What is the difference between a control joint and a contraction joint in concrete? I mean, a control joint is to control the cracks in concrete due to temperature or shrinkage etc... I understand it. But then what is a contraction joint? I saw this term when I was reading about dams, when they pour large concrete masses and make contraction joint to account for shrinkage. Why don't they also call it a control joint?
They're the same thing. See the link below for an article by the Portland Cement Association. Just different vocab from different regions of the country. Another common example of this in structural engineering is mat slab versus raft slab. They're synonyms.