Joint, Contraction

Definition

A contraction joint is a formed, sawed, or tooled groove in a structure designed to create a weakened plane and regulate the location of cracking resulting from the dimensional change of different parts of the structure.

Purpose

The primary purpose of a contraction joint is to control the cracking of concrete or masonry structures by providing predetermined weak points where cracks can form, minimizing random cracking and maintaining structural integrity.

Examples of Use

1. Concrete Pavements: Contraction joints are used in concrete pavements to control cracking due to shrinkage and thermal expansion.
2. Walls and Slabs: In walls and slabs, contraction joints help manage the stresses caused by temperature changes and drying shrinkage.
3. Precast Concrete Elements: Contraction joints are also used in precast concrete elements to ensure cracks form in specific, controlled locations.

Related Terms

• Control Joint: Another term for contraction joint, used to control where cracks occur.
• Expansion Joint: A joint that allows for movement and expansion, accommodating thermal and other stresses.
• Saw Cut: A method of creating contraction joints by cutting grooves in hardened concrete.

Notes

Proper placement and depth of contraction joints are crucial for their effectiveness. They should be spaced and designed according to the specific requirements of the structure and material used.