Joint Seals (compression seals): replacements & retrofits 1

[tumbleleaves]

On every detail (Wabo and various DOTs) the joint seal is always shown sitting on top of a neat little step: either a 1/2" strip of metal when the groove is armored or it is placed in the neat sawcut groove.

I wonder if it might be alright to omit the little step that is shown (i.e. place the seal between two flush, vertical surfaces)?
1) When I have seen these installed (without armoring) the groove depth was taken as a minimum and the operator of the saw was not doing precise work. I don't believe the seal was sitting on a neat little step as shown in the pictures.
2) I can only think of two reasons for the step as a restraint to prevent the seal from being shoved down too far during installation, or to keep the seal from being shoved down by say an accumulation of incompressible debris.

My thinking is that the contractor should be able to install the seal without shoving it down too far and that the typical silicone seal with a backer doesn't get shoved down by debris build up--so I am reasoning that it would be alright? I mean it takes a pry bar to get these things to move once installed?

It would greatly simplify construction to not provide the seat/step. Looks like it will be another "judgement" call from my desk...

 

[crossframe]

sawcutting the concrete can correct for thermal movement due to differences in temperature when second "side" of the concrete face is placed. That is, the sawcut width is adjusted to temperature when the seal is installed to get the correct opening size.

Plus, I think that little step provides some resistance years down the line when the adhesive wears out.

 

[tumbleleaves]

Thanks for the response crossframe.

1) I am aware that the width requirement at time of installation is contingent on the bridge's temperature at that time.
2) I question whether the adhesive is necessary on these seals, its primary purpose being to lube the seal so that it can be placed.

I am currently dealing with existing bridges and a limited budget. Creating notches does not appear to be a cost effective solution in several locations.

 

[bridgebuster]

Check with a technicsl rep from the seal manufacturer. Remember, if you deviate from a DOT standard or the manufacturer's instruction and something goes wrong the owner blames you.

BTW - NYSDOT armorless joints don't have the lip.

 

[crossframe]

Lubication or adhesion quality in the future is always a guessing game. The attached photo was taken 23 years after the seal was replaced. I don't know how long it looked like this. At least the condition of the seal is much easier to inspect when it's lying on the beam seat.

 

[tumbleleaves]

Nice photo crossframe.

Some of the failures I am dealing with are caused by seals that were improperly sized or improperly installed.

If the failure in the picture was caused by the compression seal "walking" down to the bottom due to the cyclic back and forth deformation (and with a lack of step/seat to stop it), then my thinking could be wrong.

Do you know or have a guess why the seal in the photo failed?

 

[crossframe]

A new compression seal in an old bridge never seems to last as long as the original. This particular seal was between two steel girder spans. I'm sure both side of the joint moving didn't help. Since it the only one to fail out of of four or five, it probably had more to do with the initial installation than anything else.