Civil Bhai

◆JOINTS IN CEMENT CONCRETE PAVEMENTS◆

• Due to the changes in atmospheric temperature, the temperature of pavement slab also changes.

• The change of concrete slab temperature causes movement of the slab, thereby inducing stresses in it known as temperature stresses.

• Thus, to minimise temperature stresses in the pavement slab following types of joints are provided in the slab:

a) Expansion joint b) Contraction joint c) Warping joint

• The joints are provided transversely along the full width of the pavement slab. In addition to the above joints, construction joints are also provided.

• The construction joints are provided at the close of day's work and the commencement of the same the next day.

• Generally, concreting is done in one lane width at a time.

• Thus, the two lanes also are jointed together by a joint, known as longitudinal joint.

• Thus, joints may also be classified depending upon the direction of their placement as follows:

1. Transverse joints 2. Longitudinal joints

Transverse joints may further by classified as:
(a) Construction joint (b) Expansion joint (c) Contraction joint (d) Warping joint

Construction joint: These joints are provided where the day's work is finished. They are provided to develop proper bond between the new and old concrete. A construction joint is provided with a key and reinforcing bar as shown in the figure.

Expansion joint: These joints are provided to allow the expansion of concrete slab due to temperature rise. In India expansion joints in concrete pavements are provided at an interval of 18 m to 21 metres. The approximate gap width for this type of joints is provided between 2 to 2.5cm.

Contraction Joint: These joints are provided to accommodate the contraction of the slab. These joints are spaced closer than expansion joints depending upon the type of aggregate used and type of soil sub grade etc.