Definition - What does Construction Joint mean?
A construction joint is a type of concrete joint that is used when a new section of concrete is poured adjacent to another concrete section that has already set. The purpose of a construction joint is to allow for some horizontal movement, while being rigid against rotational and vertical movement. Construction joints prevent the premature failure of the concrete structure.
Corrosionpedia explains Construction Joint
A construction joint is used when a concrete slab that has already set must be joined with a new section of concrete. There are several reasons why this may be necessary. One is that construction work must pause at some point (e.g., the end of the day), thus one concrete section is inevitably allowed to set before subsequent sets. When work resumes it is desirable for the new section and the old section to act as similar to one large slab as possible.
Construction joints can have several different geometries, including straight wall butt joints and tongue and groove joints.
An alternative method to join a concrete slab that is already set with another concrete slab is to place a tie bar through each, thus connecting them together.