What is Contraction Joint?
These are essentially separations or planes of weakness introduced in concrete structures to localize shrinkage movements, which would otherwise lead to unsightly cracks. These are three types:
a) Complete Contraction Joint:
In this type of joint, the bond between adjacent sections of a structure may be broken completely by painting one face with a bituminous material.
b) Partial Contraction Joint:
When structural stability is required between sections of a reinforced concrete structure separated by a contraction joint it is sometimes convenient to continue the reinforcement across the joint.
c) Dummy joint:
Dummy type contraction joints are used more particularly in thin sections of concrete.