The allowable procedures for the repair of metalized and galvanized surfaces are described in CMS 711.02, which refers you to ASTM-A-780. The use of a galvanizing spray with zinc dust is not allowed. These unacceptable products go by the name of Spray Galv or Cold Galv. The main problem with these products is that they don’t provide the galvanic protection that we require. Most of them are made out of tin and lead in lieu of zinc. When zinc and carbon steel are in contact the zinc sacrifices itself to protect the steel. Conversely when tin or lead are in contact with the steel the steel actually sacrifices itself for the tin and lead.
It is important that the gap that is set between the armor plates of the joint is consistent along the entire length of the joint. The gap determined for the joint must also be adjusted for temperature. The joint manufacturer will normally supply a table to help calculate this adjustment. This is especially true for the more complex joints.
The characteristics of the structure (skew, crown, super elevation, sidewalk) can lead to a complicated installation of the joints. The Contractor should not be allowed to weld anything to the joint or the reinforcing steel.
Joints like strip seal, compression and modular which incorporate a rubber seal into their design need to have the seals installed per the manufacturer’s written instructions. They should utilize tools that will not cut or puncture the seals. It is not acceptable to elongate or stretch the seal in order to make it narrow enough to fit in the joint gap.
In addition to the protection required in the specification, the Contractor must ensure that the sawcut is not exposed to traffic prior to receiving the sealer without protecting the sawcut. If the sawcuts are not protected rocks, or other hard debris, can get lodged in the top of the sawcut and when this is driven over the rock will spall the edges of the sawcut.
Note that if the beam seats are low and you are utilizing elastomeric bearings it is not acceptable to use steel shims under the bearing to make up the elevation difference. Contact the Office of Structural Engineering for guidance.
Many of the bearings we use have beveled load plates. This is done to account for the grade in the in the structure. Make sure the beveled bearings are oriented correctly. Sometime it is difficult to tell just by looking at the bearing as the difference may only be a ¼”. If the short side of the bearing is not already marked by the fabricator, measure the bearing and marked it in the field.
When galvanized bearings are welded to the embedded load plates on prestressed beams the weld area must be repaired according to CMS 516.03
There is a listing on the Qualified Product List (QPL) for items covered in CMS 711.21. This list is maintained by the Office of Materials Management.
1. Expansion material placed and measured in appropriate unit
2. Joint Sealer
a. Area to be sealed clean and dry
b. Document depth of poured joints
c. Note types of bond breakers and bonding agents used
d. Sealers applied per manufacturer’s directions
e. Measure and pay in appropriate unit
3. Bearing devices
a. Sliding plates lubricated with flake graphite
b. Lead sheets and bearing pads set to line and level
c. Rockers and rollers set vertical at 60° F (16° C) or adjusted for temperature
d. Anchor bolts placed to proper depth and alignment and set in mortar
e. Record quantity(s) and pay in appropriate unit(s)