Types Of Concrete Joints:
1. Construction Joints.
2. Expansion Joints.
3. Contraction Joints.
4. Warping Joints.
1. Construction Joints:
These joints are provided where there is a break in construction program. The concreting operation should be so planned that the work is completed in one operation. If, however, it has to be stopped before completion of the entire work, construction joints are provided.
i) Beam: Joint may be located at mid-span or over the center of the column in direction at right angles to the length of the beam.
ii) Columns: Joints should be located a few cm below its junction with the beam.
iii) Slab: Joints may be placed at mid-span or directly over the center of the beams, at right angles to the slab.
2. Expansion Joints:
These joints are provided to allow for expansion of the concrete, due to rise in temperature above the temperature during construction. Expansion joints also permit the contraction of the element. Expansion joints in India are provided at an interval of 18 to 21 m. The open gap of this joint varies between 2 cm and 2.5 cm. Sometimes, to transfer load from one slab to the adjacent slab, dowel bars are also used at suitable intervals at these joints.
3. Contraction Joints:
These types of concrete joints are provided to allow contraction of the concrete. Contraction joints are spaced closer than expansion joints. These joints do not require any load transfer device as it can be achieved by the interlocking of aggregates. However, some agencies recommend use to dowel bars fully bonded in concrete.
4. Warping:
Warping joints are provided to relieve stresses induced due to warping effect. These joints are also known as hinged joints.
