Expansion joints are generally provided in the
structure after every 50 m.
Generally, premould bituminous sheets are used as a
back-up material and two component polysulphide sealant (base and accelerator)
is used for sealing exterior part of the joint with special primer as a bonding
agent.
Surface preparation for expansion joint waterproofing.
Clean the joint surface of dust, cement mortar etc.
Remove oil grease (if any), from the surface.
Protect the edges of the joint with a masking tape,
from the over filled sealant material.
Keep the tools like suspended scaffolding (zula),
ladder, spatula, putty knife, hand held gun equipment etc. ready.
For waterproofing of the horizontal expansion joint,
arrangement should begin from the R.C.C. stage of the building.
Work procedure for horizontal expansion joint
waterproofing
Inverted beam are taken to the location, for the
expansion joint, side by side.
A cantilever chhajja is provided from the beam, which
is on the rain-side.
Shuttering of the beams is done from one side. Between
the two beams, premould bituminous sheet is placed.
Premould bituminous sheet is also placed beneath the
cantilever chhajja.
The far end of the chhajja is slopes downwards, for
easy drainage of water.
The system is water-proofed with brick bat coba.
Where the parapet walls meet, the same technique is
used and an umbrella type cantilever slab is projected, to protect the joint
from rains.
