Precautions to be taken concreting of girders around bearings

Precautions to be taken during concreting of girders around bearings

It has been observed in a number of bridge works that concrete spills over and around the bearings, Joining them and rendering them ineffective. This appears to be the result of improper girder form work in the region of the bearings.

Hence, to ensure against such spilling of concrete the arrangements detailed in the below sketches is recommended for adoption.

Section in Elevation

Cross Section

Extreme care should be taken to see that:

1. The asphalt pad and planks around the bearings abutments against the bearing plate leaving no gap.
2. As an additional precaution 1/16" tar paper is suggested to be laid over the top of the bearing plate.
3. The asphalt pad and planks around the bearing should be removed at the time of striking of girder centering and must not be left in place.

The above arrangement applies to articulations of balanced cantilever girders also.

Note (per IRC:83 Parts I/II/III, IRC:112, and standard practices): Concrete ingress/spillage is a common defect leading to bearing "freezing" (loss of movement capacity), increased stresses, and premature failure. Primary causes include poor formwork sealing, excessive vibration forcing mortar into gaps, high-slump concrete, or inadequate temporary protection. IRC:83 mandates protecting bearings from contamination during concreting; any spilled mortar must be removed before setting. Use tight seals (asphalt pads + tar paper/rubber gaskets) to create a barrier; avoid direct contact of wet concrete with bearing surfaces. Vibration should be controlled (needle vibrators away from bearings) to prevent leakage. Post-concreting inspection: Check for spillage, ensure no bonding to bearing plates, and verify free movement. For balanced cantilever/continuous girders, temporary hold-downs or sequencing may be needed to control uplift during pour. Chamfer sharp concrete edges (as per IRC:112) to reduce spalling risk.

Additional best practices: Before concreting, cover bearings with polythene or temporary caps; use low-slump mix near bearings; apply release agent if needed (but avoid on bearing surfaces). After form striking, clean bearings thoroughly (remove any residue with wire brush/solvent if approved). For elastomeric/pot bearings, ensure full contact and no voids under plates. Regular monitoring during service is essential — frozen bearings can cause girder distress, deck cracking, or substructure overload.