Cast in-situ slabs foundation which are more than ~45 m can not be casted in a single pour of concrete due thermal expansion & project site feasibility issues.
 
✔ Hence the large slabs or raft foundation are casted in different pour phases, allowing some time difference between casting of two pours.
 
✔Joints or details provided between pour phases is referred as construction joint, also construction joints are provided between beam column junction or any two structural members which are connected structural but casted at different times.
 
✔ Construction joints pose challenge not only regards to accurate load transfer across the joint but also for water proofing, construction feasibility.
 
✔These are some important things to focus while detailing a construction joint.
 
–      Development length of the all the rebar at the junction and how to achieve those.
–      If there are any bars which need to be chemically anchored post the concreting
–      Water stoppers or sealant if joint is directly in contact with soil.
 
✔Though the construction joints are not part of analytical model, but it is needed that its effect are factored in during design.
 
The image below shows the location of construction joints between pour phases and a construction joint detail.
 
This is a post on construction joints and their importance. Any comments or suggestions are welcomed.