the panels are in place. Field-placed haunch and shear key concrete should be properly consolidated with a ‘pencil’ type vibrator.

Where desirable (such as in areas over supports where negative movements are high), rebar can be spliced between panels by several methods.

CAST-IN-PLACE ERECTION

Cast-in-place Exodermic™ decks are simple and straightforward to erect.

Haunches may be formed before placing deck panels on the bridge, using self-adhesive foam strips, galvanized sheet steel or structural angles (connected with straps or welded to the supporting beam), or timber.

Exodermic™ steel grid panels are placed and set to the required elevation using built-in leveling bolts.

Headed studs are welded or bolted through the grid to the superstructure, rebar is placed, and concrete is poured.

In effect, the steel grid panels act as super ‘stay-in-place’ forms, and little or no additional formwork is required in the field. Rebar layout is straight forward. Bottom rebar (typically #3 bars) sit directly on the main bars. Concrete fills the ‘haunch’ areas, capturing the headed shear studs at the same time the finished riding surface is poured. The use of 3/8" maximum coarse aggregate and a ‘pencil’ type vibrator are recommended.

The concrete can be finished with a textured surface for skid resistance, or any overlay compatible with standard reinforced.