Difference Between Expansion joints, Contraction Joint and Construction Joints

Joints are connecting two different elements into one element.

But you may aware that the weakest zone of a structure is “Joint”  so if possible avoid it.

Most of the construction elements has formed by different materials and due to weather conditions that may shrink or expand. 

Different types of joints are used to prevent the concrete cracks from happening by the weather condition.

Today We are going to discuss the different types of joints used in construction works.

Types of Joints in Construction

• Construction Joints
• Expansion Joints
• Contraction Joints

Construction Joints

We cannot pour a larger quantity of concrete at any given time. So at that time, a certain portion has poured as per the recommended shuttering design and the remaining portion will be poured after a certain period.

In that, the construction joints are used to connect the old and fresh concrete and it is also called cold joints.

Specification of Construction Joints

• The existing concrete should have an uneven surface and free from dust.
• A proper vibration has to be done near the joint to develop the proper bond between the old and new concrete.
• After pouring of new concrete the joint surface must be clean out laitance and slurry by the wire brush.

The construction joints are provided as per IS 11817.

The construction joints are advisable to avoid if it is not possible then reduce the number of construction joints.

Expansion Joints

As we discussed, the construction materials are formed from different raw materials. The concrete may shrink or expand due to the weather condition.

In order to avoid any structural failure because of the deformation of construction materials, we use expansion joints.

The expansion joints gap are provided to accommodate the movement happening by the expansion or shrinkages and it is avoiding the disfiguration of the structure.

Mostly the expansion joint gaps are providing in large structure & bridge girder to spread eventual stress. The joint gaps are filled by the expansion material like fibre, bitumen, or some other special material.

Specification

• Expansion joint might be provided in mid of each span in bridges.
• The provision of expansion joints is when the structure length exceeding  45m.
• The reinforcements should not be provided on the expansion joint area.
• The expansion joint material will be different based on the structure.

The expansion joints are provided as per IS 3414.

Contraction Joints

It is another type of joint which controls the cracks happening due to shrinkages. The contraction joints are placed as a groove where the crack may form in concrete. If the shrinkage crack is formed in the concrete slab then the contraction joints prevent spreading on the other area.

Specification

• The width of the groove should not be less than 5mm.
• The contraction joint depth is 1/4th of the Concrete mean depth.
• It should be placed in the weakest zone of the slab.

Another name of the contraction joint is Control Joint.

We hope you may get clarity about the different types of joints in construction. You may like to read Different types of columns.