Contraction Joint

Definition

A contraction joint is a joint between two parts of a structure designed to compensate for the contraction to which either part, or both parts, may be subject.

Purpose

The purpose of a contraction joint is to control cracking in concrete structures by allowing for controlled movement due to shrinkage, temperature changes, or other factors that cause contraction.

Examples of Use

• Sidewalks and pavements incorporate contraction joints to prevent random cracking due to shrinkage.
• Large concrete slabs, such as those in warehouses, use contraction joints to control crack formation.
• Concrete walls and structures exposed to temperature variations use contraction joints to accommodate thermal contraction and expansion.

Related Terms

• Expansion Joint: A joint designed to accommodate expansion as well as contraction in a structure.
• Control Joint: A joint placed in concrete to control where cracking occurs due to shrinkage.
• Isolation Joint: A joint that separates different parts of a structure, allowing independent movement.

Notes

Proper placement and spacing of contraction joints are crucial for effective crack control. The joints should be deep enough to ensure they work as intended and filled with suitable materials to accommodate movement.