How to form a straight concrete edge during a bridge mill and fill overlay?

[The TKAT]

We are having a problem with the way that contractors are protecting and curing the edge between spans on bridges during an overlay after milling. Right now they are using a piece of Styrofoam, but the piece moves while the overlay is being placed. I have looked for other methods for the gap between spans to be formed during the overlay without any luck. I was just wondering if anyone had a good method for protecting the gap between spans while creating a straight edge along the concrete for a bridge expansion joint system to be placed in.
Thanks,

 

[epoxybot]

I have used A36 Steel Angle for Polyester Concrete Overlays. We would pot them in Hydraulic Cement.

 

[SlideRuleEra]

The TKAT - I assume the joint is open, as used for Neoprene compression seals.

How about lumber forms against each span, held in place by friction for pairs of wooden wedges spaced along the joint. After curing is complete, drive the wedges down and out of the joint to allow removal of the lumber forms.

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[BridgeSmith]

Typically, the deck joints do not go the full depth of the slab, but rather just the depth needed for the elastomeric compression seal (about 2" for the smaller seals).

We typically let the contractor use whatever methods they find suitable to form the blockout. Some have opted to cut the groove with stacked blades on a large concrete saw after the overlay is stiff enough. Some use a heavy-walled rectangular structural tube. They all have their preferred method, which we don't attempt to anticipate or dictate. We just tell them to do it, inspect it when they're done, and tell them if it's acceptable or not.

 

[SlideRuleEra]

Typically, the deck joints do not go the full depth of the slab, but rather just the depth needed for the elastomeric compression seal...

An expansion joint (see the OP) that was not full depth would not be effective.

The bridges using prestressed concrete girders that I worked on as a bridge contractor had full depth deck joints, open space under the joints, and used Neoprene compression seals in the joints.

Other designs, such as reinforced, simple span, flat slabs had open joints, used Neoprene compression seals in the joints, but did not have open space under the joints (slabs supported directly by the caps). My suggestion would not work on those.

http://www.SlideRuleEra.net

 

[BridgeSmith]

Yes SRE, if it's an actual expansion joint, it would have to go the full depth, but for a compression seal a ledge on each side is typically used below the seal to keep it from getting pushed down into the joint. So, the gap in the concrete may be, say 2" at the top, but 1-1/2" below the seal.

I thought the OP was talking about a deck joint (joint in the deck only over a continuous girder). We have many such bridges here. When we can, we get rid of the joints and make deck continuous, but we can't always do that, so we end up using a compression seal over what amounts to a control or contraction joint.