Expansion joints in buildings are provided to allow the movement of structural members because of temperature variation and moisture content variation.
Expansion joints allow movements of the structural member during temperature variation.
As per IS 456-2000, if the length of the structural member is more than 45 meters then the use of an expansion joint is a must.
Filling material in expansion joint
Natural or cellular rubber, bitumen, expanded plastic or polythene foam could be used as a filling material in expansion joints.
A sealing compound is used to prevent the ingress of water or any other foreign compound in the expansion joint.
Indian standards stipulate the installation of expansion joints in construction in IS 3414-1968, which is reaffirmed in 2000.
Criteria for selection of filling materil
The joint filler must be compressible without extrusion, that is it should be cellular.
The joint filler should regain its 75% thickness as soon as possible after relieving the pressure.
The material should resist weathering as much as possible.
Other types of joints in construction – Construction joint and Contraction joint
When it is not possible to cast the whole construction element as a monolithic one, the construction joints are used.
When it is necessary that the construction joint should be filled up with some material so that cracks do not appear then it is called a contraction joint.
There are three types of contraction joints.
- Complete contraction joint
- Partially contraction joint
- dummy joint